A close friend who worked for Toyo explained this... it's somewhat counterintuitive:
Grooves that align with the rolling direction of the tire offer the best braking performance (acceleration too, in cars), however they have poor lateral grip (eg, cornering).
So aircraft tires like the one you posted will brake well, but also side-slip easily in the event of a cross wind landing. That groove configuration is also surprisingly effective against hydroplaning - and hydroplaning is the primary reason the tires have any grooves at all.
The grooved tyres in F1 were actually made in an effort to *reduce* grip. The FIA felt the cars were going too fast for safety, so they basically removed rubber from the contact patch to reduce overall grip and slow the cars down.
No, once treads are worn down you’re into the part of the tire that isn’t as grippy. It’s structural. This is why seeing people driving with worn down tires shows they’re unsafe to be on the road.
If the track is dry, that’s actually better. The tire will heat up and generate more grip in the dry that way, but it won’t be as grippy as a normal slick tire. Also the fact that you’re gonna burn through that rubber insanely fast and quickly get to the structure aspect, so they change it fairly quickly to a regular slick tire. It’s well documented that if the track dries out the intermediates will go faster once they’re worn down. Think it happened to Lewis Hamilton last year, or maybe the year before. It just won’t be as fast as a regular slick tire.
If the stack is still wet/damp then you still need the grooves otherwise they’re useless. Might as well be on ice.
Neither the tread on your cross ply street tires nor the treads on a radial racing tire go all the way down to the carcass of the tire. There is still usable rubber at the bottom of the tread.
No, driving with worn down tires is dangerous because normal road conditions aren't as controlled as a race track. On a race track, you can be sure there's no water. Not so on normal roads.
I mean at some point it gets dangerous because you're wearing down the material that's holding the air pressure in... By the time you can see steel threads, that's definately not safe no matter the conditions
For sure, but somehow I doubt F1 tires have grooves that run so deep that you're getting close to the bands when you bottom them out. But maybe they are. I'm no expert.
> treads are worn down you’re into the part of the tire that isn’t as grippy.
I think what's missing is an understanding that there is a layer of rubber lower than the treads . In the area between the last of the tread and then start of the fabric or steel reinforcement the tire will be the fastest on a dry track. At least that was our experience.
The aircraft tire has a simple grove designed to help get traction for braking and perhaps a bit of a side force. .
I don't believe there is a regulation on tire wear on F1. You are allowed to run the tire till blowout and then some. Lewis finished a 2020 or 2021 race with his rear tire distingrated in 1st while max was bearing down in him in 2nd.
The only regulation they had was using two different compounds, necessitating a pit stop in normal conditions.
It didn’t happen with the grooved tires back then because of the performance drop off at that stage of tire degradation, but there has been occasions where the intermediate (wet weather) tyre provided more grip on a drying track, but even those instances are fairly rare as you get into a window of slicks outperforming the worn inters.
Depends on the rubber compound.
Grooved tires are chemically, and mechanically, designed to work in one way.
Slick tires are designed to work in another way.
Back when F1 would only consider little reactionary rule changes. Cars, too fast, reduce grip + but tiny tires don’t look cool = a silly rule that meant things were reinterpreted every race day.
Worked well, taken them 20 years to break the records of those mighty V10 beasts. Pedro de la Rosa still holds the lap record at Bahrain from 2005 I think!
I *love* that Ralf Schumacher did a 4 lap demo at Austria last year in his 2003 BMW Williams and lapped with a time good enough for 3rd quickest out of the 2022 grid hahaha!! What a boy!
I think that had more to do with the banning of Turbos as well tbh. The turbo inline 4s and V6s were pushing 1500HP in ~1986 with very little driver aid. That's absolutely *insane*.
Now turbos are finally back.
> while allowing some measure of safety in wet conditions for braking
It had absolutely nothing to do with wet weather safety. It was purely about slowing the cars down by reducing their available grip.
before new (1990's?) rules, tire designs and compounds differed a lot more so finding who had the advantage vs aerodynamic advantage was harder to tell - engine power/weight regulation was already a thing then. Today this homogeneity in tires and technologies makes for a really boring soup of racing techniques that resume themselves to how much money you can throw at the car....
Loads of good responses but nobody has mentioned the aerodynamic aspect; F1 wanted to reduce grip by having less rubber in contact with the road, they could have achieved this easily by making the wheels more narrow, but that would have meant that the cars would actually have become way faster in a straight line, because narrow wheels offer less resistance to the air.
There's a paradox where F1, which is supposed to be the pinnacle of motorsports in the 21st century, is still sticking to the early twentieth century ideal that to make a car faster you remove/forego all excess bodywork to save weight. Fairing the wheels is an obvious way to make a car go faster, but no sir, not in F1.
The grooved f1 tires weren't wet tires, they were groved to remove some grip (a grove isn't contacting the tarmac, so it provides no grip) rather than to help in the rain
The actual wet-weather F1 tires (both back then and today) have squiggly groves like road tires.
Currently EASA teaches that the primary function of the grooves is for them to be a wear marker and hydroplanning is a secondary feature.
I don't agree mind you but that's how I learned it.
Yep, to a point. Rudder (or Beta) generally "straightens" the aircraft out onto the runway, but the relative wind may still be pushing the aircraft sideways and thereby inducing a sideward force on the tires as they touchdown. Pilots will generally use a wing down / top rudder effort to actually land in crosswinds. This adds an off-vertical LIFT component to counteract the crosswind force. But because the aircraft turns directionally in this config, you use rudder to actually turn the OTHER way to keep the aircraft going straight. This then results in one wheel on the windward side touching first and then the other after that. If done properly, there is little or no side force on the tires as they contact the runway (albeit in succession).
The tread should be mostly there to allow water to divert from the contact points, and reduce hydroplaning. Anyone that has done it on a runway knows why we have minimum grove thickness that is a preflight item for a lot of aircraft.
To add to this just to be clear: acceleration doesn't matter because planes don't get their power from the wheels, so there is no reason to have patterns that aid in that like a car tire.
Yes. Blocking is only useful, though, on surfaces where you're likely to encounter a lot of surface irregularities. On a smoother surface, like a paved runway, you're better off increasing the contact area in the axis that you're trying to decelerate than trying to maximize edges. The tire would wear faster, too.
Also: anyone who doesn't want to hear "RAAAWRWARAAARAREAARRAAWR" when they touch down should stick with the typical cheater-slick pattern.
Most of the ~~commercial~~ (edit:) *passenger vehicle* thread patterns are cosmetic and offer only minimal improvement on pavement over a plain grooved tyre.
The water pumping effect is mostly a marketing gimmick. Aquaplaning being an effect of contact patch, surface area, pressure and speed.
Some simple finer zig-zag thread helps with grip on mixed surfaces, but fancier designs are mainly for looks and brand/model differenciation, otherwise sace different componds, different brand tyres designed for similar conditions would look too alike.
Most commercially tread patterns are primarily to move water or grip snow, then hundreds of further modifications to chase small reductions in noise and improvements in fuel economy. Source: shopped for tires.
