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Sanding disc brake rotors -- terrible squeal?!
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P180 is pretty coarse, really. OK for rubbing down a house window frame, perhaps. For polishing metal, I would be looking at 1200 grade minimum (and even then not on a brake disc).coffeehound wrote: »The P180 is apparently the grade and that is pretty fine so isn't too coarse, which is what I was thinking could be the problem. I'll !!!!!! now
If someone is nice to you but rude to the waiter, they are not a nice person.0 -
Sanding the discs is a really bad idea, because you are introducing an abrasive medium into the metal of the discs at a microscopic level. For maximum braking effort, you need both the discs and pads to be perfectly flat and free of contaminants. You wouldn't sandpaper the discs on your car.
And once again I will point out that numerous cycling groups including Bike Radar, Pink Bike, Road.cc, MTB Tips, Global Mountain Bike Network etc all recommend it
As an aside, if you google "sanding disc brakes" there are plenty of people who recommend it for car discs too Sam Vimes' Boots Theory of Socioeconomic Unfairness:
People are rich because they spend less money. A poor man buys $10 boots that last a season or two before he's walking in wet shoes and has to buy another pair. A rich man buys $50 boots that are made better and give him 10 years of dry feet. The poor man has spent $100 over those 10 years and still has wet feet.
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I will bow to your greater experience and wider reading, but in 40+ years of fixing and maintaining cars, motorcycles and bicycles, I have never once heard of anyone doing it, until this thread.If someone is nice to you but rude to the waiter, they are not a nice person.0
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You wouldn't sandpaper the discs on your car.
I would if they were rusty.
I had some discs fitted a while ago to my car that had been sitting about for a long time. Lots of rust (superficial surface rust). They were cleaned up by a brass wire brush cup on an angle grinder. Lots and lots of scratches.
No noise at all though and scratches were all worn away within a day or 2 from using the brakes.All your base are belong to us.0 -
I will bow to your greater experience and wider reading, but in 40+ years of fixing and maintaining cars, motorcycles and bicycles, I have never once heard of anyone doing it, until this thread.
Hence why anecdotal evidence is of less standing
Sam Vimes' Boots Theory of Socioeconomic Unfairness:
People are rich because they spend less money. A poor man buys $10 boots that last a season or two before he's walking in wet shoes and has to buy another pair. A rich man buys $50 boots that are made better and give him 10 years of dry feet. The poor man has spent $100 over those 10 years and still has wet feet.
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Not at all sure about sanding discs, but 120 grit is far too abrasive, disc rotors on motors usually get machined (lathe or grinder) or scrapped.
Dics should have a very slight amount of axial run-out to keep the pads separated, too much and the disc is warped.
Coppaslip behind the pad quietens things, also make sure you have not mislaid any shims or pad clips from the caliper. These little parts make a big difference to reducing brake squeal.0
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