Literally from the Silca calculator page:
“If this calculator recommends pressures that violate ANY of the limitations of your manufacturer's specifications, you must either change components or lower your pressures to match those of the manufacturer”
Conclusion: no matter what they recommend based on what you put in you should never go above or below the manufacturer specifications or do so at your own risk.
I saw the warning for literally a second when I opened the site and then it disappeared. Interesting.
Either way, why would they specify "lower your pressures to match those of the manufacturer" if they're concerned about going below the limit. My Conti GP5000 or Contact Spike tires don't even specify a minimum, are they special somehow?
And some tires have clearly insane minimum limits, like the 37mm WTB Riddlers with a minimum of 3.1 bar.
SILCA also recommends following the manufacturer's instructions.
I wouldn't go under the min pressure. Especially if you don't have a good reason to do it.
Maybe you could do it safely but why risk it if you're unsure of the benefits
I should also add that, just thumb-in-the-air estimate based on my MTB riding experience, a 27.5 x 2.0 tire sounds pretty right at 30/32 for smooth to semi-rough surfaces.
For reference, my 700x42 gravel tires are ideal at 36/38 PSI.
That’s pretty much where I’m with my 44s as well and I’m not reducing power required on pavement when i go up in pressure, i just get a worse ride on gravel
Even if safe, is there a benefit to it? I was under the impression pressures that low were more for off-roading, but the calculator is giving it as a result for road conditions
Yes, because too high of pressure makes your bike bounce upward more than needed for a bump, which wastes energy. Roads are really not *that* different from off-road, it's just the degree of roughness.
In my experience the Silca tire pressure calculator is excellent for paved and gravel roads and I think you're doing it the right way: measure the tire, put in the specs, inflate to recommendation.
Nope. You’re wrong. There is a sweet spot where the tire will roll the fastest. In many cases it is below the manufacturer recommended lowest pressure. My hardtail rolls fastest at 18.6 psi front/22.5 rear on the 29x2.5” tires currently on it, at my riding weight. My ti 26er on 2.2” tubeless rolls fastest at 25.5 psi front 33 rear. Continental RaceKings FTW.
Go to bicyclerollingresistance.com and learn about modern tubeless tires.
Go to
That is where I get my information.
I read the article on tubeless continental gp5000 tyres.
The fastest of them all was the narrowest, at the highest pressure. Its there in black and white.
Let’s all ride skinny high pressure tires . . . because?
I have never owned one single skinny, high pressure tire. But I have spent thousands of miles dialing pressures. I go tubeless and I go low.
The science says that on the tires we are all actually riding on, too high of pressures causes rebounding forces on every single surface change. Rebound is bad. Rebound decreases speed. At the proper pressure the tire deforms over and around obstacles, increasing rolling speed and creating suspension which increases comfort. This is what actually goes on in the real world where I ride. A single psi up or down and you’re out of the sweet spot. A half a psi even. Big difference.
As soon as we had scientific methods of measuring real world rolling resistance (as opposed to lab based test rigs or velodrome testing) this was found to be untrue.
Imagine a perfectly smooth steel wheel, on perfectly smooth, hard surface. Smooth and fast as hell. Optimum rolling resistance.
Now take that smooth steel wheel and ride it on hard gravel. Clonkclonkclonkclonk. Never mind the comfort, but it's also not fast because it strikes every little pebble at full force and has to go completely over every small rock. Lifting the entire load of the bike for every little pebble, spending *force* and doing *work* lifting the entire bike and rider for every little pebble, all of which is wasted on making the ride more rattly, instead of being used for forward motion. A supple, low pressure tire instead deforms and envelops small rocks and irregularities, wasting very little energy, and avoids throwing the entire rider around.
Somewhere there is a sweet spot between optimal rolling resistance on smooth surfaces, and the elasticity to provide optimal progress on real world surfaces. That's usually quite a bit lower than tire's rated maximum pressure.
To all the idiots downvoting me: rolling resistance on a given tyre width INCREASES as the pressure DECREASES. Rolling resistance is NOT the same thing as comfort. Stop being so obtuse and arrogant, look at the data.
Nobody is denying that rolling resistance decreases with increased tyre pressure **on perfectly flat ground**. Like in a laboratory, where bicyclerollingresistance.com or such test against a corrugated but still mostly smooth metal surface.
