It is common to replace the complete chain tensioner assembly – but it’s possible to replace just the jockey wheels and associated components to save some money.
This derailleur jockey wheel pack consists of the following items:
Pair of jockey wheels (idlers) for derailleur (2 or 6 speed) Brompton chain tensioners – 10 tooth
Bearings (pair – approx 19mm long with a diameter of 6mm
Fixing nut (approx 31.5mm long) and bolt (pair)
It allows you to replace just the worn jockey wheels on a Brompton chain tensioner.