Brompton Forks & Rear Frames


imageThese Brompton-compatible rear triangles were designed for my Rohloff Brompton kits, but are suitable for fitting most standard rear hubs to a Brompton. The design has been refined over 10 years of making hundreds of Rohloff Bromptons.

Made entirely from 304 marine-grade stainless steel, they won’t rust – you can have one in brushed stainless steel finish, or powdercoated to match the rest of your bike. They have a lifetime warranty, like everything I make.

The rear frame has a 135mm OLN width (the Brompton normally is 115mm) so will work with most standard hubs like the Rohloff and Alfine. It has IS disc brake mounts and has enough space for a 160mm rotor They work with normal Brompton frame rollers and Eazy wheels, brakes, and the standard elastomer. Standard mudguards and rear rack will also fit, and if you use a Rohloff it also uses the standard Brompton single-speed tensioner

 Brompton-compatible rear frame – £395 
 Brompton-compatible rear frame, integral rack – £485 


brompton forksI also make Brompton-compatible forks – designed for my disc brake kits, these are suitable for fitting standard 100mm-wide front hubs into the Brompton – not just disc brakes but electric motors and standard-width hub dynamos will fit.

They are made from Columbus Zona tubing with investment-cast crowns and fork ends, and come with the correct fittings for the Brompton mudguard and handlebar catch.

 Brompton-compatible forks – £295 

NEW: 20″ Frames and Forks: I’m now making these for larger wheels – they will fit 18″ x 2″ fat tyres (Birdy size), or 20″ x 1.3″ slick tyres – see the wheel size page for more info. Pricing is the same as for the standard rear triangles, just say you want 20″ parts instead of 16″ when you order. The standard Brompton rack and mudguards still fit these parts (with a little tweaking).

MTBrompton Frames and Forks: These parts will take up to 20 x 2.4″ tyres, as on the MTBrompton bikes I’ve built.

MTBrompton rear frame – £445 
MTBrompton forks – £345

88 Replies to “Brompton Forks & Rear Frames”

    1. My rear triangle is about 100g heavier than the standard steel Brompton one. My integral rear rack is lighter than Brompton’s rack, so my rear triangle with integral rack is about the same weight as the Brompton rear triangle and rack.

      My forks are the same weight as the standard Brompton forks.

      The Brompton titanium part are, in total, about 740g lighter than their steel ones – that’s counting the folding pedal bolt and mudguard stays.

    1. They’re built for 160mm rotors. The Brompton levers work well with the BB7 Road version, the Mountain version has the wrong leverage ratio.

    1. I’ve never tried – they should do, as the bolt sizes are the same – they would attach on the outside of the rack not the inside, though.

  1. Ben, do you offer your rear and frame in titanium please. I see an option in the full build for Ti but I’m unsure at this stage if I want th full build. So I wanted to get the rear frame and fork only.

    Builtiful bikes though.


    1. For 349, the limit is really the usual Brompton sizes – so up to the Marathon Plus in 349. The problem is the chainstay bridge which has to be where it is otherwise the seatpost hits it when it folds. I’ve never tried 355 wheels, but I’d guess they’d work with thinner tyres – not sure why you’d want to, though.

      If you go smaller, you can go fatter – the 16″(305) x 2″ Big Apple tyres fit okay.

      1. That’s extremely helpful, thanks very much for the info. Is the rear triangle available with a derailleur hanger? thanks in advance.

        1. I can make one with a derailleur hanger, but no derailleur takes up enough chain to allow the bike to fold without the chain becoming slack.

          1. What about using a long cage MTB derailleur with a single chainring? Would that take up enough slack?

          2. No – tough a wire loop similar to how Birdy did it would work. You wouldn’t be able to back-pedal when folded thigh, and the mech would be pretty close to the ground.

          3. It’s quite true that a derailleur won’t take up enough slack when the bike’s folded, but it still works – you just have to be very careful when folding and unfolding. I’ve had a derailleur setup for a year now, and it’s fine.

