Brompton G Line bottom bracket from Brompton

Brompton G Line bottom bracket cartridge - JIS 123 mm

The bottom bracket comes does not come with crank bolts

This Bottom Bracket is only compatible with the G Line 20 inch wheel size Brompton bike - though not the G Line Electric

The G Line has a 68mm bottom bracket shell the same as a standard Brompton, but with a longer spindle length

Removal

Before removing the bottom bracket from your Brompton, you will also need to remove the crank arms (this whole process will be easier if you have a workstand)

Note: The drive side of the bottom bracket undoes reverse to a normal thread - so righty loosey (clockwise)

Note 2: you need to re-use the crank bolts from the old bottom bracket 

Installation

Do not grease the plastic threads on the bottom bracket - the plastic itself will act as a lubricant

Note: The drive side does up lefty righty (in a anti clockwise direction) - not normal tightening - the non-drive side tightens up "normally"

It should be tightened between 24Nm to 30Nm

Crank bolts should be tightened to 30Nm

We made the video below to show how to remove the old bottom bracket from a standard 16 inch wheel size Brompton - the G Line process is exactly the same

Once the cranks are removed, you can remove the bottom bracket itself

This other great article from Park Tool shows how to remove and install the bottom bracket

Brompton 2021 Q part code: Q103998