2 quick caliper rebuild questions

[djmcmath]

I'm rebuilding the calipers on my 3.2L Carrera, and had some confusion. The fronts were easy -- 20 degree offset, easy to work with circlips, no problems. The rears -- not so much.

Question 1 - The rebuild kit directions explain that the piston should be offset 20 degrees, unless it's the kind of piston that shouln't be offset 20 degrees, in which case it should be offset 0 degrees. They show a piston that looks kind of like the rear calipers. The Bentleys says that pistons should be offset to 20 degrees, but doesn't specifically say anything about the rears. The Pelican tech articles says 20, but only shows the fronts. Before I do the stupid thing, should my rear calipers be aligned to 20 offset or 0 offset?

Question 2 - In lieu of possessing the special tool for reinstalling those funky little metal clippy-tab things that hold the dust-boot onto the caliper, how am I supposed to get those buggers to stay in place? I'm cautious of applying too much force, as I don't want to damage the dust-boot, but I'm obviously not applying enough, or enough correctly, to get the clip to stay in place. Any thoughts on the right way to mount those clips?


TIA,

Dan

[aj88cab]

I had the same problem with the rear retaining rings, You press on one side the other side pops off, plus you think you are going to cut the rubber with the metal ring.

This is what I did.

You know those threaded PVC couplers that the P-Trap under your kitchen sink is held together with. Well if you cut the tabs off, it is exactly the right size to put over the dust boot and press it on. Position one side of the metal retaining ring in the slot then firmly apply pressure with the PVC coupler and it will snap on. I know there is probably a very expensive special tool for this, but if it works.....

As for the piston alignment I aligned both my front and back.

Good luck
Andrew

[djmcmath]

Thanks, Andrew! That's exactly the kind of quick answer I was looking for.

Dan

[qcwang]

Question1: I did the 20 degree thing for both front and back.

Question 2: I have an 83 SC and I think the rebuild kits are the same (if not forget the rest). For the dust boot retaining ring/clip I just separated the ends of the rings with my hands and gently slipped it over the dust boot. I then took a flat edge of a small screwdriver (careful not to poke the boot) and gently pressed all the way around to seat the ring. For something softer, get some Chinese take out for lunch and use the end of a wooden chopstick to press it down (make sure you eat lunch first! Brake fluid and grease flavored chopsticks will make your lunch taste bad. )

[Bill Verburg]

Understanding the reason for the o/s will answer the question.

When the pad is pushed into the rotor there is a build up of hot gases between the rotor and pad, this outgassing is more pronounced under the leading edge than the trailing edge. If no compensation were employed the pads would then be worn w/ a marked taper, less on the leading edge more on the trailing. there are several methods of compensation. On 2 opposing piston fixed calipers, the pistons are stepped so that they can impose differential pressure across the piston face to the pad, this step needs to be angled at 20&deg to be perpendicular to rotor rotation.

[djmcmath]

Thanks for the detailed answer, Bill. That makes good sense to me.