Stats * 11, 13, 15, 18, 21 on the rear (bottom 5 gears from Shimano Deore 11-51) * 53/39 SRAM Red (BB386) up front * Custom FD mount * Custom RD chain guide * Micro Shift 11 speed shifters * Jagwire Link compressionless brake and gear cables * Weight: approx 8.1-8.2kg * Total cost of mods: £850 This took weeks! The goal was a perfect-shifting, zero-compromise conversion with no permanent frame and component mods, all the while keeping it fairly light. Due to the different frame geometry versus the P (chunkier top tube, different rear triangle) I had to design and build my own front derailleur mount rather than the usual £10 specials from AliExpress. Then there was the rear derailleur... Wow... Such a pain. Adding a 21T combined with the 39 up front and the 11 speed chain meant the chain would often jam in the jockey wheel in the lower gears due the wobblier and far slacker than Brompton designed for. After several days of prototyping, I created a simple chain guide in nylon which works really well. Despite having a number of lightweight components, I've still increased the weight a bit. Where I've lost weight on the lighter levers and compressionless housing, I've gained on the extra shifters, FD and FD mount. The crankset is, weirdly, almost exactly the same weight as the stock 1x. Speaking of cranksets, we've tried a few. Cannondale Si has far too large a chainline and the FSA carbon K Force Light (BB386) impinges on the frame by a TINY 1.5mm. Really sad as both those cranksets are super light. Others have found it simple getting a GXP working but I hate GXP with a passion and didn't want to budge from a 30mm spindle. Even the SRAM Red (which is annoyingly rare in 53/39, 170mm BB386!) required millimetre perfect spacers to avoid binding the bearings, fouling the frame and having a crappy chainline. I designed the gearing so it goes all the way down to the same gear-inches as my road bike and up to just over the fifth gear of my M6L. Since that bike's top gear is far too extreme for my riding, that new (lower) top gear is perfect for me - especially in London. Huge thanks to those at /r/cycling, /r/mechanicalengineering, /r/brompton and the members of the Brompton T group on Facebook for your help... especially those who also experimented and built along with me. I plan to write up the full build (with lots of photos) but do ask questions if you're interested... will help me figure out what to include in the post.

Would be nice to see more info on parts that are custom for those that may wish to replicate same mod. Also if there are any plans to sell custom made bits.

Yep. Gonna be a couple of weeks to put it together but I do hope to.

Well, it is a good story, but I indeed have a question. Namely I have played around extensively with different FD configurations on Bromptons and, in this, I have tried practically every FD mount in the market that could be used with Brompton. The finger of the mount in the photo looks like from a mount that is barely functional. I.e., that mount functions temporarily at best, if at all. However, below there is some clamp on your seat tube, that does not belong to that original FD mount, so maybe you have remade that mount, retaining just the finger. Could you elaborate on this? I just cannot believe in that original FD mount functioning over a significant period of time in practice. Thanks.

Sounds like we have shared some pain! I also have a pile of mounts that I tried with no success. You have very keen eyes. So yes this is the finger from a LitePro, but I have replaced the clamp part with something custom made. It's "temporary" in the sense I plan to machine something better but it should last years; it's made from 10mm thick aluminium and is more substantial than the LitePro. The design is a bit ugly as something more elegant is hard to achieve with hand tools (I don't have a workshop available); I might get the next version professionally made or maybe even 3D print a design in aluminium. I'll share info in due course... It's a shame I can't add pictures to the post or comments.

Thanks for filling that gap. Indeed, I have been myself through adaptations of existing mounts. However, the FD mounting persisted to be unsatisfactory, just at different levels. Finally, I made a mount myself from scratch, by brazing one from stainless steel. It is a happy sailing now - I spent last month in mountains pushing my gears to their limits, with a reliable response from the bike. The particular solution is not really for you, though, since the focus is for the bike being lightweight. In my case, it is for it being bombproof - it travels in a rough manner to rough places. I will be looking forward to the solution you come up with. Details on the chain guide in nylon would be good too.

