What are the Brompton gear ranges and ratios?

Brompton uses a range of gears that are best suited to the multipurpose functionality of the bike and the wide range of riders that use a Brompton bicycle.

Internal gear hubs are a well-proven design and are simple to use, adjust and maintain. They add a little weight but give an incredibly long service life in normal use.

Our exclusive 1 and 2-speed freehub is super light and extremely reliable. The Brompton derailleur system is designed specifically to give optimum shifting on the short stays and small wheels of the Brompton bicycle.

We offer several different gear options and dealers will make recommendations depending on your specific riding conditions: 

1 speed – For flatland riding. Bromptons lightest gear option. Perfect for riders looking for flat terrain riding without hills, perfect for a stronger rider with a view towards speed and simplicity. This can be upgraded to 2-speed.

2 speed - This adds an additional gear at the rear with a unique Brompton designed changer mechanism and shifter. Mainly oriented at flatter riding conditions, two gears allow for a slightly lower gear range for the occasional low hill. This can be converted to 1 speed.

3 Speed - Three gears allow the rider to tackle varied terrain with a super reliable internal hub that needs minimal maintenance or adjustment.

6 Speed – This redesigned Sturmey Archer hub combines three wider internal gear ratios and our compact 2-speed gears externally to give a total of 6 gears. This will help to tackle hillier and more diverse terrain.

All gears can be reduced by a certain percentage (to make them lower) by changing the front chainring for a smaller option.

1 and 2-speed bikes come as standard with a 54t Chainring giving gears matched for speed.

3 and 6 speed systems use a 50T chainring to give a wider overall range. So, moderate speed but reasonable hill climbing too.

Brompton bikes can also be fitted with a 44t chainring reducing the ratios by 18% for very hilly conditions.

In all cases, the chain length will need to be adjusted to accommodate the new chairing size.

All three chainrings are interchangeable, having a 130mm BCD so some experimenting is available for the more adventurous. The largest rear sprocket that can be fitted on 2 and 6 speed systems is 16 teeth.

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