  2. Hi Ben ! Do you make stainless forks ?
    (I ask because it would be great to have both triangle and fork in brushed stainless steel finish)

  3. I want to convert my 6 speed brompton rear brakes to disc brakes only keeping my current gears wheel etc. Is this possible if i purchase the rear triangle and disc brake kit ?

    1. No, your current rear wheel is not disc-ready – the only way to do it is to get a new rear hub – Alfine, NuVinci or Rohloff.

  4. Hello,

    Have you ever thought about up-sizing fork and rear triangle to take 20″ wheels?

    Obviously its a major modification, a new bicycle pretty much, and so would require some careful planning/testing to get it folding okay and to maintain BB height (perhaps 1 or 2 cm higher). Still I think that it would be an interesting compromise. I would be interested, for a start, perhaps others too… Folded, the package wouldn’t be so small and neat as a standard Brompton, yet I am sure that it would still retain a huge advantage over other 20″ folding bikes (Dahon, Tern). With a slightly bigger drop cover it would still be easily stowed on the train, perhaps too on the bus and in the Metro.

    After some experience with a 20″ folding tandem (Pedal Power Butterfly), which make with 50-405 Big Apple and is now on 55-406 Big Ben, and I really appreciate having such a choice of tyres, which I would like for my solo bike too. Touring two-up on the tandem, with my daughter, we can easily roll over loose gravel where the Brompton would get stuck, running 35-349 Marathon Plus, even with my wife riding (and she’s anything but chubby…).

    In the meantime, I have well noted your suggestion of using 16″ wheels so as to have a better choice of tyres (50-305) while still using standard frame. I’m not too sure if and how I could get the rim brakes working again on such a set-up (rim diameter nominally reduced by 22 mm). Perhaps that suggestion pre-supposes using a bike that has already been converted to disc brakes?

    Neil Dewhurst – Lyon France

    1. I have been considering it. The back isn’t too big a challenge, I can make a longer rear triangle, it’s the front that’s tricky – fitting longer forks for 406 would raise the front by about 6cm, which is quite a lot. So the way to do it is to probably modify the front of the main frame too, changing the head tube.

      As with most of these things, it’s a project that has to wait for someone to actually order one – I don’t have time to build these things on spec 😉

      The 16″(305) wheels only work with disc brakes, yes – they don’t fit the standard frame anyway, they only fit my rear triangle and forks.

      1. Hi – I am interested in this possibility too. I’m trying to understand why/how the head tube would be changed. Thanks!

        1. The problem is that fitting a 20″ wheel means raising the front of the bike by about 6cm. That’d make the bottom bracket pretty high and also affect the handling if we don’t correct for that.

          1. Thank you for explaining – that makes complete sense. I really like how the Brompton handles with the weight being quite low. I will get in touch when I am ready to upgrade my Brompton!

  5. May I ask you about Brompton titanium rear frame units? I woukd like to fit one. Do you have them for sale? Are the ones as seen on offer on Ebay genuine or copies from Asia? Is there any way to tell if one of these is genuine Brompton or not. I understand they are made for Brompton by another company hete in the UK.

  6. Hi- I was looking at the recent photograph showing the difference between the old version of your Brompton rear triangle and the new version. Does the change in the style of the dropouts mean that your current version will take a QR Rohloff or does it still require a nutted hub?
    From the photographs which you have put on your website, I get the impression one or two of the recent Rohloff Bromptons which you have put together use a QR.

    1. All of them use a QR hub now, unless you specifically ask for a nutted hub. I normally use an Allen key skewer, though, to save a bit of width.

  7. How do the 16″(305) x 2″ Big Apple tyres ride (comfort, rolling resistance) as compared to the standard 349 Brompton tyres?

    1. Not the main frame, no – they’re not available separately from Brompton, you have to have a complete donor bike to start with.