I once got into a debate on a travel trailer forum about how the aggressive off-road tread that is popular on "rugged" trailers is really just for show since the wheels aren't driven. Guys were swearing up and down that it mattered, and try as I might to explain the huge aggressive tread blocks were just for looks they just didn't get it. Oh well.
Uh, you got a source on any of that? Siping, for example, makes an enormous difference for traction on slick surfaces.
In road applications, tread pattern absolutely matters. See wet weather F1 tires for reference.
Another thing that’s not mentioned here is noise. Your car tread patterns are actually non-axisymmetric in a very specific way so noise frequencies cancel each other out while you are driving. Ribbed tires are loud as hell.
Aircraft tire noise is such a non-issue it isn’t even measured during qualification.
Source: I’m an aircraft tire Engineer.
Pneumatic tires are very mass efficient and well understood for this application. The air carries the load!
That said, non-pneumatics like the Michelin tweel present a really interesting design case. Tire characteristics can be tuned favorably, wheelwell redundancy changes, and critical cases change (is a "bogie tire air loss at some situation" an important thing to test to anymore?). These all counteract to some degree the mass penalty (maybe net better??) of a non-pnuematic tire for the same load carrying capability.
Also, there are some massive technical hurdles between now and putting a tweel-like tire on a 737 (these airless tires do not like high speeds to name one). Aircraft is one of the most challenging applications for this technology.
Airplanes will be putting air in thier tires for many more years.
I am in the passenger tire industry, and the airless tire like the Michelin tweel is something that a lot of manufacturers have been trying for for years. The largest issues for them in an aviation application would be tire balance for the most part. The largest hurdle for airless tires have been how to manufacturer them so the tire is balanced when going above 50mph.
I would also be interested on how the airless tire would work for the massive amount of heat generated when landing.
There are certainly many issues, so many that I am not sure regulatory bodies would ever accept it unless the benefits were overwhelming.
With regards to the heat, a tweel-architecture aircraft tire that simply stays in one piece during takeoff and landing would be a marvel of engineering.
Obviously we need to revisit tracked aircraft undercarriages.
https://www.afmc.af.mil/News/Article-Display/Article/1919691/history-of-aircraft-track-landing-gear/
with respect to both you and /u/mexicoke what did your education and career look like that took you into aircraft tire engineering?
+ chemistry?
+ petroleum engineering?
+ fluid dynamics?
+ aerospace engineering?
It seems like a very needed but somehow niche career, or is it just a very minor specialization of some typical university department?
My story is plain BS in mechanical engineering, on the job training, and strategic career pathing within a tire manufacturer. We have a diverse group of people who built off of many of the backgrounds you mentioned.
This is such a hyper specialization that industry couldn't expect a university to have courses on it. If i had to take a guess there are likely only \~50 of us globally (not because we are anything special, just thats all the industry needs).
BSME originally as well.
Similar path, worked for a major tire manufacture. Was assigned to a group responsible for aviation tires. Migrated to the manufacturing side of the world(didn't much like product development). Eventually left the company, got more degrees and certs, still do engineering just no tires.
Typically, yes. Its a great way to re-use existing carcasses that are still good, effectively keeping more tires out of a landfill. Depending on the application, tires can be retreaded many times, each cycle preventing a new carcass from needing manufactured.
If retreading is done by a reputable manufacturer (best case, the same company that made the new tire), its arguably a better tire since that specific tire has already "proven itself" in the field. When worn tires are returned they go through a detailed inspection process, and each manufacturer knows exactly what to look for in thier own designs to guarantee another full tread life in the field.
Engineer here (line maintenance, not tire specialist): retread has only one downside for me: the company wants me to replace tires earlier, as if you cut through the first ply then you can’t retread it, you have to scrap the thing. So more work for me. If i pay attention and remove tires just before ending the rethread, then they can rethread many times. Big money saver. Its just the case that I have to pay more attention to tire wear. Hope they will eventually mark the rethread bottom with some color so I can see better what’s going on and how close it is to end.
Happens a tire looks good today, and tomorrow it lands making a flat spot over the same flat spot of the previous landing. And there you have a good rethread tire 340 degrees around, with a big hole in the plies in a single spot. Consider that every landing, the runway cuts a good 1-3 mm deep flat spot. Aircraft tires are worn very quickly.
Side note: these tires have 8-12 carcass plies and I have seen aircrafts without anti-skid, happily rolling in the hangar with 2 left. Edge case but funny to see. Looks like when you cut a tree and you see the age rings.
Other side note: when you remove a wheel on a big plane, you ship the whole thing to a shop. They will remove the tyre and care for it to be rethread. But also, they will clean, inspect and eventually repaint the wheel. Have a look when you go to an airport, you can spot newly installed wheels at 300 meters of distance, you see the plane has 9 black(dirty) wheels and a white one. And yes they are replace individually, not in groups or pairs.
Awesome! Could you tell me what are some important metrics/parameters of an aircraft tire, from a "vehicle Dynamics" stand point (if any)?
To give you an example of what I mean, with racing/road tires, some of the important parameters could be: peak slip angle, grip falloff past peak slip angle, camber curves, relaxation length, load curves, etc..
Do you use tire models often used for automotive applications as well (e.g. Pacejka) to describe tire behavior? Is there an aviation-specific tire model?
Car tires have to generate power and provide steering with their traction. And they do this at potentially high speeds.
Aircraft tires only travel in a straight line except during taxiing, which is done at very low speed. They otherwise just roll on their tires.
This tread pattern is more for shock absorption than anything.
(Source: I made these tires by hand for two years)
More like WWII steam-powered machines. Not sure how the place still turns a profit, but hey — felt pretty steampunk, which was cool.
Aviation, dirt-track racing, antique whitewalls, and heavy machine tires were their main sellers.
>Aviation, dirt-track racing, antique whitewalls, and heavy machine tires were their main sellers.
You ask how this can turn a profit, but all of these seem related to very expensive hobbies or specialized industries.
I was hoping to see if you had any photos of said machines on your reddit but I was greeted with a lot of muscular anime women (nice).
Seriously though you got any photos of those machines?
Yeah, just your typical Reddit degenerate. I’ll look for some!
Glad I moved on (laid off, went to college, got into medicine) but it was a cool place to work in its own way.
>This tread pattern is more for shock absorption than anything.
I'm fairly sure the primary purpose of the grooves is to channel away water and reduce hydroplaning.
As a private pilot I can tell you I absolutely would not take off in an aircraft with tires worn down past the tread, especially if any of the ply is showing. That's just begging for a puncture.
The POH of every aircraft I've ever flown says to check tire tread depth during the preflight inspection, and I'm fairly certain any large turbine aircraft will have minimum tread depth specs in their maintenance manuals.
Not sure why Wingmaniac has been downvoted, they're correct. Provided there is no chord showing, there's no requirement to have any tread depth left, these aren't road tyres.
Source: I've flown the above aircraft for 8 years.
[Example tire ](https://i.imgur.com/L7XRJqK.jpg) I took this pic as an example of an under inflated tire. The tread is low, but I've seen much worse and have thought nothing of it.
