[jHawk104]

Greetings,

So here's what I'm dealing with on my 04 LS 4wd. About 8 months ago, I had the front suspension redone (new control arms, bushings, ball joints, etc.) as well as new brake pads. After the work was done, I started getting an ABS code right front wheel speed sensor. A few months later the D/S front brake pads are entirely worn down, and the P/S are unevenly worn (picture below). Could the two issues be related? When I brake it's doesn't pull to one side or the other.

 

[Ravalli Surfer]

Your caliper pins are either missing the internal bushings or they are worn out. It's "torque-ing".

 

[Ravalli Surfer]

That doesn't figger for the quick wear so much though.

 

[Schurkey]

The Trailblazer/Envoy series vehicles use aluminum calipers front and rear. The fronts have double pistons, the rears have single pistons--at least the ones I've looked at. Ravalli has "Cop Car" brakes which may be different.

Aluminum calipers are known for corroding behind the square-cut seal. The build-up of corrosion causes the seal to be "squished" into the piston, making the piston "sticky". The brakes still work, but the piston doesn't retract like it's supposed to. This increases brake drag. As things progress, the pistons get stiffer and stiffer until they seize in the bore, and the brakes burn the pads to nothing or the brakes quit working at all.

MOST folks would fix this by buying rebuilt calipers, which also gets you new pins 'n' bushings, fresh lube, new bleeder screws, etc.

Because I'm a cheapazz, I pull the calipers apart, clean the corrosion out of the seal grooves, polish the pistons a little, clean the scuzz out of the caliper bore and off of the square-cut seals, lube the square-cut seals and the caliper bores with brake fluid, and put 'em back together. The rears are much easier than the fronts, because dealing with two pistons is way harder than dealing with only one piston. It's not twice the work, it's like four times the work.

View attachment 58705

Wild Guess: The ABS code is not related to the rapid pad wear. I bet you find a damaged wire harness on that ABS wheel speed sensor. That, or there's rust build-up under the sensor's shim, pushing the sensor up and away from the toothed wheel in the hub.

 

[nnorton44]

The Trailblazer/Envoy series vehicles use aluminum calipers front and rear. The fronts have double pistons, the rears have single pistons--at least the ones I've looked at. Ravalli has "Cop Car" brakes which may be different.

Then in 06+ the calipers are cast iron (4.2, EXT, 5.3, SS)

 

[Ravalli Surfer]

The Trailblazer/Envoy series vehicles use aluminum calipers front and rear. The fronts have double pistons, the rears have single pistons--at least the ones I've looked at. Ravalli has "Cop Car" brakes which may be different.

Aluminum calipers are known for corroding behind the square-cut seal. The build-up of corrosion causes the seal to be "squished" into the piston, making the piston "sticky". The brakes still work, but the piston doesn't retract like it's supposed to. This increases brake drag. As things progress, the pistons get stiffer and stiffer until they seize in the bore, and the brakes burn the pads to nothing or the brakes quit working at all.

MOST folks would fix this by buying rebuilt calipers, which also gets you new pins 'n' bushings, fresh lube, new bleeder screws, etc.

Because I'm a cheapazz, I pull the calipers apart, clean the corrosion out of the seal grooves, polish the pistons a little, clean the scuzz out of the caliper bore and off of the square-cut seals, lube the square-cut seals and the caliper bores with brake fluid, and put 'em back together. The rears are much easier than the fronts, because dealing with two pistons is way harder than dealing with only one piston. It's not twice the work, it's like four times the work.

View attachment 58705

Wild Guess: The ABS code is not related to the rapid pad wear. I bet you find a damaged wire harness on that ABS wheel speed sensor. That, or there's rust build-up under the sensor's shim, pushing the sensor up and away from the toothed wheel in the hub.

Can you not buy caliper rebuild kits any more? I always rebuilt them in-house to keep the cost of complete components down by buying the kits or parts needed and the labor was pure profit.

Oh well ... that was "then" and maybe that spirit is dead now.

I shiver at reusing the original rubber parts though. The flex of the square ring is the pull back for the piston and it should be new for max effect I feel.

On dual piston calipers ... yes ... uneven pad wear from torquing was a very big problem for years and to help alleviate it, very stout sliding pins OR like the mid evolution 1980s vehicles where the calipers slid on tracks or vee-shaped grooves- was a decent design.

It took part of the oddball pad wear problems away at the cost of too much stiction generated by more places where things resisted any return to a neutral position.​

This extra stiction reduced the square ring's pull back effect, causing greater pad wear, higher heat and glazing because although the pistons would retract, the rest of the movable parts couldn't overcome the flaw in the design.​

On some vehicles, the pads would actually jangle when the piston (doing it's thing correctly, and being unhampered) retracted as designed but nothing else did ... leaving the pads free to rattle.

This is when the various flat springs and replaceable guides between the pads and/or the calipers and the caliper mounts were designed to at least keep the damned pads quiet ... and customers happy with non musical brakes.​

​

No vehicles I currently own either stayed with- or are now- using aluminum calipers.

