Rear caliper piston movement

D

Duane

Member
Hi Team,
I have the rear calipers out of my TC and, after winding the pistons back in, thought I'd operate the quadrant to see how far the pistons come out. They only seem to come out about 5mm irrespective of how much ratcheting I do.
Does that sound right? I want to make sure they are working correctly before I put them back in.
 
Thanks Vern.

I thought that the more you ratcheted, the more the piston would come out, but obviously there is a limit.
 
The pad piston should come out until it runs off the end of the ratchet thread, so a lot more than 5mm. It's probably got some teeth worn off the ratchet.
 
Two motions involved. Moving the quadrant should move the piston back & forth that 5 mm. Over many movements, the piston should start to stick out further. However, it takes something like 30 strokes to get a turn on, and the thread is quite fine so a turn only extends the piston a mm or so. The piston has to be restrained for the screw to work, so if it's slowly rotating as you ratchet that indicates you're just rotating the entire assembly and not extending the screw.

Yours
Vern
 
Thanks Vern. Yes I finally clicked that I had to stop the piston turning for it to ratchet out. Seems to be working fine after disassembly and ready for refitting. Now trying to get a rebuild kit for the servo which I found full of fluid. Not readily available in New Zealand anymore so might have to be a UK order.
 
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