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Dragging rear disc brakes

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Old 06-25-2011, 11:28 PM   #1
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Dragging rear disc brakes

Just purchased a 2000 2wd blazer. Just bought all new (minus calipers) rear brakes for it.

The brake shop that did them before used the wrong pads, they were too big and wouldn't float like they should. They were dragging for some time i believe from the amount of brake dust that was built up on the rear hatch. This dragging caused some serious heat.

So I went through with all new rotors, caliper brackets, pins, ect. Got it put back together today and it is doing the same thing. Everything went together really good. Pads float awesome in the new caliper brackets and the rear end spun fine when on jacks. Got back from a test drive to see the new rotors starting to change colors from the brakes dragging still. I sprayed the rotors lightly with some brake clean when i got back and it immediately evaporated, so i know they were pretty hot.

Anyone got and ideas? I was thinking all the heat from the original job might have wreaked the calipers? Or i was thinking a funky residual pressure valve. Any input would be appreciated.
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Old 06-26-2011, 10:20 AM   #2
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Re: Dragging rear disc brakes

i had a hell of time when i went to 98+ discs on mine. The pad kept hanging up in the slides. On jack stands everything floated great, and worked fine. As soon as you hit the brakes at any speed the pad got stupid and hung up tilting the top of the pad towards the disc. I got caliper warrentied thinking that was the problem at first. As far as i could tell it was the little anti rattle clips or whatever they are called tweaking the pad. I spent some time with a dremel getting them sit better in the caliper and that seemed to help a lot.


edit: as far as the prop valve goes, mine is gutted, so that wasnt the case for me
Old 06-26-2011, 03:29 PM   #3
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Re: Dragging rear disc brakes

Well got it all torn apart. Not finding anything unusual. Pads are sliding fine, calipers are floating on the pins just fine too. Calipers compress together fine when tightened with a big c clamp. Don't have to ream on the or anything to get them to break lose.

But the problem of dragging is still existing, Pretty much re-assembled the whole rear brakes like yesterday and threw wheels on. Got in and pumped the brakes a couple times. When back to see if rear wheels would spin while still in the air, they do but it requires some serious torquing on them. More then a normal brake drag.

It has to be some sort of hydraulic problem, not a mechanical problem.

I tried locating the residual pressure valve but couldn't find it. I do believe that the s-series with rear discs had these somewhere on them.

Could also be a messed up proportioning valve or possibly a bad ABS unit.
Old 06-26-2011, 03:37 PM   #4
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Re: Dragging rear disc brakes

I have the same issue with the rear discs on the Sonoma, and I've heard tons of different opinions on both sides of why it's doing it, but I have yet to figure it out

Exact same issue as you tho. And from what I've heard Blazers with factory discs SHOULD NOT have an RPV. Only trucks or Blazers with rear drums had them, as they are used to keep the pads out at the drums, overcoming the springs
Old 06-26-2011, 05:35 PM   #5
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Re: Dragging rear disc brakes

Hmm.

Im thinking the issue is a ABS one. I know your truck still has abs on it too brent. Thinking of gutting that shit and throwing in a standard disc/disc proportioning valve. That would eliminate every option minus a pinched line. From what i have read, the abs unit in the newer trucks also operates as the proportioning valve.

Not looking forward to re-bleeding everything tho.
Old 06-26-2011, 06:01 PM   #6
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Re: Dragging rear disc brakes

you guys.. the rear brakes are supposed to drag a bit. It keeps the rotor surface clean. That is the way they are designed. They don't float, they drag. I heard that from SSBC's public relations guy not more than a month ago.
Old 06-26-2011, 06:24 PM   #7
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Re: Dragging rear disc brakes

i'm going to have to say brake line on this one. look for a kink in the line, it's likely causing the problems if there is one. if not, well... i'm not quite sure.
Old 06-26-2011, 06:35 PM   #8
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Re: Dragging rear disc brakes

it took me for ever to get mine driveable b/c of a horrible rear passenger side drag, as in it was literally clamping so hard i couldnt spin the wheel by hand. I took it a part a 100 times and checked everything. All new lines, new master, every rear brake part was brand new too. Good luck, i chased mine for a long time and then for the first 100 miles are my right rear brake was still acting funny, and grabbing every now and again but is doing perfect now. If the calipers are new id suggest warranting them and trying a new pair. After i did that and messed with how the clips sit in the caliper mine was a lot better
Old 06-27-2011, 02:58 AM   #9
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Re: Dragging rear disc brakes

Quote: Originally Posted by n8rsk8r
you guys.. the rear brakes are supposed to drag a bit. It keeps the rotor surface clean. That is the way they are designed. They don't float, they drag. I heard that from SSBC's public relations guy not more than a month ago.
Not as much as these are man. You can barley turn them over by hand with a wheel on the rear end while up in the air. Plus the rotors are turning blue from them dragging as much as they are.