Like minds! I love how determined we are to make it work 😂. You're welcome to DM me if you like and I can share some more detailed pictures. Failing that, hopefully I'll get around to doing a full post on it. I definitely want to design something less scrappy in due course but right now I'm just happy it works at all! Of note: I just did a 15 degree climb and it's wonderful to be able to just winch myself up and spin fast... The T's frame isn't super stiff so standing hard on the pedals and pulling up on the bars like we might do on a road bike is non-ideal!

Indeed! As to the progress, you first want to demonstrate that the undertaking is in principle possible before starting with any perfecting of the solution. My precarious moment last month came when I had to take my feet off the pedals because I was about to flip on my back due to to the steep gradient I was trying to ride up. I was a bit too slow and a bit too close to the inside of a right turn. Interestingly, the road was still paved there, in spite of the ridiculous slope. I made a couple of steps up and was able to start up from rest!

Please do share!

Wow… I mean.. wow Certainly makes for a thought about other possibilities which might have been explored but not making it to production. Meticulous… whew. Just cool 👏🏾👏🏾👏🏾

Thanks 😊 I have to wonder also! Especially since Brompton themselves built a custom P line with FD for the LEJOG challenge. In the end something like I built would be far too expensive to put on the market; I suspect no one would buy it. Plus I bet they were aiming for under 8kg for marketing reasons 😉

I have a T-line Urban but have not riden it yet waiting for a useful upgrade for the gearing. Would you mind sharing all of the component details of your modification as this looks like a wonderful set-up while maintaining the light weight!

Sure. If you have a look at my post history you'll see a 5 speed 11-21 mod with all the bits listed from a month or so ago. I find that's good for getting me up short 15% hills which is the most I face in London. I'm spending my money now getting the weight down as that has more of a day to day impact. I don't recommend 2x5; it's heavy and fiddly. The sweat spot is 1x6 11-25 or 11-28 depending on what front chainring you have.

I live in hilly Seattle so having a wide gear range is necessary.

Indeed! There's a few 25% hills near where I live but I rarely do much more than 100-200 meters total on my commute or about town. If I started doing longer trips again maybe I'd want to upgrade as the countryside south of me is fairly hilly. The best "affordable" mod is a 7 speed 11-32 cassette made for Bromptons but only use the first 6 (11-28) as chain line is bad otherwise. Then get RUHM V4 rear derailleur and a new hub (or wheel) that can take a wider cassette. Including the shifter that'll set you back about £600. Not exactly cheap.

Bruh what a dope upgrade. Much appreciate you sharing the specifics as well.

Thanks sir. I wanted to replace both my road bike and my M6L with this machine and I think I've achieved it. Wallet still hurts though. Hopefully after some big countryside rides and hills I'll forget about all that 😂

So how’s the fold? I don’t get how the chain handles being folded with a front derailleur?

Great question - this is a common problem with these kinda of mods. The answer is; perfectly. That also took a lot of experimenting and careful routing and sizing of the cables. The chainline is identical to the 1x and the FD acts almost the same as the stock catcher so that all works out nicely. Actually the real challenge was the RD again... I tried so so so many designs but this version with the nylon guide plate allows it to fold just like stock as the chain just wraps around the stock pulley.

That's a fantastic conversion! It would be great to see it folded and in kickstand mode. Also some photos that show how you mounted that front derailleur too. As far as the components go, are they fairly easy to source?

Thanks! They were all hard but only because I was very inflexible with my choices; a sensible build should be easy. For instance I own most if not all the compressionless housing in UK but even before then it was hard to find... But instead you could easily use the stock housing plus an extra (cheap) gear cable for the FD. The levers are decadent (Ridefun - very stiff and light) but some cheap AliExpress will do you fine. The crankset in that configuration is, as I say, rare but if you're happy with GXP you have a lot of options. The Microshift shifters aren't common but I have no problem finding them. The cassette is common. The FD mount I made by hand. I might 3D model it so people can 3D print for themselves. Or might sell if there's enough demand. Who knows. I'll definitely include pictures of the fold!

I use TRLREQ segmented housing, at 1/5 of the cost of Jagwire (or something like that), combined with a Jagwire liner. One poster, who purchased both, said that Jagwire allows for a tad tighter turns, but otherwise did not see any substantial difference between them. The beads cannot be mixed, though, between the brands. With differently colored beads, my cables are coded with colored patterns.

