It took some figuring out, but I’ve got a Rohloff 14-speed hub gear conversion working happily on the Brompton 😉
The gear range with 13t rear cog and 54t front chainring – both completely standard – is 19” to 102” (1.54m to 8.11m). That’s a very wide gear range, as wide as a touring or mountain bike, with a low enough bottom gear for almost any hill – and being a sealed hub gear you can select any gear at any time with one twist of the shifter.
Don’t already have a Brompton? No problem, I can build you a complete new one – see the Rohloff Brompton Order Form.
Can this kit fit to any Brompton? Yes – the rear triangle I build will fit any Brompton made in at least the last 15 years. The kit replaces your entire gearing system, so it doesn’t matter what gears you have at the moment.
Does the bike fold as normal? Yes, with one exception – because of the wider back hub, the cranks won’t rotate all the way around when the bike is folded. The best trick is to put the cranks horizontally with the left pedal forwards, then fold as normal, this will put the pedals in the best position.
Does this make the folded size bigger? Yes, it makes it about 15mm wider – the exact amount varies a bit depending on what handlebars, shifters, brake levers and rear rack and other parts you have. The bike still fits into the original Brompton cardboard box, however.
How much weight does this add to the bike? It adds about 800g over the weight of the 3-speed Brompton.
Will the Rohloff shifter work with all handlebars? It will fit to all bars, but with the M- and H-type there isn’t much space left, so bar ends won’t work. There’s more space with the S-type and P-type.
Is the kit hard to fit? Not especially – the trickiest bit is removing your old rear triangle, the two pivot bolts can be quite solid. I do it with an impact driver, good long 4mm Allen keys usually manage, but occasionally the bolts have to be drilled out which means you need a new rear hinge kit. The rest is pretty simple – fit the new rear triangle, fit the rear wheel, mudguards and rack if you have them, fit the other parts and so the gear cables.
Can you fit the kit for me? Sure, no problem – there’s no charge for fitting if I do it here.
Does the rear triangle have to be painted? No – being entirely stainless steel, I can leave it as a brushed finish if you prefer.
What is the integral rear carrier? Normal Bromptons come in a couple of versions, the L-type with just mudguards or the R-type with an aluminium back rack as well. The kit I make works perfectly with these parts – you can still have just mudguards or the Brompton rear rack. However I also make a version with an integral carrier, made out of the same stainless steel as the rear triangle and permanently brazed on. It is lighter and stronger than the Brompton aluminium carrier. Normally it’s quite a minimalist carrier as in the pictures above, only intended to hold the mudguard and four castor wheels, but I have also made wider versions intended to carry top bags.
Can it have a belt drive? Lots of people ask about this. I think it can be done, but it does go against Gates’ recommendations for the belts as the belt has to double back when folding. If you want to try, it’d add £250 to the cost – if it didn’t work then you could always go back to chain drive and I wouldn’t charge you for the belt.
Pictures below show some of the Rohloff Bromptons I’ve built – note that some are earlier versions, so are built a bit differently to the way I make them now.