Trailing Arm HELP!

[Brandon K.]

I just installed my trailing arm assemblies on my 67, and I notice that when I spin the brake rotor, there is a lot of variation in the distance between the inner part of the rotor surface and the caliper mount. I assume that what I am seeing is what everyone refers to as "runout", and it appears to be well over 1/16 of an inch. Isnt that WAAY over spec?

The assemblies were just rebuilt by Van Steel, and given their special "alignment" treatment. Am I imagining that there is a problem, or do I have real reason to be concerned?

Thanks for your help w this one, guys.

Brandon Korman

[Gary Schisler]

Re: Trailing Arm HELP!

Normally, when the runout exceeds .008-010" (8/1000ths) you will probably have some braking problems. Given Van Steels reputation, I would suggest that you check other areas to insure that you do have a problem. Do you have access to a dial indicator? Of course, even with a quality shop like Van Steel, it is possible that a bad apple slipped into the system. I had a bad rotor and ordered a replacement. After I installed it I noticed that I had worse problems. I took the new rotor down to my local machine shop and they measured .012" runout. After careful machining, I put it back on and the problem was solved.

Gary 21316

[Gary Schisler]

Re: Trailing Arm HELP!

Normally, when the runout exceeds .008-010" (8/1000ths) you will probably have some braking problems. Given Van Steels reputation, I would suggest that you check other areas to insure that you do have a problem. Do you have access to a dial indicator? Of course, even with a quality shop like Van Steel, it is possible that a bad apple slipped into the system. I had a bad rotor and ordered a replacement. After I installed it I noticed that I had worse problems. I took the new rotor down to my local machine shop and they measured .012" runout. After careful machining, I put it back on and the problem was solved.

Gary 21316

[Joe L.]

Re: Trailing Arm HELP!

Brandon----

If you, indeed, have 1/16" runout, that is WAY TOO MUCH. First, though, be certain that you have the rotors secured to the spindles with lug nuts and that there is nothing on the spindle interface with the rotor to affect a PERFECT seat.

With all of this under control, your best bet is to then dial indicate the rotor surface to determine exactly where you're at. Inexpensive dial gauges and magnetic stands available from Harbor Freight Tools will work just fine for this measurement. Assuming that you've got a good, tight bearing end play(.001-.002"), you should not have a TIR exceeding .005".

Usually, if runout exceeds this amount, the problem is excessive runout on the spindle rotor flange, not the rotor, itself. GM spindles are NOTORIOUS for excessive runout on the spindle flange.

[Joe L.]

Re: Trailing Arm HELP!

Brandon----

If you, indeed, have 1/16" runout, that is WAY TOO MUCH. First, though, be certain that you have the rotors secured to the spindles with lug nuts and that there is nothing on the spindle interface with the rotor to affect a PERFECT seat.

With all of this under control, your best bet is to then dial indicate the rotor surface to determine exactly where you're at. Inexpensive dial gauges and magnetic stands available from Harbor Freight Tools will work just fine for this measurement. Assuming that you've got a good, tight bearing end play(.001-.002"), you should not have a TIR exceeding .005".

Usually, if runout exceeds this amount, the problem is excessive runout on the spindle rotor flange, not the rotor, itself. GM spindles are NOTORIOUS for excessive runout on the spindle flange.

[Brandon K.]

Re: Trailing Arm HELP!

Thanks Joe, as always! I was considering getting a dial indicator when I saw this. I definitely think it may come in handy. Do you have the number or web address for Harbor Freight? Also, I'll remove the rotor and double check everything again today. Thanks again.

Brandon

[Brandon K.]

Re: Trailing Arm HELP!

Thanks Joe, as always! I was considering getting a dial indicator when I saw this. I definitely think it may come in handy. Do you have the number or web address for Harbor Freight? Also, I'll remove the rotor and double check everything again today. Thanks again.

Brandon

[Brandon K.]

Re: Trailing Arm HELP!

JOe,

Found Harbor Freight on the net, and placed my order already. Not bad...38 bucks for the gauge and magnetic base. Thanks again.

[Brandon K.]

Re: Trailing Arm HELP!

JOe,

Found Harbor Freight on the net, and placed my order already. Not bad...38 bucks for the gauge and magnetic base. Thanks again.

[John]

Re: Trailing Arm HELP!

Just replaced the rear wheel bearing spindles on my 75 C-3. Purchased them from Bairs in Penn.. Installed the left side rotor without any difficulty. Tried to install the right side rotor and found that it would not seat on the wheel flange correctly. It was off on one side by about 1/8 inch. Checked parking brakes and found all to be O.K... Found the problem to be that the brake drum for the parking brakes needed to cut and trued on a brake lathe because there was a ridge on the inner most corner of the drum that was preventing it from sitting flush on the wheel flange. Hope this help.Good luck!

[John]

Re: Trailing Arm HELP!

Just replaced the rear wheel bearing spindles on my 75 C-3. Purchased them from Bairs in Penn.. Installed the left side rotor without any difficulty. Tried to install the right side rotor and found that it would not seat on the wheel flange correctly. It was off on one side by about 1/8 inch. Checked parking brakes and found all to be O.K... Found the problem to be that the brake drum for the parking brakes needed to cut and trued on a brake lathe because there was a ridge on the inner most corner of the drum that was preventing it from sitting flush on the wheel flange. Hope this help.Good luck!