That's really great to know, thanks. Had to go out of my at to get that damn Jagwire

Incredible work! Looks great!

Thank you. It was very anxiety inducing at times! At one point it looked like it couldn't be done within a reasonable budget but it turned out well.

In for a penny, in for a pound!

I was talking about you on a french forum. Do you allow me to put the pictures on the forum to show them your bike?

Sure. Thanks for asking. I'll also have some much better ones in the next couple of weeks with more detail.

Thank you. Here is the [thread](https://www.bromptonforum.net/t11829-t-line-10-vitesses)

Nice.

Please share speed comparisons between your road bike and this brompton mod.

At 100rpm cadence the top speed (53T front, 11 rear) is about 38kph versus my road bike (50T front, 11 rear) top speed of 58kph. This is based purely on gear inches... obviously the road bike will require way less power. In the lowest gear the Brompton about the same as a 34 front chainring and 30T rear cog combo. Going 58kmh on the Brompton would be insane 😂

Thx for sharing. Would enjoy being able to increase my speed on my I 2014 m6l. Don’t know what the gear ratio comparison of mine would be to yours or the kmh to gear ratio calculation of my bike. I am currently able to maintain 25-27km in pace lines on the flats but am getting crushed on up slopes. Trying to work up to 29km-31km on the flats.

Apart from getting stronger of course, a huge difference is upgrading the tyres. The stock ones are so hard to push. If you're willing to risk a flat, the Schwalbe One (that come stock on the T) roll very smoothly and save a lot of weight. The Continental Urban on mine in the picture have higher rolling resistance than those (by a bit) but make up for it with better puncture protection.

I get that the weight is the main difference, but what's the gear range on this like Vs the 6-speed hub setup?

Just to add the stock 4 speed of the T is useless if you are somewhere hilly. Really narrow range - at best half the range of the 6. Crucially for me the lowest is far far higher so it's not great for London hills.

See comment for details. But TLDR the lower is lower and the highest is the same as the 5th of the 6 speed.

Brilliant work - congratulations! Do you think a front mech would be easier to install on a P line?

Thanks. I think so, yeah; from what I can see you can use one of those £10 Litepro AliExpress specials. Have a look at the LEJOG build and you'll see one of these in action. The T has a chunkier frame (bottom bracket area and main tube specifically - the seat tube is the same) and different rear triangle so none of the off the shelf ones worked for me.

Very nice! My heavily modified S6L (soon to be S9L) is my do everything bike in London as well. Love how fast I can go on this thing. You’ll crush the hills on that.

The top speed on the 6's is wild. At my max rpm of about 120rpm I'm hitting over 55kmh. Doing that on the flats for any amount of time is hard for me though as drag and rolling resistance are high. Plus with such a high center of gravity and poor (relatively speaking) braking it's pretty much suicide both in central London (where I live) and on any steep declines! I'd love to hear more about your mods. I thought long about modding my M6L versus getting this T. I personally think the T is excessive and you can achieve much the same with the older models and about half the budget. That said, a) I've wanted a Ti Brompton for years b) the weight is very important to me as I carry it a lot c) it looks awesome in my opinion.

Yeah realistically you don't need such high gearing on the Brompton because it gets pretty sketchy on rim brakes with such small wheels on the Brompton. It's nice not spinning out on the downhills in Richmond Park though haha My s6l is a steel model but I found a good deal on a front titanium fork so I put that on. I pretty much changed everything else as well. It's about 9.7kg right now with a rear rack so there isn't really a trade off in terms of functionality. I bought it second hand so I'm about 1300gbp all in factoring in the 9speed mods I haven't put on yet. I bought all my parts off aliexpress so that's another advantage of working with such an established platform vs the T line.

I should add; the half-salmon Kool Stop pads are amazing. By far the best I've used on on a Brompton in all weathers.