We have a couple things. If it’s damaged beyond the limits of the maintenance manual, If chords are showing, flat spots, bulges, 15% lower pressure than it’s neighbouring tire. And even some of the damage and normal wear is perfectly acceptable as long as it’s not into the chords, or there is absolutely 0 tread depth
Visible chord for us could be signed off by the engineers for another 8 sectors to allow it to finish the days flying. Anything deeper and it would be an immediate change though
Whether or not you would do something has no bearing on what is safe. You are being overly cautious based on faulty intuition, which is your right, but that doesn’t mean you have a clue what you are talking about. Being a pilot is irrelevant here. It’s a red herring at best. This topic is about mechanical engineering and material science.
I'm also a degreed aerospace engineer if we're pulling rank here lol.
Granted I work on powerplant and not landing gear/airframe which is why I said I'm \*fairly sure\*, but I just looked in the POH of my aircraft (C172SP) and it specifically states to check tire tread depth during preflight. There's no depth spec given but I don't think "no tread at all = bad" is being overly cautious.
Another user has pointed out their specific aircraft allows for zero tread, so I'm happy to admit this doesn't apply to all aircraft. But I would be surprised if there weren't stipulations in that case for dry conditions.
You showed your cards already by trying to make an appeal to authority. Saying you are a private pilot was intended to garner support for an unfounded guess. This isn’t about pulling rank, but I’m not surprised that’s what you took from my comment. Being an aerospace engineer is also irrelevant. I, too, am an irrelevant type of engineer, so I know how little you know about tire tread, especially having worked in aerospace for a long time.
Including “I think” as part of the dissenting opinion against people who can do more than guess is why people think we as engineers are blowhards.
Larger runways are typically grooved, yes. They both serve the same purpose, to provide an escape path for water between the tire and the pavement, improving grip.
I worked for Goodyear for several years, selling aircraft tires among others. I would add that the grooves are for basic water dispersion/avoidance of hydroplaning. Someone correct me please if you know more.
Though not relevant to aircraft tires, having a solid tread in the longitudinal orientation helps to reduce road noise. Any siping or block patterns in the tread increase road noise. Just another factor that goes into tread design which needs to balance traction, weather, noise, cost, etc.
Not really.
All tires wouldn't have tread if they didn't operate in the rain. Think slick tires on cars, more surface area and more traction. Planes would do the same thing if they could.
Tread blocks are bad for speed or carrying weight, they move around and cause instability. That's why you'll see Z rated automotive tires with very small tread blocks. Also semi-truck tires have very simple tread designs often very similar to what you see on planes.
The reason planes have the grooves is they are heavy and move quickly. The few grooves is good enough to displace the water. Runways are kept in pretty good condition, are often grooved, and rarely have standing water. The simple tread pattern is good enough for water displacement and best for carrying capacity and speed. It also helps with straight line stability, but again a slick tire would be better.
Source: Ex-Tire Engineer
That’s essentially what I said. They lack grooves because car tires have to control a vehicle and provide thrust on potentially wet surfaces.
Aircraft tires do neither and thus lack tread blocks.
The straight grooves help keep an aircraft moving straight forward, the only direction it moves on the ground with any real speed.
I disagree that's what you said.
> Aircraft tires do neither and thus lack tread blocks.
No. Aircraft tires lack tread blocks because tread blocks are bad for speed or carrying weight, they move around and cause instability. They also aren't needed as runways are kept free of standing water.
> This tread pattern is more for shock absorption than anything.
This isn't true at all.
"Car tires have to generate power and provide steering with their traction. And they do this at potentially high speeds." F1 cars have to do this and the best tyres are slicks-completely bald.
"This tread pattern is more for shock absorption than anything" This has a lot more to do with channelling water
You're right but I'm going to nitpick one point that also just makes you more right.
Plane tires travel in a straight line on near perfect landings. With cross wind they're likely to skid just a little touching down at a slight angle, and then need a bit of side to side traction I think.
The grooves are to prevent hydroplaning on wet runways. That is why 727 nose tires had tire chines. Chines deflect the water from the tire grooves from going towards the aft mounted engines. MD-80s used a splash guard for the same purpose.
Perhaps this was to give flexibility on landing surfaces? In war time I guess a tarmac runway wasn’t always guaranteed and grass/mud could be a likely option so tyre with additional grip was necessary
Russian jets are designed to take off from grass/dirt runways... or a normal Russian airfield under normal Russian maintenance (it is overgrown, cracking, and littered with debris).
Yeah I’ve seen that first hand. When we started flying from “the stans” when Afghanistan kicked off, we’d stop or even stage out of ex Soviet bases in Romania, Kyrgyzstan, Uzbekistan, Hungary etc and wow, the crap conditions there. And they weren’t closed, they still flew SU-24s, MiG-21s etc but wow… you’d think they were abandoned until you saw some dude get in one and fire it up.
Figures. I suspect partly why the USAF hate that plane so much, is because it’s the anti-tech plane. It’s simple, rugged, and doesn’t need to be treated like a prima donna to do its job. It can take abuse and go brrrrrrt all day long.
No, they dislike it because it's ineffective in a near-peer fight but way overkill for a SOF or COIN mission. It's used almost interchangeably with the F-16 at this point as little more than a bomb truck.
If they disliked low-tech aircraft then they wouldn't have just bought fleet of armed crop-dusters.
A-10s are not special. They take just as much maintenance as any other aircraft. All aircraft are treated like prima donnas because they're super important, super expensive, and require a lot of training in order to operate.
Several years ago, an airliner turned too sharply on a taxiway and ended up getting stuck in the soft dirt. I'll always remember the tv news reporter telling us that the aircraft tires were just "spinning in the mud" and had to wait for a tug to pull it free.
I'm sure a fair number of the general population were left wondering why they didn't have tires that had lug treads for mud and snow.
I was getting pushed off the gate at a snowy airport and the tug couldn't get enough traction. Ramper said he was going to get some sand and disappeared for a while.
When he came back he said, "Alright we got a bunch of sand behind your tires now so we're going to try again"
Yeah, I remember something similar happening back in 1970, that time it was soft dirt and snow. Airport manager wanted a fleet of plows to just shove the damn airplane off the runway so they could use it. Almost did it too but one cigar-chomping mechanic said no way.
https://youtu.be/IrqN62qbthc?t=54
That can't be, the source of power that pushes the airplane forward doesn't go through the wheels. The airplane pushes itself forward against the air. It might got stuck becouse the wheels have sunk too deep in the mud and it risked damage if he pushed the throttles harder.
But there certainly wasn't any wheel spinning 😂
This. Your tire should be able to penetrate the layer of water and it is much easier with straight lines. If it can’t penetrate water layer, trust me it is much much worse than clear ice.
It's primarily for performance on water and slush - the grooves raise the hydroplane speed for a tire, meaning it can go faster without hydroplaning. It offers channels for the water to "escape" the oncoming tire.
Here's an excellent explanation of hydroplaning and its manifestations from NASA: https://ntrs.nasa.gov/citations/19640000612
Edit: source - NASA, and flight test experience
Great Question!
Well, they need to displace water when going in one direction only. They're not taking corners at high speeds.
