constructr

Hello,
I have a 2012 RX 350 and the brakes are pulsating AGAIN after only 8000 miles. In 6 months I've been through 2 sets, both front and back..
Anyone know of a known brake issue like this??

Thanks,

ukrkoz

Yes. You are not bedding them in.
Also, your caliper sliding pins are likely stuck not allowing caliper to slide on them as it should. What leads to overheating and faster brake pad materail build up on rotors. Rotors do not warp.

Myth # 1 – BRAKE JUDDER AND VIBRATION IS CAUSED BY DISCS THAT HAVE BEEN WARPED FROM EXESSIVE HEAT.

The term "warped brake disc" has been in common use in motor racing for decades. When a driver reports a vibration under hard braking, inexperienced crews, after checking for (and not finding) cracks often attribute the vibration to "warped discs". They then measure the disc thickness in various places, find significant variation and the diagnosis is cast in stone.When disc brakes for high performance cars arrived on the scene we began to hear of "warped brake discs" on road going cars, with the same analyses and diagnoses. Typically, the discs are resurfaced to cure the problem and, equally typically, after a relatively short time the roughness or vibration comes back. Brake roughness has caused a significant number of cars to be bought back by their manufacturers under the "lemon laws". This has been going on for decades now - and, like most things that we have cast in stone, the diagnoses are wrong.With one qualifier, presuming that the hub and wheel flange are flat and in good condition and that the wheel bolts or hat mounting hardware is in good condition, installed correctly and tightened uniformly and in the correct order to the recommended torque specification, in more than 40 years of professional racing, including the Shelby/Ford GT 40s – one of the most intense brake development program in history - I have never seen a warped brake disc. I have seen lots of cracked discs, (FIGURE 1) discs that had turned into shallow cones at operating temperature because they were mounted rigidly to their attachment bells or top hats, (FIGURE 2) a few where the friction surface had collapsed in the area between straight radial interior vanes, (FIGURE 3) and an untold number of discs with pad material unevenly deposited on the friction surfaces - sometimes visible and more often not. (FIGURE 4)In fact every case of "warped brake disc" that I have investigated, whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures.

PREVENTION

There is only one way to prevent this sort of thing - following proper break in procedures for both pad and disc and use the correct pad for your driving style and conditions. All high performance after market discs and pads should come with both installation and break in instructions. The procedures are very similar between manufacturers. With respect to the pads, the bonding resins must be burned off relatively slowly to avoid both fade and uneven deposits. The procedure is several stops of increasing severity with a brief cooling period between them. After the last stop, the system should be allowed to cool to ambient temperature. Typically, a series of ten increasingly hard stops from 60mph to 5 mph with normal acceleration in between should get the job done for a high performance street pad. During pad or disc break-in, do not come to a complete stop, so plan where and when you do this procedure with care and concern for yourself and the safety of others. If you come to a complete stop before the break-in process is completed there is the chance for non-uniform pad material transfer or pad imprinting to take place and the results will be what the whole process is trying to avoid. Game over.

constructr

Thank you ukrkoz.

So, my rotors are about 3 months old. All 4. Should I just get the rotors re-surfaced and new pads installed and have them bedded in properly ??

Clutchless

Usually the bedding is best done by the car owner right after he gets the car from the shop. I do my own brakes but doubt that a shop tech is going to drive around and bed your brake pads for you. They probably just do the work then park the car.

Look at these links for some more detailed instructions https://www.autoanything.com/brakes/how-to-bed-in-brake-pads

https://www.powerstop.com/brake-pad-break-in-procedure/

Note they are very similar. It could be your rotors could just be cleaned up with a hone rather than resurfaced. I bet there are not that many deposits as it has only been a short time.

tus

In almost all cases I've seen, warped rotors have been caused by over torquing of the lug nuts, or, not having even torque on each one of them.

Assuming that the OP has taken the thing to the same guy twice now, my guess is they are just grabbing the impact and blasting the lug nuts on with whatever the thing is set at.

Clutchless

Good possiblity since the torque of the wheels is only 76 foot pounds.

jrfiero

tman9999

sbrown329

WOW, what an awesome thread! I never knew...