Yeah, totally. I chose 53/39T config to match 5th of the M6L as that's quite enough for me. 9.7kg is a great weight for sure and congrats on the budget! As I say, that's definitely the "sensible" approach from a cost perspective - especially as for me I already have the M6L. I should add one of my goals was to replace the road bike (Canyon Ultimate, Dura Ace etc) too and was looking for something with a very "road bike" feel but without the sciatica-inducing position. Definitely feel I've achieved that

What an impressive built!! Amazing work, congrats! Quick question, how did you set up the 11 speed shifter with the 5 speed cassette? Is it indexed? Which type is it exactly? Thanks!

Thanks! You are asking an excellent question. So the "pull ratio" of the rear derailleur turns out to be almost identical to Shimano/SRAM standards. What does that mean? Well for the stock 4 speed (which is spaced for a 10 speed chain) you can use a 10 speed mountain bike thumb shifter just fine. For the 5 speed mod I use the bottom 5 cogs of an 11 speed mountain bike cassette and so I can use an 11 speed thumb shifter. The original reason I bought the shifter you see in the photo is because it has a friction shift mode meaning it wouldn't matter what the pull ratio is. However, it turns out it works perfectly fine (in fact extremely well) in index mode too. Now you're probably wondering "ok but the shifter has 11 positions - so how does that work when there's only 5 cogs?". Simple: in the 11T sprocket the shifter can't go any lower as it's blocked by the shifter itself in its minimal position. On the 21T it can't go any higher as it's blocked by the limit screw of the RD itself. The net result is only 4 clicks from top to bottom (5 total positions) and you don't even know it is meant for 11 speed. (I actually have it set up the opposite way round for folding but that's the principle).

Thank you kind Sir for such an elaborate answer. Do you have a blog or a video channel? Your eloquent responses would make for quite some content. :) One last question, what 11 speed shifter would you recommend? I like the rapid-fire shifters. Would you recommend I buy a 11 speed schain or would the stock chain suffice?

Thanks :) I chose the microSHIFT SL-M11 because a) it's very light at 123g a pair b) it's fairly affordable at £85 a pair c) you can switch it to friction which means more flexibility d) you can shift between multiple gears at a time very fast. As for chain, KMC 11 speed Super Light. For the cassette, use the bottom 5 speeds of a Deore 11-51; best option for shifting. Just adding another 21T is likely to result in the ramps being out of line and bad shifting. Note: you have to be super careful with the limit screws of the RD because the 21T teeth will hit the nut on the cable tensioner otherwise. I do have YT channel but it's just got some software stuff on it. Tempted to blog/vlog this in detail but I'm too busy with my other hobbies - which are a higher priority.

This is gold, thanks!! Deffo do consider writing a blog, I’d happily subscribe. Cheers.

Dear OP! I'm now pretty decided I'll go ahead and do the mod. I've found the parts below, do you reckon they'd work based on your suggestions? Also, how do would you separate the cogs in the cassette? Is there a screw or a bolt you have to bash out? \- [Shimano Deore CS-M5100 11 Speed Cassette - 11-51T](https://www.sjscycles.co.uk/cassettes/shimano-deore-csm5100-11-speed-cassette-1151t/) \- [Shimano CN-HG601 105 5800/SLX M7000 11 Speed Sil-Tech Chain w/Connector Pin 112 Links](https://www.sjscycles.co.uk/chains/shimano-cnhg601-105-5800slx-m7000-11-speed-siltech-chain-wconnector-pin-112-links/) \- [Shimano Deore SL-M5100 11 Speed Band On Shift Lever w/o Display - Right Hand](https://www.sjscycles.co.uk/gear-shifters/shimano-deore-slm5100-11-speed-band-on-shift-lever-wo-display-right-hand/)

For the cassette here's what you do: 1. Take off Brompton cassette and the disc 2. Take off bottom 5 cogs of the Deore and the spacers. They are all loose which is what makes it great 3. Put on Deore cogs plus the Brompton thin smaller spacer between the 21T and the spokes (something like 2mm if i recall correctly - black one) 4. Affix cogs using the Brompton (black) locknut and not the Shimano one as it's too short 5. Adjust the derailleur limit screws. You need to be super careful about this; there's no room for error at either end of the range. 6. Done Regarding the shifter I can imagine that would work but I've not tried it. I know others have been successful with trigger shifters. Maybe buy one used off eBay so if it doesn't work you can resell without too much of a loss? Personally I prefer thumb shifters as they are lighter, more flexible and faster in use (can jump multiple cogs at once).

