Speedier 3-speed Brompton?

[brooklynbrompton]

Hi all. I have a 3-speed Brompton and would like to increase resistance on flats and downhill. I was thinking of swapping out either the front chainring or the rear cassette. I was concerned about messing with the spacing / size of the chain itself so that it continues to run smoothly. Any suggestions? Thanks!

 

[tyred]

I am assuming that you have the Sturmey Archer hub gear so you can either fit a smaller rear sprocket or a larger chain ring.

Changing the rear sprocket is cheap and easy as it is held on with a circlip thing which is easy to pop off with a small screw driver.

Count the teeth on your rear sprocket. I think 13 tooth is the smallest you can get. If you already have a 13 tooth sprocket then you will need to go down the more expensive route of changing the chainset.

 

[rogerzilla]

54 x 13 is the biggest stock ratio, I think. With the 33% increase from the standard hub, that would give a 90" top gear, which is like using the big ring and the middle of the cassette on a road racing bike. You must use the correct chain length, or folding may be a problem - Brompton publish a table.

https://trade.brompton.com/Uploads/QPart/QPart-Datasheets/ds-chain.pdf