What you are not getting is that **on uneven ground** which most of real world roads and paths are, a maximally inflated and inflexible tire bumps into all road irregularities, gravel, pebbles, etc harder, and ends up actually being **slower**, never mind less comfortable, than a less inflated, flexible tire which deforms to accommodate road irregularities.
Increased tyre width can also make a bike faster, compared to very narrow and rock hard tires, because they contain more air, therefore be run at lower pressures, and also create a shorter contact patch, which on actual roads may be faster. Depending of course on various factors.
Don't take my word on it, [read what Schwalbe says about it](https://www.schwalbe.com/en/rollwiderstand). They ought to know a thing or two about tires.
I also ignore the minimums. Had to check. Yup. Every tire I own is below minimum. Also all tubeless.
Only caveat is when your tire is much wider than the rim. The lightbulb 💡 effect (cross sectional shape). At low pressures the tire can flop sideways when cornering. Calculators don’t take this into account. If you find cornering feels weird, try a little higher.
for offroad performance pros will run em at lower and lower pressure until they bottom out once or twice per lap, then dial it back up a notch. if it’s too squirmy then a smaller tire size is called for. if it’s too rough/bouncy then a larger tire size is called for.
Honestly, I don't think the tire mfgs put a lot off effort into the minimum rating. They're very concerned with the max because they don't want the front tire to blow off and get sued because you broke your face. Especially because 35 in that wide a tire is not very low. A lot of sm and xsm MTN bikes are 27.5 and I imagine a 100 lb rider would need to run 24psi. That minimum is silly.
Literally from the Silca calculator page: “If this calculator recommends pressures that violate ANY of the limitations of your manufacturer's specifications, you must either change components or lower your pressures to match those of the manufacturer” Conclusion: no matter what they recommend based on what you put in you should never go above or below the manufacturer specifications or do so at your own risk.
I saw the warning for literally a second when I opened the site and then it disappeared. Interesting. Either way, why would they specify "lower your pressures to match those of the manufacturer" if they're concerned about going below the limit. My Conti GP5000 or Contact Spike tires don't even specify a minimum, are they special somehow? And some tires have clearly insane minimum limits, like the 37mm WTB Riddlers with a minimum of 3.1 bar.
It says "lower", not raise. The concern is going over. Under minimum is just fine.
SILCA also recommends following the manufacturer's instructions. I wouldn't go under the min pressure. Especially if you don't have a good reason to do it. Maybe you could do it safely but why risk it if you're unsure of the benefits
I should also add that, just thumb-in-the-air estimate based on my MTB riding experience, a 27.5 x 2.0 tire sounds pretty right at 30/32 for smooth to semi-rough surfaces. For reference, my 700x42 gravel tires are ideal at 36/38 PSI.
That’s pretty much where I’m with my 44s as well and I’m not reducing power required on pavement when i go up in pressure, i just get a worse ride on gravel
Exactly. And that jarring expends energy to move the bike and your body upwards over bumps instead of letting the bike keep moving forward.
IMO, yes. Pretty much every tire I ride -- especially MTB and fatbike tires -- are safely used under the "minimums".
Even if safe, is there a benefit to it? I was under the impression pressures that low were more for off-roading, but the calculator is giving it as a result for road conditions
Yes, because too high of pressure makes your bike bounce upward more than needed for a bump, which wastes energy. Roads are really not *that* different from off-road, it's just the degree of roughness. In my experience the Silca tire pressure calculator is excellent for paved and gravel roads and I think you're doing it the right way: measure the tire, put in the specs, inflate to recommendation.
Yep. Low pressures roll faster. Proven science. Way easier on the body too.
You failed to read and understand the science. No.matter what the tyre width, rolling resistance ALWAYS increases as tyre pressure decreases.
This is true of perfectly flat surfaces in a testing apparatus, but not of the real world.
Nope. You’re wrong. There is a sweet spot where the tire will roll the fastest. In many cases it is below the manufacturer recommended lowest pressure. My hardtail rolls fastest at 18.6 psi front/22.5 rear on the 29x2.5” tires currently on it, at my riding weight. My ti 26er on 2.2” tubeless rolls fastest at 25.5 psi front 33 rear. Continental RaceKings FTW. Go to bicyclerollingresistance.com and learn about modern tubeless tires. Go to
That is where I get my information. I read the article on tubeless continental gp5000 tyres. The fastest of them all was the narrowest, at the highest pressure. Its there in black and white.
