Bent wheel, broken tire belt, rust or scale stuck between the rotor and hub, tire out-of-balance.
Where do you feel the vibration now; seat, steering wheel, or whole car?
October, 9, 2012 AT 12:17 AM
Sometimes the steering wheel and sometimes it feels like my seat/ tires. But only on highway and downhill
October, 9, 2012 AT 12:19 AM
I haven't changed my back brakes in quite awhile which are drums. Could this be apart of the problem
October, 9, 2012 AT 12:28 AM
Start by running it in gear with the front wheels jacked up and the car supported on jack stands. Watch the spinning tire from the front to see if there's any sideways movement in the tread or a noticeable hump on one side of the tread. A little movement is normal but if you see more than about 1/8", that's cause to look closer.
Next look at the edge of the wheel where the weights go. 1/8" there is way too much. Typically only one wheel will be spinning. You have to carefully stop it to make the other one start spinning. I do that by wedging a 2x4 under the spinning tire but be careful because if it's laying close to the ground the tire can shoot it out if it's spinning fast enough.
You can also identify a tire or wheel problem by switching them front-to-rear, then see if the characteristics of the vibration are the same.
If you see one wheel wobble, pull that one off, then run it in gear again and watch the brake caliper. If it's moving side-to-side, even a little, your new rotor is warped or there is something stuck between it and the hub. Both of those are common. A cut on the brake lathe will true up the rotor. Usually once they're machined they typically don't warp again.
A hard-to-find cause of a shimmy in the steering wheel is a worn inner cv joint housing. I won't describe that now because it's pretty involved to check and it almost always shows up only during acceleration
October, 9, 2012 AT 12:32 AM
Drum brakes don't cause a vibration while driving unless a big chunk has rusted off creating an imbalance. If a drum is egg-shaped you will feel a tug and release sensation when holding steady pressure on the brake pedal. The brake pedal may or may not rise and fall slightly depending on how the drum is shaped. You won't feel that in the steering wheel.
October, 9, 2012 AT 3:37 AM
When I changed my rotors I didn't change my pads because they still have a lot left think its possible my pads are no good. If so what do you think about sanding them down a little
October, 9, 2012 AT 3:38 AM
Like they wore down unevenly because of warped rotors
October, 9, 2012 AT 5:10 AM
Nope, pads won't do that. Uneven wear is normal except GM has an unusual master cylinder design that can plug the brake fluid flow to one front wheel and the opposite rear one. Due to changes in suspension geometry you may not notice a loss of half of the braking system. Often the only complaint is the pads are worn down on one side and they look like new on the other side.