"In the day" we had a lot of corrosion problems with them until Chrysler opted to phenolic pistons ... which is a story unto themselves.​

Stainless steel pistons and cast iron calipers seem to be an industry standard until you hit more exotic vehicles.

Since the whole TB/VOY lineup looks like another total lossleader by GM ... there very likely are calipers made from Martian Tungsten that's kissed by Angel's I guess.

Every once in a while GM tries something new and gets hammered by consumers... I submit the following

Corvair
Vega
Buick GS
Opel Manta "Baby Corvette"
Cadillac 4-6-8
Pontiac Fiero
Toronado/ Eldorado FWD
4.3/5.7 DX & D diesel vehicles
3.8 L Odd-Fire V6
3.8 L Even Fire V6
First year GM Vortec SBC with wrong head angle & short valve guides
The Atlas Engine series of L4, L5 & L6 ... which is a solidly good design, but needed a few more years to debug a bit more..
There are others.

​

 

[NJTB04]

Can you not buy caliper rebuild kits any more? I always rebuilt them in-school to keep the cost of complete components down buying the kits or parts needed and the labor was pure profit.

Oh well ... that was "tgen" and maybe that spirit is dead now.

I shiver at reusing the original rubber parts though. The flex of the square ring is the pull back for the piston and it should be new for max effect I feel.

On dual piston calipers ... yes ... uneven pad wear from torquing was a very big problem for years and to help alleviate it, very stout sliding pins OR like the mid evolution 1980s vehicles where the calipers slid on tracks or vee-shaped grooves- was a decent design.

It took part of the oddball pad wear problems away at the cost of too much stiction generated by more places where things resisted any return to a neutral position.​

This extra stiction reduced the square ring's pull back effect, causing greater pad wear, higher heat and glazing because although the pistons would retract, the rest of the movable parts couldn't overcome the flaw in the design.​

On some vehicles, the pads would actually jangle when the piston (doing it's thing correctly, and being unhampered) retracted as designed but nothing else did ... leaving the pads free to rattle.

This is when the various flat springs and replaceable guides between the calipers and the caliper mounts were designed to at least keep the damned pads quiet ... and customers happy with non musical brakes.​

​

No vehicles I currently own either stayed with- or are now- using aluminum calipers. "In the day" we had a lot of corrosion problems with them until Chrysler opted to phenolic pistons ... which are a story unto themselves.

Stainless steel pistons and cast iron calipers seem to be an industry standard until you hit more exotic vehicles.

Since the whole TB/VOY lineup looks like another total lossleader by GM ... there very likely are calipers made from Martian Tungsten that's kissed by Angel's I guess.

Every once in a while GM tries something new and gets hammered by consumers... I submit the following

Corvair
Vega
Buick GS
Opel Manta "Baby Corvette"
Cadillac 4-6-8
Pontiac Fiero
Toronado/ Eldorado FWD
4.3/5.7 DX & D diesel vehicles
3.8 L Odd-Fire V6
3.8 L Even Fire V6
First year GM Vortec SBC with wrong head angle & short valve guides
The Atlas Engine series of L4, L5 & L6 ... which is a solidly good design, but needed a few more years to debug a bit more..
There are others.

​

Don't forget the X bodies.

 

[Ravalli Surfer]

Don't forget the X bodies.

The "K car" of GM, YUP.

Going home, no wifi. Will take 4-5 hours.

 

[Schurkey]

I have had beyond excellent "luck" re-using the original rubber seals in my calipers. I've re-used the seals starting with my Honda motorcycle (aluminum calipers, pistons seized) more than once, GM iron calipers on pickups and cars, and these Trailblazer aluminum calipers.

Obviously, I inspect the rubber for cracking or any other signs of deterioration. I figure, those seals weren't giving me any problems before...it was the metal of the caliper body that was the real problem...so they're not likely to give me any problems after I fix the corrosion in the caliper, and clean out the crusty deposits and muck in the caliper bore, piston, and rubber seals.

That said...I've never done this on a "customer" car. Only my own vehicles.

I haven't even tried to buy caliper rebuild kits, or wheel cylinder rebuild kits in decades. The kits cost as much as "rebuilt" or sometimes even "new" parts; and you don't get a warranty with the rebuild kits.

 

[Ravalli Surfer]

I have had beyond excellent "luck" re-using the original rubber seals in my calipers. I've re-used the seals starting with my Honda motorcycle (aluminum calipers, pistons seized) more than once, GM iron calipers on pickups and cars, and these Trailblazer aluminum calipers.

Obviously, I inspect the rubber for cracking or any other signs of deterioration. I figure, those seals weren't giving me any problems before...it was the metal of the caliper body that was the real problem...so they're not likely to give me any problems after I fix the corrosion in the caliper, and clean out the crusty deposits and muck in the caliper bore, piston, and rubber seals.

That said...I've never done this on a "customer" car. Only my own vehicles.

I haven't even tried to buy caliper rebuild kits, or wheel cylinder rebuild kits in decades. The kits cost as much as "rebuilt" or sometimes even "new" parts; and you don't get a warranty with the rebuild kits.

Sounds about right --- discouraging the labor in the shop and forcing you to buy instead of the "liability" - that in reality, doesn't actually exist if you do a good job.