Diagnosing warped rotors
 

Hi

Under moderate to hard braking, I hear/feel a vibration from the front of the car. The vibration is a sort or low pitched rubbing/rumbling that happens once per wheel rotation. Nothing happens under normal braking - I only noticed it while exiting a highway.

I suspect warped rotors, but I didn't do any panic braking or anything. The car was stored outside for the last 6 weeks, with temperatures varying between 10F and 45F, and today's the first time it got driven.

How can I be sure it's the rotors? Is there any other driving test I can do?

If I remove a wheel, what will tell me if the rotors are warped?


Finally, if the rotors are warped, what are my options? Can RX-8 rotors be "turned" or do they have to be replaced?

How long can I drive on rotors that are warped? I'd like to replace them myself on the weekend if it's safe to wait that long.....


I know that's a lot of questions, thanks in advance for any help....

When you are braking, do you feel the steering wheel move left and right..... that would be a sign of the front rotors warped. You might also feel a pulsation in the pedal, but that is more of a sign that the rear rotors are warped.

When I took my oem rotors off and measured them, there was still some material left above the min specs. But the problem with warped rotors, you have to cut to the lowest point and that might be below spec. Most places will cut them below that at your request, but that will cause your pads and rotors to overheat and wear out faster.

the easiest way to check for a warped rotor but not as accurate....
take the rotor off and place it on flat surface, then take a sheet of paper and try to slide it between the rotor and the surface at any and all points around the rotor.... again this is the poor mans way of doing and not a substitute for having them measured

Google "Centric Premium brake rotor RX-8" and find the cheapest price for a new pair of front rotors. It's probably cheaper than having them turned, as long as you are willing to install the new rotors yourself.

Rotors are made to be thrown away to save on weight of the vehicle.

There is not enough stock on them to turn it.

and we all know that rotors don't really warp, right?

and to be a little more helpful, try rockauto for new rotors. i bought mine from there and the price was awesome and the shipping was fast. i got cross-drilled and slotted for the fronts (yes, for looks) and slotted for the rear. as george said above, i got centric rotors.

Actually, most people don't. Even though 99% of the time it's just excess pad material throwing the rotor out of balance, people assume it's easier to warp a solid piece of cast iron.

Ah excuse me - but did anyone READ what the OP said? "Outside for 6 weeks" "1st time driven."?

That just shouts rust depoosit on the rotors, no warped rotors or pad desposits or anything but the fact that after leaving bare iron out to the elements - it's (suprise) going to rust.

So advice would be - go do some high speed stops on the interstate, vibration should go away or lessen after braking...and over a short time of continued driving...go away. If you're really anal about it, take each wheel off and use some sandpaper/steel wool or a drill with a sander disk and get rid of the deposit....it should be relatively easy to see or at least feel.

actually no. if the rotor is partially overheated, the material will become hardened and the rotor will have uneven wear. think of flywheel.
http://www.youtube.com/watch?v=KeqzZniVmrM

This. I drove 80 miles (mostly highway), and it rained the whole way. Looks like whatever was causing the vibration washed away, my braking (even moderate to heavy) is vibration-free. Thanks for the help, all! I appreciate the tips - I'll look at the rotors next time I rotate the tires....