New disc brake squealing

[Baker7888]

as for checkg the centering of the caliper on the rotor, that can be accomplished with the use of a flat feeler gauge tool. Just open the tool up and fan the feeler leaves, then create a stack of them and insert the stack between the rotor and the pad until it only barely goes or not at all and then move to the other side and check that using the same thickness of feeler gauge leaves. Any major differentiation between the thicknesses shows up and you need to shim the caliper using thin washers to move it back or forth, depending.



Nick

Nick I have a few questions on this.

If i retract the pistons, the caliper will still slide the distance of the pin sleeve.

Because of the sliding I do not know where to take my measurement, can you help with this?

Also, about the washers. I could probably add washers between the pin sleeve and the mounting bracket. Which would pull the caliper in. But i do not see how I could use washers to push the caliper out. Could you explain?

Edited. Removed a question you had already answered

I have some new pads coming, they are better quality and have shims on the pad, which the current ones do not.

 

[78Delta88]

I had the 81 Turbo TA new, and other than Corvette, it was GM first real attempt at Rear Wheel disc. I know that 6 months in, and in the Chicago environment, I started having trouble, as well as the E-brake frozen with rust.

What the others have said about the C-Clip axles is true and can have excessive run-out and cause possible brake issues. With excess run-out the the rotor will contact the left side outer pad, and opposite side can contact the right side inner pad in a right turn. Even though brakes are not applied. It's opposite for the left hand turn. This is where you can get noise and it goes away when brakes are applied.

This is why most after-market systems and higher end cars use the 4 piston setup similar to the German/Volvo style. These cars were designed for Autobahn speeds and a GM/Ford Floating caliper system isn't the best for this.

In an event where you brake hard and then make abrupt turn, like in an emergency such as someone pulling out in front of you... It could possibly bend the rotor.

Rotor is hot due to hard braking making steel soft and malleable and quick turn change in direction while rotor makes contact with caliper that is locked in position even though not applied.

If this happens you get the noticeable ...swish-swish-swish sound, and pulsating pedal. The only fix to this is try turning them or just replace the rotors.

On the GM C-Clip axle they are very easy to do, minimal tools and doesn't change the pinon to ring gear mesh.

 

[Baker7888]

I had the 81 Turbo TA new, and other than Corvette, it was GM first real attempt at Rear Wheel disc. I know that 6 months in, and in the Chicago environment, I started having trouble, as well as the E-brake frozen with rust.

What the others have said about the C-Clip axles is true and can have excessive run-out and cause possible brake issues. With excess run-out the the rotor will contact the left side outer pad, and opposite side can contact the right side inner pad in a right turn. Even though brakes are not applied. It's opposite for the left hand turn. This is where you can get noise and it goes away when brakes are applied.

This is why most after-market systems and higher end cars use the 4 piston setup similar to the German/Volvo style. These cars were designed for Autobahn speeds and a GM/Ford Floating caliper system isn't the best for this.

In an event where you brake hard and then make abrupt turn, like in an emergency such as someone pulling out in front of you... It could possibly bend the rotor.

Rotor is hot due to hard braking making steel soft and malleable and quick turn change in direction while rotor makes contact with caliper that is locked in position even though not applied.

If this happens you get the noticeable ...swish-swish-swish sound, and pulsating pedal. The only fix to this is try turning them or just replace the rotors.

On the GM C-Clip axle they are very easy to do, minimal tools and doesn't change the pinon to ring gear mesh.

Thanks Delta. Excellent info. I may have to live with some brake noise in the rear.

By the way, they are the D50 pads. What did you mean by bending the ears in?

 

[78Delta88]

Two small tabs at top of the outer pad. The large one at bottom leave alone. When bent down slightly they will fit snug on the caliper. Keeps them from rattling.

On the inner pad there should be a spring steel clip that clips on the back of the inner pad and it will snap into the caliper piston. I usually use the spray, let it dry for about an hour and then clip on the spring steel clip.

 

[78Delta88]

Pic from AutoZone...



The two tabs on the outer pads,

Just bend down slightly with pliers/vice grips, or tap slightly with small hammer. It's all trial and error... Just make snug enough so they are tight in the caliper. You put the tabs in first then clip on the bottom of the pad. It should take slight force and with a noticable click when seated properly.

The inner pads... You see the "ears" sticking out? They fit in the grove of the caliper and they have to move to make contact and retract properly. The grove they go into has to free of rust and dirt. Use a small flat or "rat-tail" file, just small amount of high temp grease in the grove, once it's clean.

Also on the pads. If they have a straight cut 90 degree edge... You can take a flat file to the edge at a 45 degree. Not much, just a little, and this will help reduce chatter (noise) when applying brakes. You can do the same for any brake shoe for drum brakes. But don't on the small e-brake shoes.

 

[Baker7888]

Pic from AutoZone...

View attachment 222326

The two tabs on the outer pads,

Just bend down slightly with pliers/vice grips, or tap slightly with small hammer. It's all trial and error... Just make snug enough so they are tight in the caliper. You put the tabs in first then clip on the bottom of the pad. It should take slight force and with a noticable click when seated properly.

The inner pads... You see the "ears" sticking out? They fit in the grove of the caliper and they have to move to make contact and retract properly. The grove they go into has to free of rust and dirt. Use a small flat or "rat-tail" file, just small amount of high temp grease in the grove, once it's clean.

Also on the pads. If they have a straight cut 90 degree edge... You can take a flat file to the edge at a 45 degree. Not much, just a little, and this will help reduce chatter (noise) when applying brakes. You can do the same for any brake shoe for drum brakes. But don't on the small e-brake shoes.

Thanks for the help. Everything you said was very helpful and stuff that is easy to over look. I went with a set of Reysbestos pads as I have good luck with them on my truck. They have an integrated shim which the offending pads do not. Anyways I went for a decent little cruise and no noise whatsoever. I will continue to keep an eye on things but thinking it was just a crappy set of pads causing all the grief.

 

[78Delta88]

Glad things worked out.