Brake discs

For some reason I can't keep my brakes from squealing. Recently I had my brake discs machined to have them plane again and the pads renewed. The squealing was gone - for about 1000 miles, when it started again.
We looked at the discs and they already had some new grooves in them, which according to my mechanic are causing the squeal. He thinks the steel of the discs might be brittle because of age...
I don't know if this is really true. In any case, I would like to know if anyone has any experience in installing newer discs, preferably cross-drilled. Are they exchangeable with 400's, 412's or other models? Or is there maybe a company that provides better discs?

Thanks,

Howard

 

Hello Aidan,

this seems to be a whole science for itself. My mechanic, as I mentioned, claims that the squealing comes from the grooves in the discs and subsequently the pads as well. Where those grooves, however, come from, he couldn't really say. It might as well be the calipers. What I don't understand, however is, how do those grooves come to existence when you start off with a plane disc and a smooth brake pad? The other thing is that when I got my car a little over a year ago, I had the entire suspension, steering and brakes overhauled. I asked my mechanic to exchange anything that seemed to have the slightest problem or wear. In the end he found the calipers to be in perfect working order. Therefore, if I was to rebuild the calipers, what should I be looking for..?

 

Hello Boyd,

I've sent you a PM in regards to your offer. Thanks.
From your S/N I take that you own a 365 GT4 2+2 as well. It seems there aren't two many 365 GT4 owners among the f-chatters. One thing that would interest me is, is, or was your dash originally also covered with "mousehair" or is it vinyl or leather? The reason is, that I claimed in another thread that most cars were actually covered with mousehair, since all the 365 GT4's I have seen so far were.
Here's a picture of my little baby, S/N 17251
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Hello Ken,

what you said about cross-drilled rotors actually makes perfect sense. And of course the high temperature grease was our very first option to try. It didn't help much. The only thing that really helped was planing or machining the rotors - for about 1000 miles, as I mentioned. Now the squealing is coming back slowly but by far not as bad as before. Before, unless you really stepped on the brakes really hard or touched them ever so slightly, they squealed like a two-mile-long freight train coming to a halt. Driving in town, two entire blocks would turn around and stare at you, some people even covering their ears. Then they gave you this regretful glance that said: "looks really nice but what a piece of crap it must be..."
In any case, this of course also has something to do with the fact that these brakes were originally designed to use asbestos pads. My first mechanic - who later turned out to be a total failure - even went as far as to say that I would never get rid of that squealing unless I used asbestos pads. This, of course is total BS. The squealing comes from the grooves in the rotors and the subsequent grooves in the pads. If you put on new pads they won't squeal until the grooves from the discs are imprinted in them. Therefore a plane rotor will never squeal. I'm just not a 100% sure what actually causes the grooves in the rotor. Most likely, however, it has to do with the quality of the steel of the disc that could be affected by metal fatigue or, as you said, by overheating.
So for now I'm concentrating on finding new discs. It'll be interesting to see what Boyd has to offer. I'll keep you guys posted.
So far, thank you very much for your help.

Howard