Service & Maintenance

How do I adjust the crankset and bottom bracket?


Details of how to adjust the crankset and bottom bracket are contained within the attached datasheet

Brompton bottom brackets and chainsets are uniquely designed to work with a Brompton bike, with no need to make adjustments.


Bottom Bracket:

The bottom bracket is a non-serviceable item. When it is worn out, it must be replaced with an identical unit. When installing a new Bottom bracket, the cups must be torqued to 30Nm.



From January 2013, a new chainset with a removable 130BCD chainring was introduced allowing easy replacement or fine-tuning of the gear ratios. On bikes older than this, if the chainring is worn, the bike will need a whole new crankset.

When fitting a new chainring, the chainring bolts must be torqued to 12Nm.

On pre-2013 crank arms, both left and right crank bolts must be torqued to 40Nm. On post-2013 crank arms, both left and right crank bolts should be torqued to 30 Nm.

All crank arms must be checked and retightened after approximately 50 miles of riding. Riding with loose crank arms will cause them to fail, potentially resulting in injury. Riding with loose crank arms is not covered under your standard warranty.

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