My orange Brompton came with the standard 6-speed option. While commuting through my more or less flat town I realized that I rarely used the two highest gears. Here are my thoughts about the change to a -12% setup.
| 1st | 2nd | 3rd | 4th | 5th | 6th | |
|---|---|---|---|---|---|---|
| Standard | 2,64 | 3,25 | 4,14 | 5,09 | 6,49 | 7,98 |
| -12 % | 2,32 | 2,86 | 3,64 | 4,48 | 5,71 | 7,03 |
The difference between the standard option using a front chain ring with 50 teeth over the -12% version with a 44 teeth chain ring is not dramatic but you will feel it on the bike. If we assume a pedaling cadence of 70 turns/minute this will result in the speed graph you see above. I do between 70 and 80 turns and that’s the background for my calculations.
70 turns/minute is not too fast even without clip pedals and a high cadence is a good thing when riding your bike (endurance instead of power). Speed depends on your fitness first of all – it is not the two kilos less of the titanium Brompton – it’s muscles and training.
For myself I experienced that, with the standard setup, I rarely used the two highest gears – between 27,26 and 31,15 km/h for the 5th gear is to fast for me commuting to and from work (70-80 turns…). Changing the front chain ring gives me a speed of 23,98 to 27,41 km/h for the 5th gear and this is more the range I need. If I’m on a comfortable ride I choose the 4th gear with 80 turns and a speed of 21,5 km/h. If there is some power left in my old and used legs, I switch to the 5th gear, cadence drops a little bit and I ride around 23-25 km/h. On a good day the 5th gear is good for a speed close to 30 km/h – down a hill I still have the 6th left.
There is one disadvantage of the -12% option: I’m shifting more frequently. This is no big thing with the rear hub but it is one with the two sprockets on a Brompton. If you are used to the crisp shifting of a state of the art derailleur, then the Brompton shifter is a big disappointment. It takes time to shift between the two sprockets and you have to reduce the pressure on the pedals. Switching from the 4th to the 5th gear does involve both shifters: one step up with the hub and one down for the sprockets. That´s the price to pay here…
When I bought my Brompton, my dealer didn’t even mention the -12% option to me. I don’t think many will touch this subject – they just sell the standard. With a better derailleur (the “chain pusher” is the problem) the -12% option would be the perfect solution for most riders. Given the performance of the shifting as it is now, it is a 50:50 decision.
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One response to “6-speed gear ranges and ratios”
How to change the rear sprokets on a Brompton
Hi can you help my m6l when in the 1st and 2nd gear when I peddle makes a noise and up hill it makes a louder sound than the 3 4 5 6 gears that are almost silent. U can also fell a little though the peddles when rideing I was told all brompton bikes 6 speed the two lowest gears make noise when rideing?