Hey all,

Taking my OUtie in to have that weird brake noise that I have been experiencing.

However I have noticed that certain areas of the rusty lip of the rotor (the outer edge) is shiny and some parts aren't...meaning that the pad is clipping certain parts of the lip.

Is it safe to grind that lip off? The rotors look good other than that lip. No vibration, no lack of stopping power, just a very annoying noise. The truck has 108,000KM on it - original rotors and pads. I am thinking of getting Wagner thermoquiet soon and just need to know if I need new rotors as well.

thanks!
dave

 

I'll cautiously say you can...however I think if you did it yourself with a grinder, you may run the risk of not being even throwing it out of balance. then again, if you do, then you just need to get new rotors put on. worth a shot.

 

Grinder may alter the rotor balance if you take it too deep and could give you some harsh edges. Just use a wire brush and a metal scrapper to get the rust flakes off by hand.

This is all a stop gap until you replace the rotors. They'll just rust up again.

 

i have never ground that down. but i have pulled rotors, blasted and powder coated them... then had them re cut...

 

Is the wearing part of the pad so thin that some part of the metal backing that is adjacent to the wearing part starting to touch the raised, rusty ridge on the very outer edge of the rotor? If yes, and the rest of the rotor that the wearing part of the pad normally touches is not gooved, you're lucky. If I were in this situation, I'd replace only the pads and, after installation, visually confirm that the wearing part of the pad is at the very inside edge of the ridge (right where the edge of the old pads' wearing surface used to be). If it is, go for a short test drive to hear if the sound has disappeared. If it has, I'd just keep driving. If the noise is still there, replace the rotors.

 

find your local friendly guy with a lathe, take him beer, and have them skimmed.

 

Hey,

so I took it to a local guy (independent) and he thinks the same thing I thought - that the rusty lip of the rotor is hitting the pad and that if new pads go on, the noise will still be there.

His solution - HE WANTS TO HIT THE ROTORS WITH A HAMMER all along the outer edge knocking the rust off, and then grind the lip away.

He said the rotors are looking really good other than the build up of rust around the edge. The surface of each is really smooth.

Before I knew it, he started hitting the front of right on the edge (imagine rolling the rotor along the ground....the hammer was hitting the part that is making contact with the ground). A boatload of rust fell off. It was only a few strikes, but he wanted to demonstrate it.

He said he does this all the time and not to worry - the hammering won't damage anything as long as the surface of the rotor where the pads make contact don't get hit.

Can anyone verify this? I questioned him ALOT on this...he said it WILL NOT DAMAGE the rotors.

Thoughts?
Thanks!

 

Uuuuh, you're on your own with that one. I would have just had them turned on a lathe.

 

a hammer is one of an engineers most useful tools.
Unlikely to do damage.

A grinder will put heat into your rotors, in a fashion they werent designed for.

 

The one and only reason the cast-iron rotors' surface looks really good is that the pad wears off any film of rust that does indeed form when the vehicle is at rest.

But there is almost always a very small portion of the outer edge of the rotor that the wearing part of the pad does not touch, so the rust just keeps building up and forms that typical ring of rust.

Even though the ring is always there to at least some extent, there usually is no noise when braking. The rust can and will never encroach under the pad because, again, the edge of the pad just brushes it away, forming a nice razor-sharp border between the shiny rotor and the rusty ring.

But when the wearing part of the pad wears down to very thin, now the metal "backing" of the pad, which can be just a bit larger than the wearing part of the pad it supports, can begin to rub on the rust, causing a light rubbing/grinding, metal-on-metal noise. When the pad wears out completely, the entire metal backing begins to touch the rotor and then the noise gets much louder and starts cutting grooves in the rotor.

If you replace your present OEM pads with Mitsubishi pads, again, there is a very good chance that the grinding sound will disappear completely, because the shape of the wearing-part of the new pads will be identical to that of the old.

If you replace with aftermarket pads, they may be a slightly different shape than the OEM and the wearing part of the pad may overlap the rusty ring just a bit. In that case you may hear some slight grinding. At first the rusty ring will very quickly cut a corresponding groove in the pad that will be almost as deep as the height of the rust above the rotor. As the groove is cut, the rest of the pad will very soon make contact with the smooth part of the rotor and the groove will not be cut deeper. From that point on, because rusted cast iron is not anywhere near as resistant to abrasion as un-rusted cast iron is, as the pad wears down naturally on the smooth rotor, the portion of the pad over the rusty ring will wear down the rusty ring the moment the rest of the pad allows it.

So, if the rusty ring stands say 1/16" above the shiny part of the rotor when the old pads are removed, after the new pads are installed, the first application of the brake will force the pad to wear down the rust a considerable amount as the rust cuts the groove in the pad. Because of the "work" the rusty ring has done on the pad, now the "top" of the rusty ring sits well under the 1/16" above the shiny part of the rotor that it used to be. Once the wearing part of the pad over the shiny part of the rotor decreases in overall thickness that amount, the rusted portion of the ring will have been worn down by the pad to shiny metal. That now-shiny ring will still be slightly higher than the rest of the rotor, but only an insignificant amount and, because it will now be as shiny as the rest of the rotor's surface, there will be no brake noise -- noise that will likely have stopped very shortly after the new pads were installed.