Calipers are still the originals. They function fine though. You can compress them back together fine with a giant c-clamp.

As for the pinched line, im not really seeing anything that looks to be pinched. I was under it today changing the fuel filter and didn't see anything unusual.
Old 06-27-2011, 03:09 AM   #10
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Re: Dragging rear disc brakes

not sure what else you could do then other than new calipers..
Old 06-27-2011, 03:57 AM   #11
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Re: Dragging rear disc brakes

Can you back the piston out some? Is there a brand that has more pad than others? Or a different part # or what?
Old 06-27-2011, 09:15 AM   #12
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Re: Dragging rear disc brakes

Quote: Originally Posted by GET_LOW
As for the pinched line, im not really seeing anything that looks to be pinched. I was under it today changing the fuel filter and didn't see anything unusual.
How about blowing compressed air through the line? My rear brakes wouldn't bleed properly so I disconnected it at the front prop valve and at the back near the axle, blew air through the line, reassembled, and everything worked great. Something must have been clogging it.
Old 06-27-2011, 05:24 PM   #13
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Re: Dragging rear disc brakes

Quote: Originally Posted by n8rsk8r
Can you back the piston out some? Is there a brand that has more pad than others? Or a different part # or what?
This might be a contributing factor. The pads i bought are pretty thick (not like way thick but have some decent thickness for rear brake pads). The caliper has to be compressed by c-clamp in order to get them on. There is about a 1/4 or so of compression from the pads engaged to caliper fully collapsed. Im thinking that the pad thickness may be causing the rear calipers to be set too far out of there designed operating range.

Mike, im thinking re-bleeding or totally blowing the lines out wouldn't be a bad idea. Im just worried cause of the horror stories i have heard about trying to bleed a abs brake system.
Old 06-27-2011, 05:57 PM   #14
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Re: Dragging rear disc brakes

**** the abs for one. and two just plug the brake lines in the back, you only need front brakes. thats what i did on my truck.
Old 07-01-2011, 06:52 PM   #15
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Re: Dragging rear disc brakes

I have the same problem on my s-10 2002 rear disc "blazer swap". The reason of the drag... drum axle is larger so you will need a 1/4 spacer on brake backplate four bolts. Thats why the pad is frictioning the rotor, so after 200 miles it will losen up. I see on ebay the spacer for this problem. Nex time that i will have to change my pads i will take the calipers for cut them at machinshop about 1/8...
Old 07-01-2011, 08:21 PM   #16
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Re: Dragging rear disc brakes

my 02 blazer when i bought it told the dealership both rear brakes are dragging and went thru a big ordeal with them about that, they tried greasing the slides but didnt do anything.

they ended up replacing both rear calipers and rubber hoses and that fixed it. possibly your hoses are collapsed? looks like a shitty design to me having the hose in a u shape like that...
Old 07-02-2011, 11:19 PM   #17
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Re: Dragging rear disc brakes

Bad calipers are a known issue on the Blazer/Jimmy rear discs. I had to replace both of them on my 98 Jimmy after screwing around with new pads then new rotors and pads. Kept dragging. Replaced both calipers and no issues. Had the same issue with the right rear caliper on my 03 Blazer. Just because you can compress them doesn't mean they are working as they should. They get a little dirt and junk in them and they wont release like they should. Just get a new caliper. The caliper only is around $45 exchanged at parts stores. The ones I got for my Jimmy were twice as much or more because I got the whole caliper and bracket. I didn't know you could only get the caliper at that time.
Old 07-05-2011, 12:12 PM   #18
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Re: Dragging rear disc brakes

Mine seems to have somewhat fixed itself as of recently. It comes and goes though. And thinking back to when I rebuilt the axle I replaced just one of the calipers because of a stuck bleeder screw (they both compressed just fine) and I believe that it was my passenger side caliper, hence why I'm probably having the issues with the drivers side caliper. Although, after burning through an entire set of pads on the drivers side the caliper ended up popping the piston completely out and then bleeding a bit of fluid past the piston, but after reassembling the caliper with new pads I haven't noticed the dragging issue so much anymore. When I do my LS1 Fbody brake swap I will probably replace that caliper also, and I have new hoses already for them so those will get put on at that time as well, in addition to a full re-bleed
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