What causes glazed brake linings? UPDATE

Pilotdave

Pilotdave

Well-known member
I'm chasing squealing front brake issues in our Tudor. Recently I found the right front linings were glazed, so I sanded them and found that the squealing went away. Now it has returned - I'm betting that I'll find some glaze on the linings when I pull the drum.

So to my question! What causes linings to glaze?

Thanks much!
Dave

See #28.
 
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Re: What causes glazed brake linings?

Thanks, Brent. Can you explain how those conditions cause glaze? Would over-heated brakes cause glazing?

Thanks again.
Dave
 
Re: What causes glazed brake linings?

billwill, that sounds like glazing being caused by overheating the linings due to constant contact with the drum - yes?
 
Re: What causes glazed brake linings?

adjusted to tight
shoes not returning completely
loose bearings // backing plates
out of round drums
driver error riding the brakes
 
Re: What causes glazed brake linings?

I don't see it printed in the instruction sheet these days, but years ago it was stated to brake easy during the first 1000 miles to seat the brakes. It was stated that hard braking especially during the first thousand miles causes grooved linings. And, I would imaging it could also caused glazed linings and squealing brakes. Also check all of what Mitch just listed.
 
Re: What causes glazed brake linings?

A light sanding of the inside of the drum to get a clean/fresh braking surface probably won't hurt either.
 
Re: What causes glazed brake linings?

Pilotdave said:
Thanks, Brent. Can you explain how those conditions cause glaze? Would over-heated brakes cause glazing?

Thanks again.
Dave
Click to expand...

Yes, but the key that everyone else is saying is just as you suspect. It is the heat. A loose lining does not dissipate the heat through the lining into the shoe. Also, a loose lining with have 'high spots' that will contact first, --and stay contacted longest. Those small areas will overheat first. That starts the glazing process, which a glazed shoes does not have the surface friction so the surrounding areas need to take up the additional stopping force ...but they become overworked and become glazed too. I'm sure you can see a pattern here where it just keep escalating until the majority of the shoe is glazed.
 
Re: What causes glazed brake linings?

Not what caused them, but a solution from the 50's when I was a mechanic: just take a rasp and rough them up a bit.
 
Re: What causes glazed brake linings?

Thanks for these suggestions. I had to pause in the middle of typing the post below, and several of you added posts while I was (literally) "out to lunch". Thanks a lot for the input and information!

I've been trying to not "lead the witness" here too much, but let me complete the story.

1. I removed the glaze on rf brake shoes and did a test run or two with no brake squeal. But rf drum was really hot. Now after 15 miles or so the squeal is coming back.
2. I've done a short (about 3/4 mile) run without applying any brake - all four drums were cool.
3. Then I did a test run with several stops - rf was very hot.
4. In the middle of the test runs I thought I saw glazing coming back on the rf drum.

So I'm thinking the over-heating might lead to the glazing which then causes brake squeal. Could be that the shoes are adjusted too tight, though the drum turns freely with the brakes not applied - just a slight scuff at one point in a revolution. So I'm asking myself whether the short springs (one or both) may be a little weak, allowing the shoe(s) to rub against the drum a bit once the brakes have been applied.

So maybe I sand off the glaze, chase the high spot AND replace the springs. After checking the backing plate and bearing tightness.

I'm happy to hear any ideas and opinions!
Dave
 
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Re: What causes glazed brake linings?

Dave, you & I had some private conversations awhile back and I thought you replaced the drums with new cast iron drums and you also installed the new brake shoes that had the new linings already installed. Is this them??
 
Re: What causes glazed brake linings?

Even with "perfect" braking systems, some glazing is "normal"!
Minerva's brakes made noises. I removed ALL the drums & with an acid brush & some Nissan Disc Brake Lube, I lubed ALL, yes, ALL of the metal to metal contact points in ALL 4 brakes! Noises GONE! I didn't even sand the drums or shoes.
Sometimes, metal to metal contact areas act like a "musical" instrument & give high frequency vibrations a place to "sound off"! The lubricant eliminates that! Sorta like, if you greased the HORSEHAIR on yo' Bow, then yo' FIDDLE WOULD BE SILENT!!
All brake contact lubricants are NOT equal!! After years of fighting brake squeels on drum & disc brakes, I found that the Nissan Disc Brake Lube is the best!! It'll cost you an ARM & a LEG to buy a bottle from the DEALER, but it will last FOREVER! They supply a small plastic squeeze tube of it with their new brake pads.
Apply it to ALL shinny, metal to metal contact areas, it'll last virtually "FOREVER"! You DON'T have to "re-do" it every 17 weeks!!
Bill W.
 
Re: What causes glazed brake linings?

I think Bill is possibly right about high frequency vibration making the sound. I have this problem on two A's that have the original-type soft linings and cast drums. On a third A with those same linings but with original steel drums, I never hear a squeal.

Having done the sanding of linings as well as the drums and not lasting, I Googled "brake squeal". A number of suggestions came up. One made reference to frequency vibration and said that was why some cars made in the 1950's, etc. had a spring installed around the drum (at the factory). I do remember seeing that but not which car and it looked similar to an old screen door spring. Also, mentioned was thick rubber and other materials wrapped around the drum to absorb vibrations. Couldn't find an adequate spring so cut and re-glued a wheel rubber band used for protecting the inner tube. Just have not tried it and it may be too thin. Some day................
 
Re: What causes glazed brake linings?

Another benefit of the "door" spring around the drum is to help disapate heat. I wouldn't glue rubber to the drum, as that would hold in the heat. We always used large rubber bands on the drums when we turned them on the brake lathe. This was to stop squeels and vibrations.
 
Re: What causes glazed brake linings?

Brent, yes - this is that set of brakes: new cast iron drums, new shoes and linings, drums turned and shoes arced, Flathead Ted floaters front and back. Three of the four corners seem fine; I'm still chasing the squealing problem on the right front. :(

Bill, the lube would be a great solution if I didn't have other concerns.

I want to get rid of the over-heated drum situation and cure the squealing issue!
 
Re: What causes glazed brake linings?

Pilotdave said:
Brent, yes - this is that set of brakes: new cast iron drums, new shoes and linings, drums turned and shoes arced, Flathead Ted floaters front and back. Three of the four corners seem fine; I'm still chasing the squealing problem on the right front. :(

Bill, the lube would be a great solution if I didn't have other concerns.

I want to get rid of the over-heated drum situation and cure the squealing issue!
Click to expand...
Dave,
"MAYBE" you have something, not releasing properly, due to friction "somewhere"?? "Maybe"?? the lubing "might" help.
I don't know much about Ted's Floaters, but I remember something about leaving a return spring OFF?? That don't sound COPUSETIC to me?? But what do I know???:confused: I'll just stick to all stock, except for the little "floater" anchor thingy for the wedge.
Bill W.
 
Re: What causes glazed brake linings?

Bill, the longer spring is not used with Ted's floaters. You make an interesting point about a possible friction issue. Thanks.
 
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