Brompton - changing the ratios on a 2 speed

[Fastpedaller]

I recently added an unused 2007 Brompton (2 speed) to my fleet - I had an earlier Brompton (3 speed) about 30 years ago which I regretted selling. I thought I'd post this info in case it's useful to anyone........ My first ride established that I wasn't happy with the large jump between the 2 gears, although the lowest gear was ok for starting off and hills. My 'Fastpedaller' label is in reference to my cadence, rather than my outright speed along the road :-). So my quest was to make the highest gear lower, and I achieved this by removing the spring clip from the freehub, and fitting a 'less-small' smallest sprocket from my collection of partially worn Shimano sprockets off 7 speed cassettes. Shimming with the correct diameter of spacers ensured the spring clip could be refitted and the gear change would still function correctly. Result - closer gearing so I'm not struggling in the highest gear.

 

[Kell]

Good on ya.

I have to say I find high cadences on the Brompton hard to maintain (too much ‘Bob’ on a standard suspension block), but each to their own.

 

[rogerzilla]

Mine's running 13/15 at the back. Dura-Ace 15T and ZTTO 13T, with appropriate spacers.

 

[ukoldschool]

Weird timing for this thread - I switched my 6 speed rear wheel out for a 2 speed today as I dented the rim on my 6 speed wheel so am waiting for a new rim to be delivered to rebuild it, I put the cogs from my 6 speed on (12 & 15t) and whilst is was OK, i really span out in top gear, to he point I couldnt keep up with traffic here in London. Its ok as a temporary stop gap, but the lack of top gear would mean I dont think I could run this FT, which is a shame because the bike feels a lot lighter (because it is ).
I think Ill try a 54t front cog, and investigate the DIY 3 speed options before I inevitably go back to the 6 speed. Its a shame a 4 speed rear wheel isnt easier to get running on a B as that would be probably perfect for me with a big (60t) front cog.

 

[12boy]

When I use my rear wheel as a 2 speed I like 12/17. This is coupled with 58 and 37 tooth chainrings that I can manually shift for steep ascents. BikeGang gave me a one piece 11/14/17 sprocket to demo and after many thousands of miles the sprocket still works out fine although I had worried about the 11 tooth part wearing out too quickly. The only advantage to the 177% SA IGH I also use is the high gear is quite a bit higher than the 11 tooth provides. The Shimano sprockets work well except for the 11 tooth.

 

[ukoldschool]

I put the 54t on, still hopeless spinning out
luckily the rim and spokes arrived from SJS so ive rebuilt the rear sturmey wheel, just need to true it up

 

[berlinonaut]

would be probably perfect for me with a big (60t) front cog.

I put the 54t on, still hopeless spinning out

From experience I can recommend using a 60t chainwheel on the 2-speed if you are not a king of cadence but still want to go way faster than ~25kph continuously. I usually run a 60t in summer and a 54t in winter, when I'm less fit, on my 2 speed.

 

[ukoldschool]

I have to admit I like the 'racy' feel that the 2 speed has, you can def feel the reduced weight and improvement in drivetrain loss from not having the IGH.

 

[ExBrit]

From experience I can recommend using a 60t chainwheel on the 2-speed if you are not a king of cadence but still want to go way faster than ~25kph continuously. I usually run a 60t in summer and a 54t in winter, when I'm less fit, on my 2 speed.

So do you have a winter and a summer chain or do you replace the chain each time you swap the chainring for the season? Or do you somehow run the same chain with both chainrings? Cuz I'm liking this idea.

 

[berlinonaut]

So do you have a winter and a summer chain

Exactly that, it is the least stressful solution. But I have to admit that since covid things started to get a bit out of order regarding my commute and fitness plus I mounted a power meter on the 2-speed out of curiosity and this is Hollowtech with direct mount chainwheels, so I am stuck at it's 53t/39t at the moment. To compensate for that I sacrificed my 9-gear modded touring Brompton (as it turned out the Rohloff Brommi superseded it in practice and it only collected dust) this summer and converted it into a S2Ex with somewhat lower bars than I usually ride and Scorchers for speed and comfort - and the 60t chainwheel. The luxury of having a herd of Bromptons...

 

[Tenkaykev]

The luxury of having a herd of Bromptons...

Shouldn't the collective noun for a group of Bromptons be a " Fold " ?
( other suggestions gratefully received )

 

[ukoldschool]

Trued up my new rim on my BWR hub yesterday so thankful to be back in the land of gear ranges again today. The 2 speed was a nice experiment, but it wasnt for me.

 

[mitchibob]

From experience I can recommend using a 60t chainwheel on the 2-speed if you are not a king of cadence but still want to go way faster than ~25kph continuously. I usually run a 60t in summer and a 54t in winter, when I'm less fit, on my 2 speed.

Sounds like you should've been at Urban Hill Climb last weekend! A 60T has won folding bike category before. Personally, I was struggling with 44T this time (really didn't prepare for it).

 

[berlinonaut]

Sounds like you should've been at Urban Hill Climb last weekend! A 60T has won folding bike category before. Personally, I was struggling with 44T this time (really didn't prepare for it).

At an "Urban Hill Downclimb" my chances would probably be better. Today ist the yearly "Brompton on Brocken" event where a small crowd of Brompton riders ride up the Brocken in northern Germany. However a fun event, not a race. It is not too tough, not too long and most of the time not too steep either, still I enjoy rolling downhill more there (and did pass the 70kph mark massively on the Brompton). This year I have to pass unfortunatey due to other obligations, but waiting eagerly for the reports of participants coming in.