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Last week there was a discussion about shimming rotors. It was over debated without a doubt. I am not looking to start another debate, in fact I am not going to respond most likely.
However, there are some who don't get it so here is an original GM axle. I checked it for press fit, cleaned and polished it, again keeping track of the dimensions.
I chucked both axles and checked the flange for runout. Keep in mind, this is in a 3-jaw chuck, not a collet or dialed in a 4 jaw. 002" for both. I fully expect the new rotors to have runout over what I accept so if needed I will shim them and lock them in. It will not make a difference if I cut these axle flanges, the final assembly will determine dial- in requirement.
That is where I stopped reading in that thread....when it was suggested some MIL spec machining procedures be performed on a f%&king street car......you could machine all of that to +/- .0001 and by the time you bolted it all together it would move a thou......
Gary since I cannot find the old NAPA/Raybestos rotor shims, what do you recommend to use for shims under the rotor?
I would first confirm what your runout is. Then I would check the mating surfaces closely. I had to remove a small burr that was 006" high. Countersink the inside hat holes and use a die grinder around the holes in the rotor hat and flange. Then if you still have runout I use SS shims stock to make my own. Not fancy looking but work. Those shims Jebby shows should work too. I have seen guys use soda can, various shim metals and they all worked, and no one's wheel came off all these years later.
I finished up these arms today so I wanted to post the runout results.
LH arm 004" no shim, i want better than 004" so I set it to 002" shimmed. I have no concern or fear of the wheel coming off using a 004 SS piece of shim stock. The rotor is not loose or warped.
Those are not rivets, they are socket flat heads. I use them because I like to keep the runout locked in.
when doing rotors you can :
1- do nothing and use the lug nuts, runout may vary with wheel changes
2- Rivet and turn them as GM did. This works and works probably the best as there won't be any runout. But if for some reason you need to get into the parking brakes you have to drill out the rivets again.
3 - Bolt them on, hold the runout locked in and allows access if needed, much easier. That's how I do them 99% of the time. the 1% I don't usually is with some of the 1/2-20 studs I use building 31's.
Rotor Runout
