Shims or no shims??

[gtblast]

I am rebuilding the front brakes on my 70GT and I am trying to decide if I want to put these crusty old shims or spacer plates back in or leave them out. From what I have read, they apparently are there to reduce noise or squeal. I have done many disc brake jobs over the years and all the cars I can remember never had any shims, and they all worked fine without them. So why did the GT need shims? I am thinking it should work fine with no shims and some anti-squeal goop between the piston and the pad. Any insight would be greatly appreciated.
Fred

[West Coast GT]

Without making a recommendation one way or the other, here is what I've done, and I have not overshot any tight turns or sailed through stop signs/lights.

The backing plates are a pain in the ass to deal with. But I have retained them. I coat the back of the brake pad and the mated side of the shim/plate/whatever its called with a thin layer of anti-squeal goop. Let it set up for several minutes. Then slap them together. This helps hold the shim to the brake pad while its being wriggled back into place.

I agree with your statements, but have continued to use them until I find out why I shouldn't.

[Dennis Texas]

I'm not sure which part you are talking about if it is the sheet metal plate that fits between the piston in the caliper and the actual brake pad, I had the same question then I noticed it has a couple of indentions apparently to not allow the piston to roll around and keep it in line. I sandblasted mine painted put them back on since I had them but it would of been a lot easier not to have to deal with them. I don't know why the piston in the caliper would roll around or if it did what would it hurt but it cost extra to put them there so there must be a reason.

[namba209]

The brake squeal is nothing more than a high intensity, (read this as rapid cyclic) vibration between the piston and pad or the pad and the disc. The reason for the plates is to dampen out the vibrations. They are thin spring steel and are there to keep the pads and disc in alignment to stop the vibes. As long as the pads and disc are alignment, that is, no angular difference, both on the same plane, there wil be no brake squeal, and the shims wont come in to play. HTH.

[hrcollinsjr]

Originally Posted by Dennis Texas ... then I noticed it has a couple of indentions apparently to not allow the piston to roll around and keep it in line.

The '75 calipers are larger but use the same size pistons. The '75 pistons don't have the flats machined into the brake pad side of them.

Harold

[gtblast]

I have rebuilt calipers and replaced pads, etc. on a lot of GM vehicles. None of them had anything that would keep the piston from rotating. My guess is, that the pistons would not rotate anyway. So, I do not think that piston rotation is a concern. I understand the idea behind the steel shims reducing the squeal, but again, I have not seen this needed on any other vehicle. I am glad to see what others have done and that others have had the same thoughts I have. Thanks for your input.

[wrench459]

All noise comes from vibrations.
And since you'll never find a perfectly true rotor or pads thats when the shims come into play.
IMOA the pad material is organic in most cases (read asbestos) you don't need the shims.
The semi-metallic on the other hand needs some help either with shims or some cutting of the leading and trailing edges of the pad and/or a deep center cut in the pad.
All to keep the noise level down....the number one comeback when doing a brake job in my line of work. Bottom line keep the shims.

[Dennis Texas]

Originally Posted by wrench459 IMOA the pad material is organic in most cases (read asbestos) you don't need the shims. .

asbestos? I thought you were talking about some of the original pads, I was under the mistaken impression that all replacement pads were not asbestos. Found the following and I was surprised.

found the following at:

Asbestos Brake Dust Still A Hazard

Though asbestos brake linings have been mostly phased out, contrary to popular misconception they have not disappeared altogether. According to one original equipment brake supplier, Ford was still using asbestos linings as recently as 1993 on the Crown Victoria to cure a brake noise problem. The same supplier also said asbestos linings are still used on some high end import vehicles such as Land Rover because of their good braking characteristics. What's more, asbestos linings are still readily available in the aftermarket.

Though asbestos linings were one used on virtually all vehicles, the arrival of front-wheel drive in the 1980s required semi-metallic front disc brake pads that could withstand higher operating temperatures. But the vehicle manufacturers continued to use asbestos linings on the rear brakes as well as the front brakes on most rear-wheel drive cars and trucks. Why? Because asbestos was and still is an excellent fiber for brake linings. It offers good strength, temperature and chemical resistance, and is cheap compared to other materials that are used for the same purpose. But the physical properties that make asbestos such a good fiber also make it a hazardous substance.

