Bottom Bracket Repair

This week, we attempt a bottom bracket repair on touring bike with a very loose crank. A while back, I had a bike in to replace an external cable box on a Rohloff Speedhub equipped touring bike. The same bike is back, this time with something seriously amiss in the bottom bracket area.

The first job was to remove the crank from the square-taper but this proved difficult. Both were so tight, the extractor simply stripped the alloy thread on the crank arms. The axle was cut on the left side and the bottom bracket removed, still attached to the spider via the right side. After a clean, the threads were chased with a standard English 1.37″ 24tpi tap. As expected, the tap offered little resistance and it was clear that the threads was too far gone to be saved. Time for plan B.

There is a type of cartridge style bottom bracket labelled “threadless”. This is somewhat misleading as they do have threads but rather than threading into the frame, they are tightened by threading together. These offer a solution to people in such a situation.

A new single chainring 42T crankset fitted along with the same chain (ultrasonically cleaned), it’s back together. All fourteen gears of the Rohloff Speedhub shift smoothly and the crank feels solid even when standing on the pedals.

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