Archived new pads & rotors, can't get caliper back on

[CharlieFoxtrot]

96 2500 2wd CTD, confirmed 8800 GVW on door sticker.



Another member had a similar problem and I posted in his thread, but my truck is down so I'm here in 911. The other poster ended up having the wrong pads, but that doesn't seem to be my problem.



I got Napa Ultra Premium pads and Premium rotors. The pads are just a hair too tight to go over the rotor. The caliper and new pads fit fine over my old rotor. Pad part # is UP7339SD on the box, the correct listing for 8800 GVW. There weren't anyone's greasy fingerprints on the box, so I assume the pads in the box are what they should be.



Rotors are the same for 8800 and 7500 GVW. Minimum thickness spec stamped on the rotor is the same for old & new, so pretty sure there's no parts problem there.



The caliper is compressed fully; didn't compress any further with bleeder loose. However, the piston is noticeably not flush with the caliper body - like 1/8"+ out. Could it have deposits inside or other problem that causes it to not retract fully? I bent my c-clamp trying to push it in further! FWIW, looking at calipers on NapaOnline, the pistons in new ones appear to also not sit flush with the body.



WTF? #@$%!



BTW, I've been working on cars for 25 years and have replaced more brake pads than I could possibly count, so I hope it's not user error... .





thanks all



kevin

 

[Sticks]

By how much are they not fitting? It might just be an alignment issue - pads not parallel while trying to slide down the rotor.

 

[CharlieFoxtrot]

I'll measure the gap between pads when I take it apart again tomorrow, but it's maybe 1/16". I triple-checked that they were in straight. In fact, when I try real hard to get the caliper on, the pads will cock just a bit, creating enough space that they will barely start to go on, but then of course they won't go any further.



I'm going to NAPA tomorrow and compare my pads with the 7500GVW. The other poster with this problem, Surfbeetle, https://www.turbodieselregister.com/forums/2nd-generation-ram-forum-no-engine-transmission-discussions/223374-front-brakes-my-95-2500-a.html#post2163786 says he used the 7500 pads and they work fine; the part # is the same as his previous pads, but the catalog listings swapped the 7500# and 8800# applications. It'd be pretty weird if that's my problem too, since his problem happened at Pep Boys!



thanks

kevin

 

[BDaugherty]

To me it sounds like you may have got the pistons cocked a little. If you don't press them in squarely, they will wedge in the bores and won't move. Try pressing the brakes gently to puch the pistons back out just a little and then use one of the cheap screw operated caliper compressors from the parts store. You should be able to pick one up for 5-8 dollars. Personally, I use a big honkin' set of channel-locks to push the pistons back in.

 

[CharlieFoxtrot]

That's an interesting idea, though I actually used the big honkin channel locks first, then went to the C-clamp. I think I also have one of those pad spreader tools. Will try it.



thanks!

kevin

 

[dknoch]

If you haven't, run a couple lug nuts down on the rotor to help it line up and not move. This may help it slide over the rotor. Has worked for me in the past. Good Luck!

 

[CharlieFoxtrot]

Mine's 2wd, so the rotor is integral with the hub. No need to worry about it moving around like on your 4wd.



Thanks!

kevin

 

[Sticks]

Even some 4wd trucks were married, it was a crap shoot if you got floating rotors or not.

Other than the suggestions above, and verification of parts (more common than you think to get part A in box B from NAPA). I can't think of anything else.

 

[GAmes]

Did you compress the piston by opening the bleeder screw? OOps, reread your thread. FWIW, the pistons on mine will compress to flush. You may need some new calipers.

 

[CharlieFoxtrot]

Thanks, all! Truck is back on the road.



Calipers at NAPA had pistons no more retracted than mine were, so no caliper problem. 7500 pads were thinner, and I got a set and put them in. I did have to bend the spring clip on the back of the inside pad a bit so it grabbed the piston fully. Because of that, I'm not convinced this was the _correct_ solution to my problem, but if it isn't, I don't know what is.



Thanks again!



kevin