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 8.11m). 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 a very modified rear triangle, so I’m offering two ways of converting your bike - you can send me your existing rear triangle and I’ll modify it*, or I can send you a complete new rear triangle. Or, if you like, I can do all the fitting here, as I’ve done with this older Brompton.

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.

Rohloff Brompton Kit - using your triangle - £1195
Rohloff Brompton Kit - using new triangle - £1395

*Do I need to mention that your rear triangle will not work with the normal Brompton gearing after I modify it? Also, as this involves removing dropouts and brazing on new fittings, I can only do it to a steel triangle. I might be able to do it a bit differently if you want me to have a go on a titanium triangle, but I haven’t tried this yet.

There’s also no theoretical reason why this couldn’t be combined with a Mountain Drive or Speed Drive - with a Speed Drive and 42t chainring, you’d get 28 gears from 15” to 130” - but that’s just silly...