leoferus

There's a lot of information out there about brakes. Here's what matters to us from Toyota/Lexus:

That's step 4C of the front brake inspection procedure. So, let's forget the word warp. Let's call it runout. That's what Toyota calls it. Their engineers have been doing this for a while. I'm sure if they think it's real... it's real. But I am more likely to believe that composite rotors do not develop runout... They just get traded in because most people can't afford to replace them ;-)

In truth, nobody can diagnose your car via the forums. A brake pulsation is a symptom of a condition. You'll need to perform a thorough inspection in order to determine how and why this symptom presented itself. If I were your mechanic I would not start doing anything to your car until I can explain why you are experiencing the condition you're concerned with.

If your brake pulsation manifests itself in a vibration of the steering wheel at moderate speeds, I'd focus on the front brakes. If the vibration is felt more in the seat of the pants, I'd focus on the rear brakes. If the brake pedal seems to be slightly spongy, I'd scrutinize the calipers and hardware... etc, etc, etc.

P.S. I've had more success eliminating runout using an on-car lathe rather than a bench lathe. Toyota recommends the use of an on-car lathe for their products as these machines calibrate to the vehicle and reduce runout accordingly, well, ProCut does.

And not all technicians are the same. Some are much better than others at resurfacing brakes.

andper10

Good point, technically rather than saying my rear rotor was warped, I should have said that it developed uneven brake pad transfer caused by the stuck caliper slide pin which caused cementite to develop on the rotor surface which caused excessive lateral runout as measured on the rotor and resulted in the rear end shaking under heavy braking. The end result was the same though, it required replacement of the rear rotor, pads, and caliper. I replaced them in pairs since the slide pin on the other side was starting to stick also.

Thanks for informing me; I have revised my post. I also discovered there are inexpensive available.

isfvss

So its all in a word run out or warped, if you have ever watched brake drums or discs being machined you would see a lot of metal coming off the warped - run out area . I have worked on buses trucks and plenty of old and new cars, in this day and age of throw away society sometimes it makes no $ sense to machine a warped, run out disc which is the major cause of brake shudder.

leoferus

Toyota engineers call it warpage at school. We're not seeing materials being deposited on the rotors as being the cause of runout. We're seeing that the rotor surface is undulating. When I resurface rotors with runout I'm seeing a ferrous material coming off the rotor. This might not apply to all manufacturers but Toyota brakes are designed so that the pad deforms rather than the rotor. When the rotor deforms it's due to a number of reasons. In my 10 years with Toyota they have been: 1) Aftermarket pads. The materials used in cheap aftermarket pads cause overheating that can be seen as hot spots on the rotor. Akebono is one of the few aftermarket pads I've seen work well on Toyotas visiting the dealership. 2) Stuck pins. 3) Seized caliper 4) Overheating. Technically, all of the above are the result of various forms of overheating. This one is particular to places that use salt in the winter to combat snow and ice. The vents develop significant rust and this prevents the rotors from being able to shed heat fast enough.... somehow this results in material deposits that result in an uneven rotor surface... or, maybe, they result in warpage... you know, the metallurgical term for a metal that deforms due to extreme temperature change, etc. Anyways, the above not a definitive list. Oh, a major one is that the rotors are close to or below minimum spec. The available amount of material isn't enough to dissipate heat fast enough, therefore, warpage.