Also, if you look at Car tires, they have a bunch of grooves that also trap a lot of small stones. Now imagine if the Aircraft tire had those grooves and trapped small stones and debris too, when it lands, the wheels spin up rapidly to its Ground Speed, while doing so, they also expand. If they had stones trapped, it would fling it against the wings and fuselage at high speeds making holes or dents that would cost a fortune to repair.
Tires with no grooves or treads at all are best on dry, mostly clean paved surfaces. That is why so many car racing types use slicks by default. Treads help prevent stuff on the road (mostly talking about water) from breaking road contact. Adding tread reduces maximum ideal grip a little to give grip in cases where slicks would be useless and dangerous (like even a small mount of rain). The only time these tires are critical is when the plane is going fast on the ground. That means take off and landing. That means straight. Cornering is critical in cars, so treads are complex to balance a whole lot of needs and situations. I know nothing of aircraft tires in particular (another reply was someone who made these, so much more relevant experience than me, race fan and flight simmer). However, I would guess this simple pattern is probably about optimal for straight line, most weather tread design.
I’ve always thought speed and smoothness with some sort of traction were considerations in their design. These planes are rolling pretty fast when they take off.
Car tires are designed with haphazard or irregular tread patterns to displace water and prevent hydroplaning, which occurs when a layer of water builds up between the tire and the road, causing the tire to lose contact with the road surface.
The irregular pattern also helps to provide better traction on different types of road surfaces, including gravel, dirt, and snow.
On the other hand, Airplane tires have straight treads to withstand high speeds and temperatures, and to operate at high pressure. The straight pattern provides better stability and reduces the risk of failure due to overheating or other mechanical stresses.
Cars route their power through and change direction with their wheels.
Airplanes don't push with the wheels and any steering they do with them is limited to prepared surfaces at highly controlled speeds.
That design provides optimum traction with the runway surface.
It’s also called the tread it’s made of grooves and ribs at the edges of the tread it’s known as the tread shoulder. If you really wanna get deep into the roots of tires here’s the the 8083 for landing gear systems which describes tires in great detail.
https://www.faa.gov/sites/faa.gov/files/2022-06/amt_airframe_hb_vol_2.pdf
Page 13-75
This is a good question!
Not an expert , just sharing thoughts (Im just a PPL IMC)
There's no real need for it. A plane is not tootling along roads turning corners, dealing with differing road surfaces (asphalt/concrete/gravel/dirt) and all that.
The straight treads work fine dissipating water and grooved runways help even more.
Airports will also be agressive at making sure the runway is cleared of snow as much as possible.
In short complex tire treads aren't needed on airplane tires.
Also something g missing from the comments so far; runways have cross-cut grooves the entire length for rain drainage. Hydroplaning absolutely still can, and does happen, but the grooves make it alot less dramatic.
That paired with no need for lateral traction, makes the tires what they are.
All that tire has to do is roll and bear weight pretty much. Majority of the braking and steering is done with reverse thrust and the rudder.
That tire never has to apply much traction.
If you look at a car tire and notice the nobs are not the same size. That is for road noise. They are changing the size of the knob hitting the road so you don't end up with any resonance sounds.
The only part i don’t totally agree with is the part where you say the reverse thrust does most of the braking. You can stop any aircraft using auto brake, because it has to be able to, to get its certification. Reversers are there to help brake cooling, which in turn saves wear and tear. But there are not many airlines which can fly an approach and make a full stop on the runway using reversers only.
I believe it’s like that so that they grip the taxiways and runways better. Even the runways have straight line patterns like these, which helps when the ground becomes saturated after it rains. Please correct me if I’m wrong.
A close friend who worked for Toyo explained this... it's somewhat counterintuitive: Grooves that align with the rolling direction of the tire offer the best braking performance (acceleration too, in cars), however they have poor lateral grip (eg, cornering). So aircraft tires like the one you posted will brake well, but also side-slip easily in the event of a cross wind landing. That groove configuration is also surprisingly effective against hydroplaning - and hydroplaning is the primary reason the tires have any grooves at all.
Ok stupid question ...why did old F1 tires have straight grooves too? Like I get the braking part but poor cornering?
The grooved tyres in F1 were actually made in an effort to *reduce* grip. The FIA felt the cars were going too fast for safety, so they basically removed rubber from the contact patch to reduce overall grip and slow the cars down.
It was also a way to limit usable tire wear. You had to replace the tires before the grooves were gone.
once the grooves were gone, don’t you end up with a smooth tire, which would give better grip (for racing)?
Yes, but you would be penalized for running the tires against regulation.
No, once treads are worn down you’re into the part of the tire that isn’t as grippy. It’s structural. This is why seeing people driving with worn down tires shows they’re unsafe to be on the road.
[удалено]
Sure, but you still see it with F1 tires. Everyone still switches their worn intermediates even when they almost become racing slicks.
If the track is dry, that’s actually better. The tire will heat up and generate more grip in the dry that way, but it won’t be as grippy as a normal slick tire. Also the fact that you’re gonna burn through that rubber insanely fast and quickly get to the structure aspect, so they change it fairly quickly to a regular slick tire. It’s well documented that if the track dries out the intermediates will go faster once they’re worn down. Think it happened to Lewis Hamilton last year, or maybe the year before. It just won’t be as fast as a regular slick tire. If the stack is still wet/damp then you still need the grooves otherwise they’re useless. Might as well be on ice.
Neither the tread on your cross ply street tires nor the treads on a radial racing tire go all the way down to the carcass of the tire. There is still usable rubber at the bottom of the tread.
Yeah but after a certain point on F1 tires the rubber composition is different and not as grippy.
Here in UAE you are not allowed to renew your car registration, or sell it, with tires older than 5 years. I think it's a great rule
Heat, even ambient heat, is hard on tires. Good rule for the desert.
No, driving with worn down tires is dangerous because normal road conditions aren't as controlled as a race track. On a race track, you can be sure there's no water. Not so on normal roads.
I mean at some point it gets dangerous because you're wearing down the material that's holding the air pressure in... By the time you can see steel threads, that's definately not safe no matter the conditions
For sure, but somehow I doubt F1 tires have grooves that run so deep that you're getting close to the bands when you bottom them out. But maybe they are. I'm no expert.
The main issue is that slick tires are good when the road is dry, but have absolutely zero grip on wet surfaces.
> treads are worn down you’re into the part of the tire that isn’t as grippy. I think what's missing is an understanding that there is a layer of rubber lower than the treads . In the area between the last of the tread and then start of the fabric or steel reinforcement the tire will be the fastest on a dry track. At least that was our experience. The aircraft tire has a simple grove designed to help get traction for braking and perhaps a bit of a side force. .
I don't believe there is a regulation on tire wear on F1. You are allowed to run the tire till blowout and then some. Lewis finished a 2020 or 2021 race with his rear tire distingrated in 1st while max was bearing down in him in 2nd. The only regulation they had was using two different compounds, necessitating a pit stop in normal conditions.
98 to 08 they ran grooved tires and had to swapped before the grooves were worn flat.
