Akcelr8 N VA

I'm replacing my CarboTech XP10s in the rear of my '93. I've done this at least 8 times over the last two years and never had a problem. This is how I did it: I removed the caliper bolt, swung the caliper away from the rotor and removed the old pads. Opened the bleeder valve and pushed the piston all the way in, put the new pads in and the caliper won't clear the new pads (it won't expand wide enough) . I then removed the parking brake cable (PIA, by the way) and saw no change to the distance between the piston and the outer caliper facing, and it still won't clear. It's the same clearance problem on both rear calipers. I thought maybe the new pads were "out of spec" so I put in another new set of street pads for comparison and they also won't fit. The lever that pushes the piston assembly for the parking brake is fully retracted (it's against the stop) so no further retraction can occur that I can see. Anyone run into this problem before???

(I also posted this on the C4 section but haven't got any responses yet)

spazegun2213

got a grinder you can take to the pads? I've never heard of this, and the fact that you've tried 2 different sets of pads says that something is wrong.... but i have no idea.

Solo2GS

I often use the old pad along with a large C-clamp to make sure the caliper piston is all the way compressed. Often by hand I cannot compress them in all the way. Perhaps they are not in all the way?

Kanmer

Ralph,

Make sure that the caliper didn't slide on the pins. I have had similar issues but after sliding it on the pins it fit. Kind of a bonehead thing but hey, if it works...

You and me doing the same thing right about now. Prepping for this weekend. If you want more practice you can come down and help me with Nancy's C4.

Bob

Akcelr8 N VA

Yep, that's the plan for the short term so I can run this weekend at VIR. I sure wish I could find out what the cause is though!!! See you this weekend.

Akcelr8 N VA

Solo - the pistons are fully compressed using both a c clamp and large channel locks. BTW, this problem is identical on both rear calipers!! It appears that the assembly that holds the piston is not fully retracted because of the parking brake lever (mounted on the caliper), which is disconnected from the parking brake cable. The lever, however, is against its stops and can't retract any further and I see no adjustment for this.

Bob, I've taken the caliper completely off the caliper bracket and tried to "slip it over" the pads with no luck!!

Bob, I got a better idea, why don't you drive up to NoVA and fix this for me????

abc 123

Post up a picture, if you can.

Akcelr8 N VA

If I don't figure this out tonight, I'll post a picture. If I do figure it out, I'll post the cause and solution!!

96GS#007

The rear pads are inboard/outboard specific. Swap them around. To tell them apart, look at the backing plate. One will have two raised bumps, the other will not.

Akcelr8 N VA

You're correct, however the Carbotech pads I have this time, don't have any of the tabs on the backing plates so in this case that's not a factor. Thanks for the input.

Kanmer

Ralph, you know I hate NoVa. Why would I drive up there on purpose?
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If you don't have it fixed by tomorrow I will come up if you need a hand. Let me know so I can get the other car prepped tonight.

Bob

94ZR1#444

Ralph, sorry to hear about the pads but I have been in the same place you are. I had to send the pads back and get a replacment set. The 4th word of your post says it all. Steamy POS comes to mind.

See ya Thursday.

larryfs

release the parking brake
the bottom slide pin needs to move freely in and out, so you can "center" the caliper over the rotor.

I also use of those $10 spreaders on the rear calipers. open the bleeder, and crank it in fully.

abc 123

He says the parking brake cable is disconnected.

larryfs

it was a joke.... but you never know.

last year I blew out a caliper accidently, by pressing on the brake pedal when the caliper was off the car. opps.

the blur

if you changed rotors, and they gave you C5 rear rotors instead, they are thicker than C4 rotors.

Akcelr8 N VA

Bob, I wouldn't force anyone to come up to NoVA!!! Seriously though, if you have a used set of rear pads that I could use, please bring them to VIR. We (Mike Sarver, Rick, and Joe Malo a GM Mechanic) found that the piston is indeed fully retracted so the only conclusion is that either something mechanical is in the bottom of the cylinder or the caliper housing has warped, or BOTH sets of new pads we tried were out of spec. The confusing thing is that it is the same situation for BOTH right and left calipers! Anyway, tonight I'm shaving a couple of milimeters off the pads (hate to do it!) so I have something for the weekend. If I screw that up, I may need to use your old C4 pads as a backup.

See you this weekend

Akcelr8 N VA

Hey Mark, you're quite right about the 4th word, their quality control has been for sheet lately! See ya Thursday, stop by for a cool one!

Akcelr8 N VA

Nope same C4 rotors that I pulled the old pads from. They were XP10 pads as well. See the post to Bob for my conclusions. Unfortunately, I still don't have a definitive answer, but I'm ordering two new calipers, I'll mic the difference and that should give me a clue. Thanks for the input!

Kanmer

Ralph,

Unfortunately Nancy needs rear pads also. She needs front rotors as well. The HP+ pads she was using were not quite up to the task and tore her rotors up. I am on my way out to pick that stuff up now. So the long ofthe short of it is I don't have any C4 rear pads but if you need a hand at the track I am more than happy to lend a hand...or at least supervise. I can do things like drink beer and say "make sure that bolt is tight".

New calipers? I am not sure thats the answer. If the caliper was warped or stretched your old pads would be tapered and there would not be a fitment issue. as a matter of fact I would think it would be the opposite. You would run out of travel before pad. I will call CDOC and make sure they have a couple of sets of rear C4 Hawk HT10's. Not a bad pad for the rear and we can try those. Other than that all you can so is shave a little of the pads you have for use now.

Bob