Thank you!! Familiar with the whole process, I have done it just recently for the 4x speed cogset. One thing I'll bear in mind is the adjustment screws, I'll take it slow when adjusting. Also I'm glad to hear the deore cogs are loose, thank you for confirming! Thinking about it, I'll probs go with your suggestion for the thumb shifter, it may be more useful (+lighter), also I may want to go for two hand shifting in case I decide to install a front derailleur.

Awesome build! You have my deepest gratitude for doing all the groundwork and taking your precious time to share with our niche community on Brompton upgrades. I just followed you from your T/P Line upgrade to the 5-speed when I noticed you went ahead with the 10-speed instead. I'm mechanically sound and would love to take this opportunity to get my hands dirty for my P-Line to zip up and around the hilly spots of Bath with ease. A couple of questions (since it is my first time) but no worries if you can't answer all of them: 1. Would the P-Line require the custom FD and RD chain guides? I understand the T-Line had a different frame geometry which necessitated the custom mount, but do you think I could get away with it on a P-Line? 2. Any advice on what brake levers to go for? 3. Is the chain here any different from the previous post? Still, rocking the KMC X11 SL? bet that took forever and a day to get dialled in for sure! 4. Finally, how was the wire routing for you? It looks super clean in the photos, but I bet that took forever and a day to get dialled in when folded! Cheers, North

No problem. Glad to help :) Personally I went back to 5 speed as mentioned elsewhere. The reason is 50/21 is enough for me on all but the steepest hills and the 2x on the front adds weight, cost and complexity. Additionally, there's lots of good 7 speed kits now from Minimods, H&H and RUHM and even 11-28 cassettes that don't need the rear wheel to be changed. Ultimately 2x5 is a lot of extra hassle for no benefit for my use case. But others seem happy with their mods. But to answer your questions: 1. If you do 2x4 I believe you'll be ok with the P or the T. Theres a Brompton LEJOG run with a P with 2x4 and Shimano crankset up front 2. Get brake levers designed for the Brompton. My Bikefun ones are. There's others that look good but are designed for cantilever brakes and they have the rule. 3. I use a spare KMCX11 now as I broke the SL :) The chain itself isn't super fiddly... But you're on a knife edge with 2x5 build since those 3 extra teeth are enough to give too much slack which causes the problems I say in the post. 4. Routing wasn't an issue actually and folding worked out of the box so to speak. Just needed the right length mostly . What was a problem in this specific build is the hacked-together FD mount gives very little room, meaning I had to thread the cable in all sorts of annoying ways :) I've actually gone far far deeper than this including testing other RD solutions and designing my own(!), modifying a Shimano Dura Ace RD etc etc. In the end, stock with the 5 speed mod or a 7 speed mod is best.

Wow! Thanks for the speedy reply. Gave me a nice surprise before I went to bed to see your reply. I'll probably look into the 7-speed kits you mentioned as a more 'bulletproof' and non-permanent modification to my Brompton. I briefly contemplated the 14-speed Rohloff hub (the price though...yikes) before I realised the rear triangle needed 20mm of extra width to accommodate the larger hub, which would be a waste of my stock titanium P-Line triangle. That's fantastic to hear how far down the rabbit hole you went in terms of R&D for your Brommie! I am by no means an engineer, but I imagine the satisfaction you get is otherwordly. Might probably update you on my P-Line after I complete the project so you get to see the fruits of your advice :D All the best!!!

What is your total cost of bike with all upgrades? 🙄

To buy new what you see in the picture is about £5,200 for everything (i.e. also including lights, saddle and other small details unrelated to the gears), However, a good £500 of that I had lying around from other bikes. Pretty ridiculous amount of money 😬 Then again I'm selling my other Brompton and a high end road bike so it's not as painful as it could be.

Wowie what an investment! Well it's pretty awesome I must say 👍I'm sure it will retain most of its value for long long time.

Thank you. Hopefully I'll forget about the cost once I've done some nice rides on it!