Asbestos fibers are long, thin and extremely small. Exposed fibers easily shred into thin needle like strands that can drift in the air and be inhaled. The size of the fibers are such that they are not easily filtered out by the mucus linings in the nose and lungs. Hence, the fibers lodge deep in the lungs where their sharp needle like presence becomes a source of constant irritation. To make matters worse, the human body cannot rid itself of these fibers because they are impervious to biochemical assault. So over time, exposure to asbestos dust may result in lung disease or cancer.

The asbestos hazard is associated primarily with those who work in the asbestos handling and processing industries. But once the asbestos fibers are encapsulated in other materials, they pose little danger to workers in brake, clutch or gasket manufacturing plants.

There is a danger, however, to brake technicians because of the dust that is generated as brakes wear. As the linings wear, asbestos fibers are exposed and released as dust into the air. Some of the dust clings to brake parts and some of it is blown away. If a technician uses an air hose to blow out a brake drum or to blow dust off brake parts to "clean" them, the only thing he�ll succeed in doing is blowing billions of asbestos fibers into the shop environment. This will expose not only the technician himself to dangerous concentrations of asbestos fibers, but everybody else in the shop, too.

So to make a long story short, asbestos is still with us. Since there is no way to know if a vehicle has asbestos brake linings or not, it is wise to treat every vehicle as though it might have asbestos linings. And even if a vehicle does not have asbestos linings, there are still concerns that other fibers used in NAO linings may pose the same long term health risks as asbestos!

Thank you for bringing that up, I was aware of the dust when changing out old original pads and linings and I clean most of my parts in a varsal bath. Wondering how much has carried over onto other parts cleaned in that bath.
Need to be more careful I guess.

[gtblast]

Dennis,

Thanks for reminding us all about the hazards of asbestos and brake dust. Almost 40 years ago I got my first mechanic's job servicing a fleet of trucks for a local electrical contactor. I did a lot of brake jobs, and the full time mechanic there would just take the air hose and blow the dust out of the brakes. It is a wonder I have lived this long!!

I am very careful when I do brake jobs and you posted a great reminder that we all should be. I think much of the asbestos has been phased out, but it is still around and any brake dust is a hazard. Thanks for the reminder.

[wrench459]

Originally Posted by gtblast Dennis, Thanks for reminding us all about the hazards of asbestos and brake dust. Almost 40 years ago I got my first mechanic's job servicing a fleet of trucks for a local electrical contactor. I did a lot of brake jobs, and the full time mechanic there would just take the air hose and blow the dust out of the brakes. It is a wonder I have lived this long!! I am very careful when I do brake jobs and you posted a great reminder that we all should be. I think much of the asbestos has been phased out, but it is still around and any brake dust is a hazard. Thanks for the reminder.

The bad thing about brake dust or clutch is that it don't effect the older generation as much as it is a killer with our sons and daughters.
It just drives me nuts thinking about after an hard day at work and coming home to get a big hug from my son and planting asbestos in his young undeveloped lungs.

[hrcollinsjr]

Originally Posted by wrench459 The bad thing about brake dust or clutch is that it don't effect the older generation as much as it is a killer with our sons and daughters. It just drives me nuts thinking about after an hard day at work and coming home to get a big hug from my son and planting asbestos in his young undeveloped lungs.

My friend since age 5 lost both parents a few years ago to asbestosis. Everyone but him in his family is/were steamfitters and exposed to asbestos. The mom supposedly got it from washing the work clothes. She passed away before his father, both asbestosis. One brother has already passed away and a second one isn't to far behind. Asbestos was probably a contributing factor for my Dad also as he working where they used it a lot in building HVAC systems.

BAD STUFF. I've shown students how to do brake jobs and turned my back and heard the air hose where they were blowing the brake dust off. The ALWAYS get a long lecture. It's the ones that "know" what they are doing that pull that stunt.

Harold

[blancojp]

Shims might be a pain to deal with but they always come through for me.....