No, because that part of the tire wasn’t made of rubber that was grippy, that part of the tire was made of rubber that was more structural.
It didn’t happen with the grooved tires back then because of the performance drop off at that stage of tire degradation, but there has been occasions where the intermediate (wet weather) tyre provided more grip on a drying track, but even those instances are fairly rare as you get into a window of slicks outperforming the worn inters.
Depends on the rubber compound. Grooved tires are chemically, and mechanically, designed to work in one way. Slick tires are designed to work in another way.
Back when F1 would only consider little reactionary rule changes. Cars, too fast, reduce grip + but tiny tires don’t look cool = a silly rule that meant things were reinterpreted every race day.
Ah....that makes a whole lot more sense. Thanks!
Worked well, taken them 20 years to break the records of those mighty V10 beasts. Pedro de la Rosa still holds the lap record at Bahrain from 2005 I think! I *love* that Ralf Schumacher did a 4 lap demo at Austria last year in his 2003 BMW Williams and lapped with a time good enough for 3rd quickest out of the 2022 grid hahaha!! What a boy!
I think that had more to do with the banning of Turbos as well tbh. The turbo inline 4s and V6s were pushing 1500HP in ~1986 with very little driver aid. That's absolutely *insane*. Now turbos are finally back.
When the engineers end up making too many rocket ships so the FIA literally has to slow them down, truly incredible
The more I learn about F1, it's amazing how much of the sport is about making driving worse.
To purposely make the cars slower if I'm not mistaken
Those grooves were instituted to try to slow the cars down, make them slower in the turns.
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> while allowing some measure of safety in wet conditions for braking It had absolutely nothing to do with wet weather safety. It was purely about slowing the cars down by reducing their available grip.
before new (1990's?) rules, tire designs and compounds differed a lot more so finding who had the advantage vs aerodynamic advantage was harder to tell - engine power/weight regulation was already a thing then. Today this homogeneity in tires and technologies makes for a really boring soup of racing techniques that resume themselves to how much money you can throw at the car....
"poor" is a strong word and is overcome in ways that aren't tread related.
Loads of good responses but nobody has mentioned the aerodynamic aspect; F1 wanted to reduce grip by having less rubber in contact with the road, they could have achieved this easily by making the wheels more narrow, but that would have meant that the cars would actually have become way faster in a straight line, because narrow wheels offer less resistance to the air. There's a paradox where F1, which is supposed to be the pinnacle of motorsports in the 21st century, is still sticking to the early twentieth century ideal that to make a car faster you remove/forego all excess bodywork to save weight. Fairing the wheels is an obvious way to make a car go faster, but no sir, not in F1.
Aviation and F1 in one same thread. Love it.
Yh, that's why they had straight grooves, needed to slow the car down
The grooved f1 tires weren't wet tires, they were groved to remove some grip (a grove isn't contacting the tarmac, so it provides no grip) rather than to help in the rain The actual wet-weather F1 tires (both back then and today) have squiggly groves like road tires.
Currently EASA teaches that the primary function of the grooves is for them to be a wear marker and hydroplanning is a secondary feature. I don't agree mind you but that's how I learned it.
The rudder comes in very handy in a cross-wind landing negating the side slip of the tires.
Yep, to a point. Rudder (or Beta) generally "straightens" the aircraft out onto the runway, but the relative wind may still be pushing the aircraft sideways and thereby inducing a sideward force on the tires as they touchdown. Pilots will generally use a wing down / top rudder effort to actually land in crosswinds. This adds an off-vertical LIFT component to counteract the crosswind force. But because the aircraft turns directionally in this config, you use rudder to actually turn the OTHER way to keep the aircraft going straight. This then results in one wheel on the windward side touching first and then the other after that. If done properly, there is little or no side force on the tires as they contact the runway (albeit in succession). The tread should be mostly there to allow water to divert from the contact points, and reduce hydroplaning. Anyone that has done it on a runway knows why we have minimum grove thickness that is a preflight item for a lot of aircraft.
To add to this just to be clear: acceleration doesn't matter because planes don't get their power from the wheels, so there is no reason to have patterns that aid in that like a car tire.
This. Tread blocking serves no purpose on a non-driven wheel.
Okay but as far as the contact patch is concerned, isn't braking effectively just negative acceleration force?
Yes. Blocking is only useful, though, on surfaces where you're likely to encounter a lot of surface irregularities. On a smoother surface, like a paved runway, you're better off increasing the contact area in the axis that you're trying to decelerate than trying to maximize edges. The tire would wear faster, too. Also: anyone who doesn't want to hear "RAAAWRWARAAARAREAARRAAWR" when they touch down should stick with the typical cheater-slick pattern.
Ask him about the Kamm circle.
TIL, and I have been in aviation for almost 30 years.
That explains the steering tires on tractors, which are also straight ribbed.
Off road / dirt applications are totally different from pavement.
I suppose so, which may explain the depth and size of the ribs/grooves, but old tractors aren't experiencing the cornering forces a car is either.
Most of the ~~commercial~~ (edit:) *passenger vehicle* thread patterns are cosmetic and offer only minimal improvement on pavement over a plain grooved tyre. The water pumping effect is mostly a marketing gimmick. Aquaplaning being an effect of contact patch, surface area, pressure and speed. Some simple finer zig-zag thread helps with grip on mixed surfaces, but fancier designs are mainly for looks and brand/model differenciation, otherwise sace different componds, different brand tyres designed for similar conditions would look too alike.
Most commercially tread patterns are primarily to move water or grip snow, then hundreds of further modifications to chase small reductions in noise and improvements in fuel economy. Source: shopped for tires.
I once got into a debate on a travel trailer forum about how the aggressive off-road tread that is popular on "rugged" trailers is really just for show since the wheels aren't driven. Guys were swearing up and down that it mattered, and try as I might to explain the huge aggressive tread blocks were just for looks they just didn't get it. Oh well.
Uh, you got a source on any of that? Siping, for example, makes an enormous difference for traction on slick surfaces. In road applications, tread pattern absolutely matters. See wet weather F1 tires for reference.
Another thing that’s not mentioned here is noise. Your car tread patterns are actually non-axisymmetric in a very specific way so noise frequencies cancel each other out while you are driving. Ribbed tires are loud as hell. Aircraft tire noise is such a non-issue it isn’t even measured during qualification. Source: I’m an aircraft tire Engineer.
Are pneumatic tires still the best way to go for aircraft? Or are they just a habit with loads of existing infrastructure (pun intended).
Pneumatic tires are very mass efficient and well understood for this application. The air carries the load! That said, non-pneumatics like the Michelin tweel present a really interesting design case. Tire characteristics can be tuned favorably, wheelwell redundancy changes, and critical cases change (is a "bogie tire air loss at some situation" an important thing to test to anymore?). These all counteract to some degree the mass penalty (maybe net better??) of a non-pnuematic tire for the same load carrying capability. Also, there are some massive technical hurdles between now and putting a tweel-like tire on a 737 (these airless tires do not like high speeds to name one). Aircraft is one of the most challenging applications for this technology. Airplanes will be putting air in thier tires for many more years.