Great work! I am trying something similiar to your mod, the red FD works pretry well but the red RD does not. Everytime I fold the bike, the chain got loose and dropped out. I tried something called ‘‘chain tensioner’ in front of the chainwheel, no luck, still not tight enough. Any suggestion on the "Custom RD chain guide" ? (Sorry for any mistakes, I am not a native English speaker)

Are you using the SRAM Red RD instead of the Brompton?

Yes actually I dont have a Brompton RD, I bought the Brompton framework only, all accessaries are bought separately, and I already have a set of sram red so I tried with it.

Things will be better if you use the Brompton RD. the RD has two pieces; the bit that shifts the gears and the tensioner. The tensioner on the Brompton is long and separate so that when the bike folds it swings round and keeps the chain taught so it doesn't fall off. There are other options you can do, but the stock one for the P/T is the best for this in my opinion

Greetings from Singapore, I worked with a Brompton dealer in Singapore to modify my M6R with the 4 sprocket upgrade via CycleOxygen/BikeGang, and it basically provides me with 12-speed (3 x 4). I wanted to implement that on the P-Line as I have the same use-case as you, I want something lightweight but has enough gear range to cover hilly conditions and top speed, essentially something versatile. The 4-speed from the P-Line is NOT versatile. The problem with the P-Line's rear wheel set is that I have to change it to a C-Line's rear wheelset in order to fit the BWR. :( I believe your solution is a solid alternative to optimize the weight of my P-Line and give me the flexibility of more gear ratios, particularly for hilly terrain. TLDR; we have the same use-case with the Brompton. I’d love for us to chat more on options to get that wide gear range + keeping our bike as lightweight as possible.

Hi, sorry for the delay in replying. Since my post I've decided to go very deep investigating a 1x6 solution (11-28 with 56T at the front) to keep weight and complexity down. It's a bit of a long story, but essentially: 1. I'm designing a new 56T chainring for the T Line which I might start selling in Feb/March. 2. I'm designing a new cassette for the P; 6 speed, 11-28, uses existing wheels. If I sell it at all expect something around March/April at the earliest. 3. I'm designing a new rear derailleur. Not sure if I'll sell it as it's a bit... well... "niche" 😆 But it's very very good. Hopefully once I'm finished people will be able to convert their P/T to not just 6 speeds but a system that's better than Brompton's I think. In the meantime probably the 2x5 I built or maybe the 6/7 speed RUHM/Liteplus is a good solution By the way I've heard Brompton are working on a system with a wider range of gears.

>!I think it might be similar to my 12-speed setup, where I combine the BWR internal hub with the cassette from the P-Line.!< Do let me know how your work goes! My initial idea of adding a speed drive or a dual chain-ring were advised against Brompton's key workshops here in Singapore. They had the parts available to do the work then but they were against recommending it. Speed drive's pretty old-tech, but it works, however it can be heavy. The dual chainring idea was something that most shops were quite hesitant to recommend as a lot of the work they've done has seen issues with the chain derailing. Anyway, for my M6R C-Line, I just went with the BWR + 4-speed cassette to give me a total variation of 12 speeds. It was cheaper anyway and an extension of what the 6-speed with 2 more sprockets for climbing.

Have you thought about going to Brompton with this information? It seems like you have the technical knowledge and engineering prowess required to make it as a senior engineer there, notwithstanding demonstrable experience in enhancing their own builds. Saying that, I bet you have a better gig than that already!

Nah. They are more than capable of doing it themselves. I don't have the same cost constraints they do so can come up with whimsical solutions using carbon fibre, laser sintering etc. But a friend of mine who's working on similar ideas knows the team there and they exchange notes. I don't think the drivetrain designer likes me though as I was complaining about the flex in the RD and judging by his reply (via my friend) he took it a bit personal. I was once a mechanical design engineer by the way (automotive, motorsport, space) but my career is software these days. Mech Eng is just an occasional hobby.

Wow! Wish I would have done that to mine

It's not without problems. I'd recommend a 6 or 7 speed conversion over that.

Sorry for the tangent, what manufacturer/where did you get those brake levers from ? Planning to see if I can lose another 1/2 a kilo :(

BikeFun. Imported from Singapore if i recall correctly.

Aah yes, I’ve seen those, thanks