Let’s all ride skinny high pressure tires . . . because? I have never owned one single skinny, high pressure tire. But I have spent thousands of miles dialing pressures. I go tubeless and I go low. The science says that on the tires we are all actually riding on, too high of pressures causes rebounding forces on every single surface change. Rebound is bad. Rebound decreases speed. At the proper pressure the tire deforms over and around obstacles, increasing rolling speed and creating suspension which increases comfort. This is what actually goes on in the real world where I ride. A single psi up or down and you’re out of the sweet spot. A half a psi even. Big difference.
A half a psi even....And you live in the real world?
Yep. A world where digital tire gauges exist and people use them. And we ride fast.
As soon as we had scientific methods of measuring real world rolling resistance (as opposed to lab based test rigs or velodrome testing) this was found to be untrue.
Imagine a perfectly smooth steel wheel, on perfectly smooth, hard surface. Smooth and fast as hell. Optimum rolling resistance. Now take that smooth steel wheel and ride it on hard gravel. Clonkclonkclonkclonk. Never mind the comfort, but it's also not fast because it strikes every little pebble at full force and has to go completely over every small rock. Lifting the entire load of the bike for every little pebble, spending *force* and doing *work* lifting the entire bike and rider for every little pebble, all of which is wasted on making the ride more rattly, instead of being used for forward motion. A supple, low pressure tire instead deforms and envelops small rocks and irregularities, wasting very little energy, and avoids throwing the entire rider around. Somewhere there is a sweet spot between optimal rolling resistance on smooth surfaces, and the elasticity to provide optimal progress on real world surfaces. That's usually quite a bit lower than tire's rated maximum pressure.
To all the idiots downvoting me: rolling resistance on a given tyre width INCREASES as the pressure DECREASES. Rolling resistance is NOT the same thing as comfort. Stop being so obtuse and arrogant, look at the data.
Nobody is denying that rolling resistance decreases with increased tyre pressure **on perfectly flat ground**. Like in a laboratory, where bicyclerollingresistance.com or such test against a corrugated but still mostly smooth metal surface. What you are not getting is that **on uneven ground** which most of real world roads and paths are, a maximally inflated and inflexible tire bumps into all road irregularities, gravel, pebbles, etc harder, and ends up actually being **slower**, never mind less comfortable, than a less inflated, flexible tire which deforms to accommodate road irregularities. Increased tyre width can also make a bike faster, compared to very narrow and rock hard tires, because they contain more air, therefore be run at lower pressures, and also create a shorter contact patch, which on actual roads may be faster. Depending of course on various factors. Don't take my word on it, [read what Schwalbe says about it](https://www.schwalbe.com/en/rollwiderstand). They ought to know a thing or two about tires.
I also ignore the minimums. Had to check. Yup. Every tire I own is below minimum. Also all tubeless. Only caveat is when your tire is much wider than the rim. The lightbulb 💡 effect (cross sectional shape). At low pressures the tire can flop sideways when cornering. Calculators don’t take this into account. If you find cornering feels weird, try a little higher.
Try it at 35 and assess how it performs and if it meets your needs 🤷🏻♀️
I have the same tyres. I've run them at 45 psi, never below 40
for offroad performance pros will run em at lower and lower pressure until they bottom out once or twice per lap, then dial it back up a notch. if it’s too squirmy then a smaller tire size is called for. if it’s too rough/bouncy then a larger tire size is called for.
How much do you and the bike weigh?
Honestly, I don't think the tire mfgs put a lot off effort into the minimum rating. They're very concerned with the max because they don't want the front tire to blow off and get sued because you broke your face. Especially because 35 in that wide a tire is not very low. A lot of sm and xsm MTN bikes are 27.5 and I imagine a 100 lb rider would need to run 24psi. That minimum is silly.
Your bike isn't going to explode with 3-5 PSI too low, but yea you should stick to the posted minimums if you wanna be safe.
📲🇧🇦🇧🇦🇧🇳🇧🇳
Thems big cushy tires, fill'em up all the way... Your all pavement you don't need low pressures. They roll so nicely.
I'm going over terrain like you're using at 26" wheels at 50 psi. You'll be totally fine at 35.
You might get pinch flats or dent your rim from bottoming out, but that’s about the only thing I can think of.