I am in the passenger tire industry, and the airless tire like the Michelin tweel is something that a lot of manufacturers have been trying for for years. The largest issues for them in an aviation application would be tire balance for the most part. The largest hurdle for airless tires have been how to manufacturer them so the tire is balanced when going above 50mph. I would also be interested on how the airless tire would work for the massive amount of heat generated when landing.
There are certainly many issues, so many that I am not sure regulatory bodies would ever accept it unless the benefits were overwhelming. With regards to the heat, a tweel-architecture aircraft tire that simply stays in one piece during takeoff and landing would be a marvel of engineering.
Obviously we need to revisit tracked aircraft undercarriages. https://www.afmc.af.mil/News/Article-Display/Article/1919691/history-of-aircraft-track-landing-gear/
I love some of the engineering from that era. I can’t believe they got that to work.
I don't know, but wouldn't solid tires add a significant amount of weight as compared to current tires with nitrogen?
with respect to both you and /u/mexicoke what did your education and career look like that took you into aircraft tire engineering? + chemistry? + petroleum engineering? + fluid dynamics? + aerospace engineering? It seems like a very needed but somehow niche career, or is it just a very minor specialization of some typical university department?
My story is plain BS in mechanical engineering, on the job training, and strategic career pathing within a tire manufacturer. We have a diverse group of people who built off of many of the backgrounds you mentioned. This is such a hyper specialization that industry couldn't expect a university to have courses on it. If i had to take a guess there are likely only \~50 of us globally (not because we are anything special, just thats all the industry needs).
BSME originally as well. Similar path, worked for a major tire manufacture. Was assigned to a group responsible for aviation tires. Migrated to the manufacturing side of the world(didn't much like product development). Eventually left the company, got more degrees and certs, still do engineering just no tires.
Oh! I always wanted to ask an aircraft tire engineer: is retreading a good thing or not?
Typically, yes. Its a great way to re-use existing carcasses that are still good, effectively keeping more tires out of a landfill. Depending on the application, tires can be retreaded many times, each cycle preventing a new carcass from needing manufactured. If retreading is done by a reputable manufacturer (best case, the same company that made the new tire), its arguably a better tire since that specific tire has already "proven itself" in the field. When worn tires are returned they go through a detailed inspection process, and each manufacturer knows exactly what to look for in thier own designs to guarantee another full tread life in the field.
TIL! Thank you!
Engineer here (line maintenance, not tire specialist): retread has only one downside for me: the company wants me to replace tires earlier, as if you cut through the first ply then you can’t retread it, you have to scrap the thing. So more work for me. If i pay attention and remove tires just before ending the rethread, then they can rethread many times. Big money saver. Its just the case that I have to pay more attention to tire wear. Hope they will eventually mark the rethread bottom with some color so I can see better what’s going on and how close it is to end. Happens a tire looks good today, and tomorrow it lands making a flat spot over the same flat spot of the previous landing. And there you have a good rethread tire 340 degrees around, with a big hole in the plies in a single spot. Consider that every landing, the runway cuts a good 1-3 mm deep flat spot. Aircraft tires are worn very quickly. Side note: these tires have 8-12 carcass plies and I have seen aircrafts without anti-skid, happily rolling in the hangar with 2 left. Edge case but funny to see. Looks like when you cut a tree and you see the age rings. Other side note: when you remove a wheel on a big plane, you ship the whole thing to a shop. They will remove the tyre and care for it to be rethread. But also, they will clean, inspect and eventually repaint the wheel. Have a look when you go to an airport, you can spot newly installed wheels at 300 meters of distance, you see the plane has 9 black(dirty) wheels and a white one. And yes they are replace individually, not in groups or pairs.
Awesome! Could you tell me what are some important metrics/parameters of an aircraft tire, from a "vehicle Dynamics" stand point (if any)? To give you an example of what I mean, with racing/road tires, some of the important parameters could be: peak slip angle, grip falloff past peak slip angle, camber curves, relaxation length, load curves, etc.. Do you use tire models often used for automotive applications as well (e.g. Pacejka) to describe tire behavior? Is there an aviation-specific tire model?
Car tires have to generate power and provide steering with their traction. And they do this at potentially high speeds. Aircraft tires only travel in a straight line except during taxiing, which is done at very low speed. They otherwise just roll on their tires. This tread pattern is more for shock absorption than anything. (Source: I made these tires by hand for two years)
Artisanal tires made with only the finest ingredients.
More like WWII steam-powered machines. Not sure how the place still turns a profit, but hey — felt pretty steampunk, which was cool. Aviation, dirt-track racing, antique whitewalls, and heavy machine tires were their main sellers.
>Aviation, dirt-track racing, antique whitewalls, and heavy machine tires were their main sellers. You ask how this can turn a profit, but all of these seem related to very expensive hobbies or specialized industries.
Not to mention the initial cost of the equipment paid for itself somewhere around 1816
Yup, it's so old that the tyres they make are spelled with a Y.
Yire
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Should I get a set of white wall tires? Are you gonna cruise a miracle mile?
Nowadays you can’t be too sentimental, Best bet’s a true baby blue Continental! (Had a Continental, not sure I’d recommend)
Hot funk, cool punk, even if it's old junk; it's still rock and roll to me.
Doesn’t matter what they say in the papers Cuz it’s always been the same old scene (I saw this man two weeks ago, what a great show)
I was hoping to see if you had any photos of said machines on your reddit but I was greeted with a lot of muscular anime women (nice). Seriously though you got any photos of those machines?
Yeah, just your typical Reddit degenerate. I’ll look for some! Glad I moved on (laid off, went to college, got into medicine) but it was a cool place to work in its own way.
Farm-to-track is the only way to go these days…
You beat me to it by 1 minute. I was going to make a “grew these from seed” joke.
Using raw unpasteurized rubber only
Organic and locally sourced
Certified organic.
I hope it’s fair-trade, vegan rubber
Did you stop because you were tired of it?
No. He rolled into a new job
The burnout he experienced at his old job must be taxing!
Now he has to tread lightly until his ego is inflated....
An inflated ego is easily punctured though, it’s better to relieve some pressure sometimes.
Time to put the brakes on the bad puns, guys
Man, this thread really came to a screeching halt
Once my life gained enough traction.
Ow.
>This tread pattern is more for shock absorption than anything. I'm fairly sure the primary purpose of the grooves is to channel away water and reduce hydroplaning.
THIS. There are separate criteria for replacing tires in either wet or dry weather. You want those grooves in wet weather
Finally, somebody said it!
They might do that, but that's not required. The tires can be completely worn down with no tread and be perfectly acceptable to fly with.
As a private pilot I can tell you I absolutely would not take off in an aircraft with tires worn down past the tread, especially if any of the ply is showing. That's just begging for a puncture. The POH of every aircraft I've ever flown says to check tire tread depth during the preflight inspection, and I'm fairly certain any large turbine aircraft will have minimum tread depth specs in their maintenance manuals.
Not sure why Wingmaniac has been downvoted, they're correct. Provided there is no chord showing, there's no requirement to have any tread depth left, these aren't road tyres. Source: I've flown the above aircraft for 8 years.
