Hyper_545i

Hello All,

I replaced all four rotors, front and rear pads as well as sensors about a year ago. I've put maybe 10k miles on them and just discovered the front rotors are warped. I am getting the rotors replaced, but the question is, can I re-use the existing pads? I've searched the internet and found a 50/50 split on the decision. I have even heard the argument of using old pads to bed the brakes and then replace with new pads once bedding is complete. Any help would be greatly appreciated.

Also, if new pads are not needed, do you have to go through the bedding process again?

Hyper_545i

Anyone?

M3Mongo

I personally wouldn't reuse the old pads. They were seated to the old rotors that you said were warpped. If you can afford getting new pads I would. At the very least get knew front pads.

abe76247

I have been in this situation in my shop several times. Get 100 grit sand paper and sand off the face of the pads on a flat surface. Install them and bed them in like they were new.
Make sure your caliper mount hardware is free and lubricated well. The retainer bolts should be lubricated too (not the mount brake to spindle, the caliper to mount bracket). The absolute best and technically correct way is to check runout of rotor mounted on hub with a dial indicator and move rotor to the lowest lateral runout position of the 5 positions available. If the runout is excessive then the hub needs to be checked. I would have to dig up a spec but I bet the rotor runout is not supposed to exceed .002 inch.

If you had a warped rotor BMW would only replace rotors under warranty if the pads were more than 50% worn. On domestic makes where maching untrue rotors is the way brake vibration is addressed you re-use the old pads. I have done it loads of times and never had one issue.

When you bed in pads and rotors you are finishing the curing process of adhesives used in manufacture and are depositing pad material onto rotor face. The brakes only reach full effectiveness when the pores of the metal of rotor are filled with pad material. Used pads will do this just as well as new pads.

twh

If you have fairly new rotors and one is warped, maybe you have a stuck caliper. There is a pin it slides on and if that pin doesn't slide, you get a stuck rotor and heat build up. You should check that.

As far are pad replacement. Technically speaking, you get the best performance (i.e. braking) when you replace the pads. The old pads have worn to fit the old rotors. But, if 100% day-one isn't important to you and the pads don't have big grooves, in them, you'll be ok. The pads will eventually wear to the new rotors. Until that time, you just don't have 100% braking.

e6t.lab.rat

Check to see if your pads are worn down evenly. If not, and one pad is thicker than the other then you have a caliper that is sticking, which can cause your rotors to warp. Do this simple visual to eliminate a sticking caliper. Good luck

texasmr2

I agree that this would be the simplest way to check for a sticking caliper. Also I would think/believe that if new rotors are warped after on 10K miles the caliper is the culprit.

As mentioned Good Luck and I look forward to the diagnosis.

tonyb635

Why even chance it ? If you're throwing new rotors up on her I would just replace the pads too. Otherwise it might be a wait a see if they warp from the old pads. If you can't afford new pads then that's another story. But at a minimum I would replace the front completely.

Hyper_545i

Thank you all for the responses! I have new rotors on order and they should be in today. I will definitely check the pad thickness and compare and look into to se if one of th calipers are sticking. Although I believe there would be other symptoms of a sticky caliper, car pulling to one side more brake dust on one wheel etc.

I have been reading that the brake vibration could be caused by uneven pad distribution to the rotor. I am going to try re-bedding the pads to see if this cures the steering vibration. I highly doubt the rotor is warped at this point. Even if the brakes/rotors were bedded properly an uneven friction deposit on the rotors could cause the vibration. I do a lot of highway driving, but there have been numerous occasion when I would have to brake heavily on the highway and come to a stop. While the brakes are hot, holding the pedal down while stopped will cause an imprint of the transfer from the brake pad to the rotor. I always thought bedding was a one time process, however I read that is not necessarily true. I am going to try bedding the pads again to see if that cures the issue. If not, I will verify the caliper is not sticking install the new rotors, scuff the exisiting pads (after inspection to ensure no grooves) and re-bed. I have actually heard bedding in old pads with new rotors is best, assuming the pads ahve plenty of life and have no irregularities. Depending on how they look, I may just buy new pads altogehter. I will update with my findings.