  8. Hi, I have a Dahon folding with fabulous Sram Dual Drive 3×9 drive train. I am thinking of putting such a rear hub onto a Brompton frame. The OLD is 135mm. Will your rear frame work well for it? Do you have suggestion such configuration? My concern is the “thickness” of the bike being folded. Do I need a new frame hook? Will the folded bike still fit into the B+W case? Thank you.

    1. The tricky bit is going to be the derailleur – I can make a frame with a derailleur hanger, but it’ll get pretty close to the ground in some gears, and when folded the can will be loose. It should still fit the B+W case, it’s about 20mm wider – you shouldn’t need a new frame hook.

      1. Thank you for the expert opinion, you are right, the ground clearance of the derailleur may be the bottleneck issue. I generate good power so I will use close-range cassette, with largest cog being 21, and set chain at highest possible tension. Can short-case derailleur be used and the rear wheel still swings folding well? Love the Sram Dual drive, perfect companion to small wheel, kind of equivalent of a car’s CVT to me, speed transition is so smooth and easy. Simply exciting to imagine my Brompton can be fitted the same. Can not find any such conversion in the whole universe. 27-speed Brompton, why not? Thanks again for your advice. What will be the distance between the lower edge of the derailleur hanger and the ground?

        1. I did some close observation of my Dahon 20″ with Sram DualDrive drivetrain. You are absolutely right, even for the 20″ wheel, when in low gears, the short-cage SRAM derailleur almost touched the ground. Thanks again for your expertise.

  9. Actually, it is still very doable with Brompton. I experimented with a more compact Shimano deraulleur and at lowest gear (28T), there is still quite a bit clearance from the ground (20″ Durano 1.1″ tire), so it should have adequate clearance for Brompton’s 16″ wheel with fatter tire, more if the lowest gear is less than 28T (25T or 23T). I wish I could attach some pictures. I ride the Dahon almost every day, the Sram DualDrive is a fabulous 27-speed system, in essence, Brompton’s 6-speed is a “Dual Drive” too, isn’t it? I may contact you later to start the project that is temporarily on the back burner but I believe it is very doable unless the chain will rub the rear frame. Minimal weight gain, if any, that is the good news over the 6-speed.

  10. Hi, Wonder if have done any 1x drive train on Brompton? Do you think if the 1x on Tern verge can be done on Brompton with your rear frame of 135mm spacing with a derailleur hanger tab? This will be a much lighter wide gear range. Your thoughts? I really want a multi-speed “mini-roadie” Brompton with finer gear gaps, with bullhorn bar to stretch out my 5’8″ body for long distance riding and perhaps Brompton World Championship race (if legal). I can ride long distance with good comfort on my Dahon Vector 27H with bullhorn bar but it can’t be taken inside aeroplane cabin . Thank you.

  11. Hi, I have a Brompton M6L from 2006 which I now look to fit a Rohloff hub, belt drive and disc brakes. I already have a Rohloff hub on a Surly bike so know the Rohloff hub well. My question is, if fitting a Rohloff to the Brompton with belt drive, is a 19 teeth rear cog/sprocket/belt carrier the smallest you can go? The reason I ask I would like to have a slightly higher gearing with top around 100 inches, so to achieve this would a smaller rear belt sprocket carrier be available? Maybe the gearing with a 19T rear giving a 17″ bottom gear is perhaps too low meaning you would never use the lowest 3 -5 gears of the Rohloff so such a waste. A 70 teeth front belt carrier looks like it must be at the maximum limit? I would like a belt drive over a chain as I am attracted to the very low maintenance. And fitting hydraulic disc brakes – as nice as Hope brakes are, could say Shimano SLX be fitted instead? Do your Rohloff kits include the shifter cables and twist grip shifter as Rohloff sell them? Advice greatly appreciated.

    1. 19t is the smallest belt cog possible on the Rohloff, no-one makes anything smaller – but remember that the belt pitch is different with belt compared to chain, so the 70t belt cog at the front is more like a 56t chainwheel in size.

      I’ve never tried Shimano brakes – the callipers should fit fine, I’m not sure about the levers. The reason I use the Hope Race X2 brakes is the levers are very low profile which means they don’t get in the way when the handlebars fold.

