Front caliper slider boot/sleeve

[Brendan W]

What is the purpose of the rubber sleeve ( called boot on parts lists ) on the lower slider pin of the front calipers and how much should the calipers rock when you grab them?
I think someone used mineral grease here and the sleeve has swollen and pinches a little going back in.

[Crankthat]

I ripped one by pinching it while tear down inspection.
I need to replace as it keeps the grime off the pin and that leaves the action nice and smooth with the application and release of the brakes.
Helps keep them from corrosion also I would guess.
The pins are what keeps the two halves of the assembly from separating.
The part that is bolted to the forks is behind.
The main body that holds the piston and fluid is what you see and bleed in the front.
The fronts are locked into the "behind" part with the threads of the pins.
The fronts motion is kept straight (out and in) with the smooth part of the pins.
They also keep the front part of the assembly from turning.
The piston pushes on the one pad and the front part of the assembly is pulled away from the back part of assembly with this motion.
The back part of the assembly keeps it in line and centered on the disk.


The calipers shouldn't rock at all with the stock assembly.

Both the upper and lower have a boot.

Make sure there are no cracks anywhere that would cause the rocking motion.

Make sure the threads on everything are good.
I would pull all the bolts out and put them back in proper place without the assembly and check if the problem is with bolts, holes, or threads that bolts go into.

Make sure the front assembly's holes for the pins are not oval.

I think it has been two years I have not had the boot on.
Thank you for reminding me as it is the lower pin and not noticed easily.
Things are drier over here.