More on rear disk conversion

I've still got issues with the rear brakes, with the left hand side dragging and an ineffective handbrake. A lot of problems can be diagnosed with careful visual inspection, so that's what I did. I thought disk runout might affect the self-adjusting mechanism, so I checked it with a dial gauge. It measured 0.2mm max at the disk edge, and this seems to be caused by the hub face being slightly out of true.

The handbrake return springs were bent, so I've ordered a new pair. It turns out that the modified levers stop the mechanisms from returning to their 'off' positions, so a little modification with a hacksaw is in the pipeline.


Hi Oliver,

When my conversion was done, I had similar problems with both new Sierra calipers binding on. It turned out to be the pair of internal spring washers behind each piston, not being strong enough. These prevent the piston being wound up tight onto the disc when the handbrake is applied. They retain enough movement in the piston to allow them to return..if you see what I mean.

Both sides of mine were swapped over for pairs from old calipers.. no more binding. They are like a pair of small washers back to back, but with a twist/bevel in them to give them a bit of spring.

BECs Rule !