      The Rohloff kits include the shifter, cables and all the fittings you need.

    1. I wouldn’t say never, but to be honest I can’t see the advantage on the Brompton – it’d make it wider, and fitting the tensioner would be trickier.

  12. I’m interested in the Rohloff/disc conversion with the Big Apples. Is the disc conversion fork the same for standard size tires as it is for the Big Apples? How about the rims? Do you spec the same rim for standard size tires and the larger Big Apples? Thank you for taking the time to answer my inquiries?

    1. The fork and rear triangle are the same for Big Apples, but the rim is a different size, as are the tyres – normal Brompton wheels are 349mm, the Big Apples are 305mm.

  13. Hi Ben,

    I’m strongly leaning toward ordering a new build of your Rohloff Brompton with a chain drive. I have a question about the SON disc hub option. Is it possible to add in USB device charging? I’d like to be able to charge a phone or other USB device during the day, when the power from the hub isn’t needed for the light.

    I found that the Busch & Muller Luxos U light has built-in USB charging and a buffer battery, but it seems to be big and I don’t know if it would fit on the Brompton. Or maybe there’s another USB charging option that would work with the Edelux II lighting?

    1. Yes, the light needs to be quite small to fit under the front bag, but separate devices like the USB-Werk are good and can be fitted to the Brompton stem or alongside the front frame.

  14. Does your frame fit older Bromptons from late nineties early 2000s? or is the design different enough that the triangles are not compatible? I find some compatibility talk about the MK2 and MK3 confusing.

    1. The rear frame will still fit, as the rear pivot dimensions didn’t change. Very old Bromptons have 1″ forks at the front, so if you need that then I can make forks with a 1″ steerer instead of the usual 1 1/8″.

  15. I have a 1991-1992 MK2 brompton that has a broken triangle or rear frame. Do you have it in stock or probably can make it with the same speciation. How much is the cost for it and shipping to Jakarta 12830 indonesia. Thank you

  16. I saw the comment about fitting a new rear triangle on an old Brompton. I have a 1989 version and was thinking restoring with all new parts. I’ve found that fitting a newer hub might be an issue (from what I gathered from blogs about it’s OLN), as well as upgrading to a 6 speed. I would like to know whether your rear triangle frames fit and oldy like this one? Thanks!

    1. My rear triangles will fit an electric Brompton, but the forks won’t work as the Brompton front hub motor is 74mm wide not 100mm.

  17. Hi Ben, I could do with a new rear frame and hinge for my mk2 Brompton. Is it possible to have a stainless steel frame with 115 OLN? Folded width is a constraint and also I like Sturmey AWs!

  18. Hi, can you fit a standard Brompton rear rack to the 20″ rear trangle?

    Also do 20″ x 1.3″ tyres actually give any shock absorbtion? If not a rider may actually get more pinch punctures than with the 16″ tyres.

    1. The standard rack does fit to the stretch 20″. 1.3″ tyres have less shock absorption than the 2″ ones, but they’re similar to the standard Brompton tyres – as long as you keep them at a decent pressure, you don’t get pinch flats.

  19. Hi Ben, which bottom bracket do you use and which quick release for the rohloff?
    The chainline remains the same as with the conventional hub,
    regards Karl

  20. Hi,
    Can I have the alfine 11 speed kit (rear triangle ,chain and wheel) attached to a new 2021/2022 frame (by you) and a front fork shipped across to India? is this custom order possible?

    1. Black lacquer is tricky, it’s not one of the colours our powdercoater has at the moment, but gloss black works well with a black lacquer mainframe.

  21. Wow, really excited that you’re now making 20″ rear frames and forks for really fat tires! Is the MTBrompton rear frame available with a derailleur hanger for use with the Microshift Super Short drivetrain system?

    1. The solution at the moment is to make a belt-ready frame, and use a derailleur insert – I have them in stock. I’m thinking of making a derailleur hanger that works on the standard frames as well.

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