78' Wheel/Brake Squeek

[Seeker95]

Wondering if anyone has dealt with a squeak, possibly rear passenger tire that increases in frequency with increase of speed and stops as I apply brakes. Have had new rotors ( no run out), calipers, and pads installed. Tried lubricant on back of brake pad but still there. Also it does not start squeaking until I have driven and stopped a few times. It's annoying.

 

[Rob]

Moving from the New Member Introductions forum to the C3 Tech forum...

 

[GTR1999]

The pad pin can cause this, they are sloppy in many of the pad holes or some do wear.

 

[toobroketoretire]

Trapped Air Is the Usual Cause Of Brake Pad Squealing.

Air trapped in the calipers is the usual cause of brake pad squealing as the brake pads will vibrate at a high frequency under a light brake application. So I suggest bleeding the brakes before doing anything else.

 

[Seeker95]

Air trapped in the calipers is the usual cause of brake pad squealing as the brake pads will vibrate at a high frequency under a light brake application. So I suggest bleeding the brakes before doing anything else.

Sounds good thanks for the input ill give it a try.


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[Seeker95]

The pad pin can cause this, they are sloppy in many of the pad holes or some do wear.

So its the pads sliding around the pin. How do you fix that?


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[GTR1999]

For the brakes I had like that I found the pin was out of round and replaced the pin.

I can't say I have heard air in the calipers causing that. If there was air in the system from caliper pumping, rotor runout over 005", or excessive bearing end play you would experience a spongy peddle and the dash brake light may come on if low. Did you experience any of this? It doesn't hurt bleed the brakes, I use a Motive bleeder and really like it but the old 2 man method still works if done correctly.

 

[Seeker95]

Yeah we did bleed the brakes in back after we replaced the rotors and pads along with the new pins that came with the pads. Im thinking half shaft on passenger side might be A possibility, just not sure how to check that.


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[GTR1999]

Look for rust at the u-joint caps and play in them when twisting. If you remove the shafts the joints should not bind up or have play in them. Pull a cap and look to see if there are any marks or wear on the crosses. If you go that far and the joints are old replace them with spicer solids. I burn out the old joints and use a plate to bolt the flange to so it doesn't bend.

Trim rings will squeak too, as will parking brakes.

 

[Vettehead Mikey]

So its the pads sliding around the pin. How do you fix that?

A tiny dab of high temp grease just where the pin touches the pad will help diagnose/eliminate the source.

As Gary mentioned air in the caliper makes little or no sense. If anything it would help damp any vibration.

 

[Seeker95]

Look for rust at the u-joint caps and play in them when twisting. If you remove the shafts the joints should not bind up or have play in them. Pull a cap and look to see if there are any marks or wear on the crosses. If you go that far and the joints are old replace them with spicer solids. I burn out the old joints and use a plate to bolt the flange to so it doesn't bend.

Trim rings will squeak too, as will parking brakes.

Thank you very much, have to check that out on days off! By the way trim rings are where?


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[Seeker95]

A tiny dab of high temp grease just where the pin touches the pad will help diagnose/eliminate the source.

As Gary mentioned air in the caliper makes little or no sense. If anything it would help damp any vibration.

Ok ill definitely try that as well thank you!


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[GTR1999]

The trim rings are used on stock rally wheels, if you have the aluminum slotted ones then you don't have trim rings.

Use only a dab of grease, you don't want to get any on the pad or rotor.

With these old cars there are a lot of noises if the parts are old or original. See if you can duplicate the noise when you have the car on stands BUT DO NOT put it in gear and let it run if the rear suspension is hanging down- it will bind up the u-joints and break something. I had a diff in with a blown posi case because of that.

 

[Seeker95]

The trim rings are used on stock rally wheels, if you have the aluminum slotted ones then you don't have trim rings.

Use only a dab of grease, you don't want to get any on the pad or rotor.

With these old cars there are a lot of noises if the parts are old or original. See if you can duplicate the noise when you have the car on stands BUT DO NOT put it in gear and let it run if the rear suspension is hanging down- it will bind up the u-joints and break something. I had a diff in with a blown posi case because of that.

I have the aluminum slotted wheels. Eventhough only 44k it is 38 years old so makes sense rust or just being older will make more noise...like me.

 

[toobroketoretire]

Bleed the brakes and the squeal will disappear. The squeal is caused by a high speed brake pad vibration because of a small amount of air is behind the pistons and it only happens during a light brake pedal pressure. And never remove the springs because removing them will cause faster brake pad wear.

 

[spikebot 81]

The pad pin can cause this, they are sloppy in many of the pad holes or some do wear.

Gary is correct. My car has the squeak right rear only. I used a very small dab of grease to lube the pin and the noise stopped. The lube lasted a fair amount of time but does reoccur.

 

[toobroketoretire]

Gary is correct. My car has the squeak right rear only. I used a very small dab of grease to lube the pin and the noise stopped. The lube lasted a fair amount of time but does reoccur.

It's still squeqaling because the caliper still has air in it. The original spindles and rotors were riveted together and turned and ground as an assembly and if a rotor has been replaced without replacing the spindle there will be some run out that will pump air into the caliper.

 

[GTR1999]

Gary is correct. My car has the squeak right rear only. I used a very small dab of grease to lube the pin and the noise stopped. The lube lasted a fair amount of time but does reoccur.

So now you know where the noise is. There won't be any issue leaving it but look at the pin to see if it's worn. The fit is pretty loose in the caliper and pad hole.

As Toolbroke mentioned the axles and rotors were assembled, riveted, then final turned on the axle center so the rotor surface was perpendicular to the axle center line. The result was -0- runout thru 360* rotor rotation. The 4 piston calipers float so rotor runout typically over 005" thru 360* or bearing endplay more then 003" may result in air pumping of the brake system, even though the caliper seals do not leak fluid they will draw in air into the system. The amount depends on the runout and condition of the caliper seals. It doesn't matter if the caliper is the original cast iron bore or rebuilt with SS sleeves. SS calipers addressed the issue of acidic brake fluid attacking the cast iron bore and pitting it, compromising the seal fit and leaking. Air in the system will result in various stages of failure. Starting with a spongy pedal that if left unattended will get worse and pedal failure will result. If the system loses pressure the spool in the valve plumbed from the M/C will move, activating the dash red "Brake" light. That was considered the brake safety system at the time. It does work to let you know but by that point your pedal is on the floor, maybe you will be able to pump the pedal to get some pressure to stop.
This is completely off the topic but it may help you understand the system that was used from 67-82.

To correct rotor runout I do not machine the rotors on a brake lathe since they are not going to be concentric with the axle center, you will just remove iron for nothing and there is a small window between good and discard. 035" considering both side to be exact from new to junk. Instead I tap and bolt on the rotors and shim to get the runout under 003" works like a charm. You could bolt them and machine as one like the factory did, I have done this but most are not going to have access to 13" or larger lathe and it's a lot easier to assemble the spindles without the rotor installed. Unbolting it after assembly turning then bolting it on later most likely will still have 001-002 runout, shimming just makes more sense. I have done 100's of them like that.

Ok all done, time to move on.

See ya