Chain tensioner

Brompton Standard Chain Tensioner for 1 and 3 speed Brompton folding bicycles

Also suitable for 5 speed Brompton folding bikes

This is one of two types of chain tensioners used on Brompton folding bikes

• Standard chain tensioner (no derailleur) - this one

• Derailleur chain tensioner (for Brompton bikes with two rear sprockets)

The Brompton chain tensioner is one of the "essential" list of spare parts for Bromptons with a single rear sprochet and performs an important role in keeping the chain taut whether the bike is being ridden or in the folded/parked position

It works using a big spring (internally) to keep the chain under tension

The chain then glides over two jockey wheels - these wheels will wear over time - they are changeable. To make the jockey wheels last longer, keep your chain clean and not over lubricated

This chain tensioner internally geared hubs where only one single rear cog / sprocket is fitted (1-speed, 3-speed or the older 5-speed).

The chain tensioner shouldn't be done up too tight (just over finger tight - approx 5NM for Sturmey Archer and approx 8NM for SRAM hubs). If it is over tightened then you will crack the plastic of the chain tensioner

Brompton derailleur chain tensioner for 2 and 6 speed Brompton folding bikes

This chain tensioner is for Brompton folding bikes with 2 speed, 6 speed SRAM or 6 speed Sturmey Archer / BWR (Brompton Wide Ratio) gears.

This works as a chain tensioner (keeping the chain tight when riding and folded) and as part of the Brompton designed derailleur mechanism - by having juckey wheels which can move from side to side to allow the chain to move between the two rear sprockets

To make your chain tensioner last as longer - keep your chain clean and not over lubricated