Acceptable rotor runout?

[gearheads78]

I have been chasing what I thought was a rotor problem the last couple of days. When I slipped the rotor oven my drum hub I could see the wobble. I put a dial indicator on it and I was at .035 runout, I took the rotor to work and put on a brake lathe and it was OK.

Messing with it again this morning I found that there was a high spot on the face of the hub. I filed that down and now I am at .005 runout.
That should be OK shouldn't it?

[chicane67]

0.001 to 0.005" is tolerable... with 0.005" being max.

[Apogee]

High spot? Are your hubs bent or damaged in any way?

Assuming the hubs are not garbage, I'd chuck up the hub in a lathe, dial it in off of the bearing bore and then reface the flange. You should be able to reduce your runnout by half if not more. Every little bit counts. Just for reference, most of our hubs install with .0005" to .0010" total indicated runnout.

Tobin
KORE3

[gearheads78]

It was not damaged or bent just had a about 3/4" spot that was .020 higher than the rest of the face. I filed it down and managed to get the total runout at the edge of the rotor to .004

Tobin, I talked with you last week about my rear LS1 brakes. I must of written something down wrong. I thought that you said LS1 rear is 2.770" from face of the axle housing flange to the face of the axle where the rotor sits. My Olds rear is 2.750" for the same measurement so .020 difference should be no big deal. I put it together this weekend and it seems like the backplate is way off and needs to come out apox 1/4"-5/16" looking by my eye.
Can you confirm the measurment of the LS1 rear?
Thanks

[Apogee]

Late-model GM 10/12-bolt c-clip axle has a 2.77" brake offset dimension, early is 2.81" for the mid-size cars. Am I correct to assume that you are using all LS1 F-body rear brake compenents? Did you happen to take any pics while you were putting things together?

Tobin
KORE3

[gearheads78]

Late-model GM 10/12-bolt c-clip axle has a 2.77" brake offset dimension, early is 2.81" for the mid-size cars. Am I correct to assume that you are using all LS1 F-body rear brake compenents? Did you happen to take any pics while you were putting things together?

Tobin
KORE3

Yes all LS1 rear brakes going on a 72 Cutlass 8.5 rear with bolt in axles

I think I have it figured out. I have been trying to find someone with an LS1 rear end to measure off of all weekend but no luck. I am assuming I want the rotor to be perfectly centered with the basket. Right? If so if I add .125 between the axle and the backplate I will be dead on. I tried with washers tonight to simulate this 3/16" plate
http://www.brphotrods.com/Rear%20Brake%20kit.html using 3 .070 washers to get close. It was too far out. I had .280 space on the outside and .110 on the inside so .195 each side would center it. Thats where I get the .125 spacer will work