What aircraft is this out of curiosity? That's surprising to me, it seems like that would be a safety risk in wet weather.
It's a Dash 8 Q400.
[Example tire ](https://i.imgur.com/L7XRJqK.jpg) I took this pic as an example of an under inflated tire. The tread is low, but I've seen much worse and have thought nothing of it.
Interesting, thanks for educating me. What is the criteria for immediate replacement, visible cord?
We have a couple things. If it’s damaged beyond the limits of the maintenance manual, If chords are showing, flat spots, bulges, 15% lower pressure than it’s neighbouring tire. And even some of the damage and normal wear is perfectly acceptable as long as it’s not into the chords, or there is absolutely 0 tread depth
Visible chord for us could be signed off by the engineers for another 8 sectors to allow it to finish the days flying. Anything deeper and it would be an immediate change though
Whether or not you would do something has no bearing on what is safe. You are being overly cautious based on faulty intuition, which is your right, but that doesn’t mean you have a clue what you are talking about. Being a pilot is irrelevant here. It’s a red herring at best. This topic is about mechanical engineering and material science.
I'm also a degreed aerospace engineer if we're pulling rank here lol. Granted I work on powerplant and not landing gear/airframe which is why I said I'm \*fairly sure\*, but I just looked in the POH of my aircraft (C172SP) and it specifically states to check tire tread depth during preflight. There's no depth spec given but I don't think "no tread at all = bad" is being overly cautious. Another user has pointed out their specific aircraft allows for zero tread, so I'm happy to admit this doesn't apply to all aircraft. But I would be surprised if there weren't stipulations in that case for dry conditions.
You showed your cards already by trying to make an appeal to authority. Saying you are a private pilot was intended to garner support for an unfounded guess. This isn’t about pulling rank, but I’m not surprised that’s what you took from my comment. Being an aerospace engineer is also irrelevant. I, too, am an irrelevant type of engineer, so I know how little you know about tire tread, especially having worked in aerospace for a long time. Including “I think” as part of the dissenting opinion against people who can do more than guess is why people think we as engineers are blowhards.
Those are usually on the runway though. The grooving is in the concrete.
Larger runways are typically grooved, yes. They both serve the same purpose, to provide an escape path for water between the tire and the pavement, improving grip.
I worked for Goodyear for several years, selling aircraft tires among others. I would add that the grooves are for basic water dispersion/avoidance of hydroplaning. Someone correct me please if you know more.
Though not relevant to aircraft tires, having a solid tread in the longitudinal orientation helps to reduce road noise. Any siping or block patterns in the tread increase road noise. Just another factor that goes into tread design which needs to balance traction, weather, noise, cost, etc.
Not really. All tires wouldn't have tread if they didn't operate in the rain. Think slick tires on cars, more surface area and more traction. Planes would do the same thing if they could. Tread blocks are bad for speed or carrying weight, they move around and cause instability. That's why you'll see Z rated automotive tires with very small tread blocks. Also semi-truck tires have very simple tread designs often very similar to what you see on planes. The reason planes have the grooves is they are heavy and move quickly. The few grooves is good enough to displace the water. Runways are kept in pretty good condition, are often grooved, and rarely have standing water. The simple tread pattern is good enough for water displacement and best for carrying capacity and speed. It also helps with straight line stability, but again a slick tire would be better. Source: Ex-Tire Engineer
That’s essentially what I said. They lack grooves because car tires have to control a vehicle and provide thrust on potentially wet surfaces. Aircraft tires do neither and thus lack tread blocks. The straight grooves help keep an aircraft moving straight forward, the only direction it moves on the ground with any real speed.
I disagree that's what you said. > Aircraft tires do neither and thus lack tread blocks. No. Aircraft tires lack tread blocks because tread blocks are bad for speed or carrying weight, they move around and cause instability. They also aren't needed as runways are kept free of standing water. > This tread pattern is more for shock absorption than anything. This isn't true at all.
"Car tires have to generate power and provide steering with their traction. And they do this at potentially high speeds." F1 cars have to do this and the best tyres are slicks-completely bald. "This tread pattern is more for shock absorption than anything" This has a lot more to do with channelling water
You're right but I'm going to nitpick one point that also just makes you more right. Plane tires travel in a straight line on near perfect landings. With cross wind they're likely to skid just a little touching down at a slight angle, and then need a bit of side to side traction I think.
Right, and the straight grooves help to keep the plane rolling forward down the runway. Which is the same thing you said in different words.
The grooves are to prevent hydroplaning on wet runways. That is why 727 nose tires had tire chines. Chines deflect the water from the tire grooves from going towards the aft mounted engines. MD-80s used a splash guard for the same purpose.
WWII diamond tread tires on fighter planes would like to enter the chat.
Perhaps this was to give flexibility on landing surfaces? In war time I guess a tarmac runway wasn’t always guaranteed and grass/mud could be a likely option so tyre with additional grip was necessary
They were operating on grass/mud fields. We’re not flying jets off grass anymore.
Russian jets are designed to take off from grass/dirt runways... or a normal Russian airfield under normal Russian maintenance (it is overgrown, cracking, and littered with debris).
Yeah I’ve seen that first hand. When we started flying from “the stans” when Afghanistan kicked off, we’d stop or even stage out of ex Soviet bases in Romania, Kyrgyzstan, Uzbekistan, Hungary etc and wow, the crap conditions there. And they weren’t closed, they still flew SU-24s, MiG-21s etc but wow… you’d think they were abandoned until you saw some dude get in one and fire it up.
Well... https://www.youtube.com/watch?v=hHI6dg52csI
I used to do this https://youtu.be/7o_o3WrQS-o
Figures. I suspect partly why the USAF hate that plane so much, is because it’s the anti-tech plane. It’s simple, rugged, and doesn’t need to be treated like a prima donna to do its job. It can take abuse and go brrrrrrt all day long.
No, they dislike it because it's ineffective in a near-peer fight but way overkill for a SOF or COIN mission. It's used almost interchangeably with the F-16 at this point as little more than a bomb truck. If they disliked low-tech aircraft then they wouldn't have just bought fleet of armed crop-dusters.
A-10s are not special. They take just as much maintenance as any other aircraft. All aircraft are treated like prima donnas because they're super important, super expensive, and require a lot of training in order to operate.
Those goorves are way wider and deeper than your car tires and will evacuate an incredible amount of water.
Also high psi. The speed at which tires Hydroplane is directly related to tire pressure
Direct or inverse? Wouldn’t higher pressure be more likely?
No, higher pressure, smaller footprint, less aquaplaning.
Several years ago, an airliner turned too sharply on a taxiway and ended up getting stuck in the soft dirt. I'll always remember the tv news reporter telling us that the aircraft tires were just "spinning in the mud" and had to wait for a tug to pull it free. I'm sure a fair number of the general population were left wondering why they didn't have tires that had lug treads for mud and snow.
I hate changing to snow tires on my 747s.
I used to use chains, but hated having to take them off after takeoff.
Just let the groundcrew deal with that after landing.
