So I let the chain wear down too much in the past two years and the rear sprockets appear to be worn out and will need to be replaced. The stock 50T chain ring is also showing signs of wear but appears to still be good for a few years.
I wanted to use this opportunity to see whether I could switch the gearing up a little.
The 13-16 gearing has been surprisingly capable but I need just a little more hill climbing ability; the lowest gear (2.64m) is just barely enough sometimes. I’d like it a tad lower I think.
On the high end, I usually ride in the upper two gears on flat ground. The highest gear (7.98m) feels just a tad too much sometimes though and I then fall back to one lower (6.49m) but that feels a good bit too low. That doesn’t bother me a lot but it’d still be nicer to have a gear that’s just right.
On a downhill, the highest gear is always sufficient for me; feels pretty much exactly right. I wouldn’t mind slightly more metres of development but, honestly, I don’t care very much when I’m already going way past 30km/h and I don’t ride downhill for very long usually. I’m unsure whether reducing the highest gear slightly would make me pedal uncomfortably quickly down hill though.
Stock and current config:
| Hub | 64% | 100% | 157% |
|---|---|---|---|
| Low sprocket | 2.64 | 4.14 | 6.49 |
| High sprocket | 3.25 | 5.10 | 7.98 |
I’m currently thinking about a 44T chain ring with 12-17:
| Hub | 64% | 100% | 157% |
|---|---|---|---|
| Low sprocket | 2.19 | 3.43 | 5.37 |
| High sprocket | 3.10 | 4.86 | 7.61 |
or 12-16:
| Hub | 64% | 100% | 157% |
|---|---|---|---|
| Low sprocket | 2.33 | 3.64 | 5.71 |
| High sprocket | 3.10 | 4.86 | 7.61 |
The lower gears being lower and closer together sounds very nice.
In the higher gears, my hope is that the slightly lower highest gear would allow me to use it the majority of the time on flat ground because I suspect the second highest gear would feel quite a bit too low as a fall-back.
I could see 12-15 being an option perhaps but that also gets the lowest gear much closer to 13-16 again:
| Hub | 64% | 100% | 157% |
|---|---|---|---|
| Low sprocket | 2.48 | 3.89 | 6.09 |
| High sprocket | 3.10 | 4.86 | 7.61 |
But obviously the lowest gear gets very close to the previous config again.
Where I have a hard time is imagining how significant the difference between 2.64m, 2.19m, 2.33m and 2.48m are in an uphill scenario. The jump between the lower gears in 13-16 (3.25m to 2.64m) in practice feels significant but not that large either and we’re talking about a much lower absolute drop being gained in the low end by switching gearing. I don’t know whether the practical effect of this is linear though and I suspect it might not be.
I’d really appreciate practical experience here. Have you changed gearing on your Brompton? From what to what and how significant were the differences?
The only time I rode with close gearing was crit racing. I rode standard 53/39 11-28 through the 8-11 speed eras on road most of the time. That worked well for pretty much everywhere for me. I can get away with never using my inner ring so long as the slopes stay below 6 degrees. When I first started commuting hardcore, I rode a 55/39 with a dura ace triple FD and a range of everything from 11-21 - 11/23 - 11/25 - 11/28.
You need to know your rear derailleur capacity to know what will potentially fit.
Unless you’re trying to improve your times on a 66 mile round trip daily commute to work, or racing where the differences between riders is miniscule and the perfect gear to sit on a wheel might make of break your race, I would go for the widest possible range your FD/RD can handle. You’ll never regret having the extra easier or harder gear to pedal in. If you are never pedaling down hill or in a tailwind, skip the hardest end. If you never see a climb skip the easier. If you like to explore and go wherever life takes you, keep your range as wide as possible. If you do not have the ideal comfortable gear, spin the lighter one faster and consider it cadence training. If you keep at it, within a few weeks you will begin to have a faster average cadence. This is part of race training as higher cadences are more efficient overall. Some people train on a fixed gear or single speed at times to push themselves to higher cadences in unique ways.
Right but I do like to ride fast when possible. It’s not for competitive edge or anything; it’s just comfortable.
The main thing I want answered is whether the difference in metres of development in the low end actually makes a difference and how significant they are in practice.
