Brake Rotor Question For 2004 Silverado 4x4 Ext. Cab

lowcountry · February 2, 2009

I need to replace the pads on the rear of my 2004 silverado 4x4 ext. cab with 85,000 miles. I am hoping to have enough rotor to have them turned at a machine shop. My question is about the run out shims and when do you use them. How do I determine if a shim is needed and what size to use? Does having the rotors turned or replaced effect the shems needed? I figured since they sale the shims, it isn't as easy is just throughing no pads and rotors on and calling it a day.

Thanks

PS I tried searching through the forums and couldn't find any information.

Supertech64 · February 3, 2009

Shims are generaly only used it you have a shake and your rotors are already true.

You would need a dial indicator to check runout to determine what shim you would need(installed behind the rotor with the thickest part 180 degrees opposite of maximum rotor runout)...and that is generaly done after you machine the rotor.

Edit: Just a though, you could always find someone with an on-car lathe and skip the whole need for shims.

lowcountry · February 3, 2009

Shims are generaly only used it you have a shake and your rotors are already true.

You would need a dial indicator to check runout to determine what shim you would need(installed behind the rotor with the thickest part 180 degrees opposite of maximum rotor runout)...and that is generaly done after you machine the rotor.

Edit: Just a though, you could always find someone with an on-car lathe and skip the whole need for shims.

Thanks so much for the info. I do have a little bit of feedback in the pedal when I am on the brakes. I will measure for any runout after I get them turned, if they even need to be. I looked at them last night and ran my fingernail across and I don't feel any groves and there are no hot spots. I am wondering if they even need to be turned now. Is there anything I should be aware of with the parking brake when I pull the rotors off?

Thanks,

Supertech64 · February 3, 2009

If you have pullsation when brakeing I would turn them, it will most likely clear that up and give the new pads a nice surface to seat to. You can never really tell by sight and touch if they are out of round anyway.

As far as the park brakes go, check the edges of the friction material for wear. They had a problem at one time with just the edges wearing out not the centers and the parking brake not holding well.

They normaly stay in position pretty well, there may be a little bit of a lip on the inside of the rotor and you may have to persuade it off, but generaly they come off pretty easy and nothing odd happens.