66 brake rotors

[John F.]

I'm putting new rotors on my 66 and have had a little problem getting the runout measurements within spec. I'm down to two of the four rotors that have runout readings of .005 to .008. What is an accepted method for bringing the runout in to spec? I've completely cleaned the hubs, so I don't believe there's any material interfering with the rotor sitting squarely on the hub. SSBC used to manufacture tapered shims for this purpose but they tell me that they no longer make them. I've thought about lightly grinding the inner surface of the rotor where it mates to the hub, but expect that it would be hard to control how much material is removed. Any suggestions would be very much appreciated.

John Farren

[Michael W.]

Re: 66 brake rotors

The probable source of the run out is the hubs, not the rotors. The way the factory dealt with this was by machining the two components as a set, and keeping them mated accordingly. Your best bet is having your shop do the same.

[Craig S.]

Re: 66 brake rotors

I agree with Mike - align the parking brake holes in the rotors with the flange holes and have them re-riveted and machined as a unit like original. Of course, the axles have to come out of the trailing arms to perform this operation...Craig

[Eugene B.]

Re: 66 brake rotors

Gentlemen,
I'm reading your responses with great interest. I'm getting ready to have my rotor surfaces resurfaced and wondering if I'm about to have the same problem. John, are your front rotors fine? Since they were resurfaced while riveted to the hub, I would imagine that they turned out OK? Now for the rears. If I have the shop resurface my rears, without having them riveted to the spindles, will I encounter the same run-out problem as John? By the way, what is considered acceptable run-out? If we don't want to re-rivet the rears, could they be bolted to the spindles with the lug nuts, resurfaced as one unit and eliminate the run-out problem?
Thanks guys,
Gene

[John F.]

Re: 66 brake rotors

Thanks to all for the advice. Gene - the rotors I'm using are new all the way around. I had Van Steel rebuild my T arms, and purchased new Rotors with the rebuild. The runout on one of the rear rotors is fine, less than .002", the other is .005". Van Steel claims that's perfectly OK and will not cause a problem, but my understanding is that .005 is the max acceptable runout. The new front rotors came from Corvette Central. One was fine with only .002 runout - the other exceeds spec at .008. As was pointed out, you can't determine whether the source of the runout problem is the hub or the rotor. It sounds like I'm going to have to machine at least one of these rotors to get the runout in spec. The shop manual does indicate that simply bolting the rotors on without re-riveting is fine.

John

[Michael W.]

Re: 66 brake rotors

"I'm getting ready to have my rotor surfaces resurfaced"

Why? This is probably uneccessary. Leave them alone!

"If I have the shop resurface my rears, without having them riveted to the spindles, will I encounter the same run-out problem as John? "

Riveted or not will make no difference. Riveting was done originally for manufacturing convenience and no other reason. They serve no purpose once the wheel is mounted on the car. Having them machined seperately from the hub/spindle increases the chance of inducing run out dramtically. Always machine them as a set. Better yet, don't machine them unless you have no alternative. I have over 125,000 miles on my original un-resurfaced rotors and see no reason to ever do them

"By the way, what is considered acceptable run-out?"

.005" is max but usually good shops do much better than this.

"If we don't want to re-rivet the rears, could they be bolted to the spindles with the lug nuts, resurfaced as one unit and eliminate the run-out problem?"

Yes.

[Brian Monticello]

Re: 66 brake rotors

If you remove the rivets just make sure you put the rotor back on in the same position it came off. Mark a stud or a the spindle and mark your rotor.
brian

[Eugene B.]

Re: 66 brake rotors

Mike,
Thanks for asking WHY? resurface the rotors. I am working on a car that has set for 30+ years. The rotors were very rusty and I thought that it would be a good idea to resuface and start over new. I cleaned the rotors well and ran a DA sander over the braking surface to remove the rust. Actually, they look very nice now. The more I think about it, the less likely I am to have them resurfaced. Why run the risk of excessive run-out? Think I'll just go with new pads and see how the braking efficiency turns out. Thanks again for you thoughts.
Gene

[Mike Cobine]

Re: 66 brake rotors - check bearings

What many forget is that the bearings have clearance in them. On the '63, the rear spindle is .001 to .007 inches. In a free spinning rotor, you have that to take into account also.