extanker

^^^^ agree......or see what happens when some one puts a wheel back on improperly eg impact gun /uneven torque/non star pattern .......you will be a warp believer or untrue disc ....even a piece of rust between the rotor and flange will make a steering wheel move/brake pedal pulse or rear discs will shake you in your azz on the seat. the op could take it to a brake shop and have them check for true if is not out by much have them true it if allowed,might only charge 20 bucks to true

ScootCherHienie

For the record, I never said warped rotors are the only cause of vibrations under braking. Certainly a rust spot on the rotors from being parked a few days in rain/humid climate can cause vibrations in the brakes as can any sort of unevenness in the coefficient of friction over the surface of the rotor. But warping also happens... when a BMW I had always had vibrations under braking after 3 hour or longer trips on freeways at 70mph, the dealer finally got tired of replacing warped rotors and finally replaced the 2 front calipers (which I had been telling them was the likely problem for 8 months) and no more warped rotors... the original calipers were not releasing enough pressure on the brake pads causing them to drag on the rotors too much causing the rotors to get quite hot after a few hours at 70mph. You can also warp rotors by getting them really hot, stop, then hold your foot on the brake pedal so the area with the brake pads touching cools at a different rate than the rest of the rotor. Vibrations that go away after days or weeks of driving were clearly NOT warped rotors--and that has happened to me also.

deilenberger

Rotors can BE warped by improper torquing of the wheels.. BTDT and was I pissed..

mtnrat

Update. Went out this morning and sanded the new rotor to see if there were pad deposits on it. Now only takes 20 min from ground to back on ground. lol Took it for a spin. 90% of the shudder is gone. Tells me the thing is not warped. Went through the re-bedding procedure and put it away. Will check it out this afternoon.

TomF

There you go.

Glad to hear that you are on the way to having it sorted out. Read the article. It is worth the time.

Cheers,
TomF

extanker

did you have to remove the wheel to sand the rotor ?

deilenberger

I'm not mtnrat - but I can't imagine any scenario where one could sand a rotor with the wheel still on. If you can - please tell us how.

mtnrat - there are ball type brake hones available for not too much money meant for exactly this purpose. I seem to recall the one I bought being about $40. It fits in an electric drill. If it's just pad-poop the brake hone should clean it up. I had an odd issue with some stainless steel rotors on BMW motorcycles, where pads would rust to the rotor if it was put away wet - and the metal actually changed under the pad due to electrolysis. The brake hone couldn't cure that one.

mtnrat

I removed the rotor and did it on my bench with a flap wheel on a drill.

mtnrat

I think I will take them to my buddies shop and have him shave off a super thin amount. If I did that would it be a good idea to get new pads?

Matt O.

Rotors do not warp. It is uneven initial pad wear and surface adhesive shipped on pads and rotors.

extanker

my asking about removing the rotors was meant to see if a piece of rust/dirt was between the rotor and flange and that fixed the whatever . as far as not removing it......i have read things on this po forum from [haha] engineers .....and they should not be allowed to own tools

prosled8

The rough surface after turning the rotors down should be enough to bed in the slightly used pads just fine. You might take your flapper wheel to the pad surface or maybe just a little hand sanding to get a fresh surface there too. The pads should be fine though.

mtnrat

That was my first inclination. Took them off and made sure all mating surfaces were clean.

deilenberger

If there is any glaze on the pads - some 400 grit aluminum-oxide paper on a piece of plate glass - rub in a figure 8 motion - and don't sand one edge more than the other - should fix them right up. Gives a fresh surface to bed in on the fresh rotor surface.

mtnrat

Will do.