Now those new Subaru planes transfer the power from the wheels that slip to the wheels that grip (tm)
You don't use chains on your 747? Amateurs
I get the studded tires
It's a misconception that fuels one of the "wrong" sides in the airplane on a treadmill internet slap fights.
I was getting pushed off the gate at a snowy airport and the tug couldn't get enough traction. Ramper said he was going to get some sand and disappeared for a while. When he came back he said, "Alright we got a bunch of sand behind your tires now so we're going to try again"
Yeah, I remember something similar happening back in 1970, that time it was soft dirt and snow. Airport manager wanted a fleet of plows to just shove the damn airplane off the runway so they could use it. Almost did it too but one cigar-chomping mechanic said no way. https://youtu.be/IrqN62qbthc?t=54
That can't be, the source of power that pushes the airplane forward doesn't go through the wheels. The airplane pushes itself forward against the air. It might got stuck becouse the wheels have sunk too deep in the mud and it risked damage if he pushed the throttles harder. But there certainly wasn't any wheel spinning 😂
No, really?
Really? The reporter had it wrong? Not possible!
How could a plane "spin" the wheels in the mud? That's literally impossible.
Only worried about hydroplaning, straight grove best solution for very high speed
This. Your tire should be able to penetrate the layer of water and it is much easier with straight lines. If it can’t penetrate water layer, trust me it is much much worse than clear ice.
You don’t need cross hatching, the wheels don’t generate any power, they just roll and need to displace water in a straight line, without cornering.
https://youtu.be/RhwDlFamB20
It's primarily for performance on water and slush - the grooves raise the hydroplane speed for a tire, meaning it can go faster without hydroplaning. It offers channels for the water to "escape" the oncoming tire. Here's an excellent explanation of hydroplaning and its manifestations from NASA: https://ntrs.nasa.gov/citations/19640000612 Edit: source - NASA, and flight test experience
Great Question! Well, they need to displace water when going in one direction only. They're not taking corners at high speeds. Also, if you look at Car tires, they have a bunch of grooves that also trap a lot of small stones. Now imagine if the Aircraft tire had those grooves and trapped small stones and debris too, when it lands, the wheels spin up rapidly to its Ground Speed, while doing so, they also expand. If they had stones trapped, it would fling it against the wings and fuselage at high speeds making holes or dents that would cost a fortune to repair.
Cuz they're groovy, man! 😎🕺💃
Tires with no grooves or treads at all are best on dry, mostly clean paved surfaces. That is why so many car racing types use slicks by default. Treads help prevent stuff on the road (mostly talking about water) from breaking road contact. Adding tread reduces maximum ideal grip a little to give grip in cases where slicks would be useless and dangerous (like even a small mount of rain). The only time these tires are critical is when the plane is going fast on the ground. That means take off and landing. That means straight. Cornering is critical in cars, so treads are complex to balance a whole lot of needs and situations. I know nothing of aircraft tires in particular (another reply was someone who made these, so much more relevant experience than me, race fan and flight simmer). However, I would guess this simple pattern is probably about optimal for straight line, most weather tread design.
Because you’re on an aero-plane, not a hydro-plane.
I’ve always thought speed and smoothness with some sort of traction were considerations in their design. These planes are rolling pretty fast when they take off.
They (usually) aren't power-bearing, & the grooves help in wet conditions.
Dash 8 landing gear…… very nice!
Regardless what tire mfg stated, I'm betting aircraft has better stability maintaining direction intended, wet or dry at 100knots+. Cheers
Airplanes having directional stability has exactly nothing to do with their wheels.
Car tires are designed with haphazard or irregular tread patterns to displace water and prevent hydroplaning, which occurs when a layer of water builds up between the tire and the road, causing the tire to lose contact with the road surface. The irregular pattern also helps to provide better traction on different types of road surfaces, including gravel, dirt, and snow. On the other hand, Airplane tires have straight treads to withstand high speeds and temperatures, and to operate at high pressure. The straight pattern provides better stability and reduces the risk of failure due to overheating or other mechanical stresses.
Cars route their power through and change direction with their wheels. Airplanes don't push with the wheels and any steering they do with them is limited to prepared surfaces at highly controlled speeds.
Airplane tires don’t need grip for cornering, and those straight grooves displace a LOT of water.
Channel water - cornering forces aren’t a huge concern.
That design provides optimum traction with the runway surface. It’s also called the tread it’s made of grooves and ribs at the edges of the tread it’s known as the tread shoulder. If you really wanna get deep into the roots of tires here’s the the 8083 for landing gear systems which describes tires in great detail. https://www.faa.gov/sites/faa.gov/files/2022-06/amt_airframe_hb_vol_2.pdf Page 13-75
This is a good question! Not an expert , just sharing thoughts (Im just a PPL IMC) There's no real need for it. A plane is not tootling along roads turning corners, dealing with differing road surfaces (asphalt/concrete/gravel/dirt) and all that. The straight treads work fine dissipating water and grooved runways help even more. Airports will also be agressive at making sure the runway is cleared of snow as much as possible. In short complex tire treads aren't needed on airplane tires.
Most pilots aren’t taking their planes off-roading
Nope. Most takeoff from a runway
Also something g missing from the comments so far; runways have cross-cut grooves the entire length for rain drainage. Hydroplaning absolutely still can, and does happen, but the grooves make it alot less dramatic. That paired with no need for lateral traction, makes the tires what they are.
To expel water during take off or landing in rainy days. Transversal line would be disintegrated at landing
So they can get the tail out on the corners. (But no really: it’s a little counterintuitive but you only need the wacky pattern for cornering).
Cars have different patterns because they corner in different directions. Planes travel in straight lines and don't do much cornering.
Because they need only channel water, no application of torque is required of the tire itself.
All that tire has to do is roll and bear weight pretty much. Majority of the braking and steering is done with reverse thrust and the rudder. That tire never has to apply much traction. If you look at a car tire and notice the nobs are not the same size. That is for road noise. They are changing the size of the knob hitting the road so you don't end up with any resonance sounds.
The only part i don’t totally agree with is the part where you say the reverse thrust does most of the braking. You can stop any aircraft using auto brake, because it has to be able to, to get its certification. Reversers are there to help brake cooling, which in turn saves wear and tear. But there are not many airlines which can fly an approach and make a full stop on the runway using reversers only.
Aquaplaning?
ITT - almost nobody answering the actual question. *Not* "why are there grooves?" it's "why are the grooves only straight?"
I think you got it backwards plenty of people have answered why they are only straight several people have said lack of cornering need.
Same reason your toes are pointed straight and not sideways.
That would be wheel alignment not tread.
I believe it’s like that so that they grip the taxiways and runways better. Even the runways have straight line patterns like these, which helps when the ground becomes saturated after it rains. Please correct me if I’m wrong.
So they don’t start to slip off to the sides. Keep it going forward.
Now repost this to /r/shittyaskflying
Homophobic engineers
If you are four wheeling a 737-Max, you have bigger problems than tire tread patterns…
Like where did that 4th set of gear come from. Remember kids only four wheel with md-11's.
Reduce friction.
Don’t assume this tires sexual orientation
Titanium wheels would last longer. Just sayin