It took some figuring out, but I’ve got a Rohloff 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 8.11vm). The bike folds exactly as normal, with one exception – the cranks won’t rotate backwards all the way around as the wider rear triangle gets in the way. I found as long as I remembered to put the cranks in the right orientation before swinging the rear triangle under – a matter of a second to do – it works perfectly.
The conversion involves fitting a complete new rear triangle, which I make in stainless steel. The kit is pretty simple to fit – replace the rear triangle, fit the new wheel, fit the new chainset onto the same bottom bracket, fit the shifter and fit the cables.
If you prefer, I can fit the kit for you – either to your existing bike, or if you order a new Brompton and send it to me. Fitting is free. Or if you prefer, I can build up a complete bike for you – see the Rohloff Brompton Order Form.