[LawrenceS]

Warped Brake Rotors—The Facts

While that may be true in some instances, I have seen plenty of rotors that are actually warped as a professional automotive tech. In the Honda world the 09-15 pilots and 12-17 odysseys constantly have rotors warping. The exact reason I am unsure, but I speculate it had something to do with the front and rear brakes being undersized for the vehicles. Front's being undersized allowing for a greater build up of heat in the rotors and rears being undersized causing the fronts to work harder. For the odysseys Honda even updated the rotor design for improved cooling.

 

[LawrenceS]

Ive never seen brake pad material (fuse) to rotors or drums. Thats on motorcycles to tractor trailers and everything in between.

It does happen to an extent, I believe it's why we end up seeing the glossy finish on rotors and while it may account for some thickness variation, I've had enough rotors on a lathe to also see that metal gets removed not just adhered friction material to get a rotor flat again.

Mostly when I see pad material fused to a rotor it's because a vehicle hasn't been driven and some sort of reaction happens between the friction material and the rotor leaving a noticeable build up(real common on 07-16 Honda CR-V rear rotors). As a professional tech we would just resurface them but realistically you could grind the build up off with an abrasive disc on an angle grinder. Not sure how long that fix would work/last though.

The other thing I have noticed when they do leave a build up from sitting, even when you resurface them you can get the rotor flat but still see the outline of the brake pad where the build up was.

 

[LawrenceS]

Glossy finish is glazing. Again, from misuse or excessive heat (faulty components).

If you guys can come up with more than one dumb website saying brake pad material transfers/bonds to rotors/drums I may believe you. But for now and from my long term experience, its b.s.

Every rotor I've ever seen glazes, google what glazing is, transfer of pad material to the rotor.

GLAZED AND CONFUSED

Poor brake performance got you baffled? It could be glazed brake pads and rotors. Top braking performance relies on friction—in other words, the brake pad’s ability to grab onto the metal brake rotor. When that ability is compromised, brake performance can go by the wayside faster than that turn...

sunstar-braking.com

.

Also I'm not a hobbyist, I fix cars at a high volume dealership for a living, 15 years in the industry, ASE Master certified with L1 and Honda Master certified.

 

[LawrenceS]

Glossy finish is glazing. Again, from misuse or excessive heat (faulty components).

If you guys can come up with more than one dumb website saying brake pad material transfers/bonds to rotors/drums I may believe you. But for now and from my long term experience, its b.s.

Sorry to bump an old thread but I had a perfect example of pad material transferring/bonding to the rotor, not from driving but from sitting for an extended period.

Before

Cleaning the deposited material off with a Scotch Brite roloc disc on a mini angle air grinder.

After resurfacing the rotor - you can still see somehow the pad material has effected the rotor metal - not sure exactly what happens.

 

[LawrenceS]

Those are some interesting pictures, LawrenceS. It does support the transfer of pad material to the rotors.

I'm still trying to figure out how warped rotors supposedly cause the brake pedal to pulse. Warped rotors would still be the same thickness everywhere. The entire caliper would potentially move, sliding on the pins, but the piston wouldn't move.

That type of pad material bonding to the rotor typically causes more of an audible thump versus a feeling in the pedal.

Warping may not be the proper term used in metallurgy for what happens to rotors but it has become the common place term to use. Technically pulsation comes from runout or parallelism. I understand what you are saying that if the metal warped one would expect the thickness/parallelism to be the same all around even and it would just have positive runout on one side and negative on the other side because the metal moved as one piece in 1 direction. Brake pulsation typically comes from the front rotors, which are all pretty much vented(the vanes in the middle between the two surfaces) so maybe it's something with the vanes warping and pulling one or both sides of the rotor inward because typically when cutting a rotor the warped area appears as a low spot not a high spot.

And even with warping like your envisioning, what ends up happening is it's felt more in the steering wheel because as the caliper is following the rotor it ends up pushing against the knuckle through the caliper causing the steering to move.