66 front hub/rotor run out
I had a bad hub ( race was loose in hub in outer bearing ) So I separated the hubs from the rotors and found a good used hub. I installed new timkin bearings, races and seals. The spindle looked fine. I then adjusted my bearings to spec. I had the rotors turned. I then used a dial indicator to try and get the run out on the rotor within .004. I could not. No matter which position I placed the rotor on the hub, The best I could get was .007. I then checked the run out on the hub only and the hub reads.006. I also did the other front wheel while I was at it useing the same procedure. The best I can get that side is .006. How can I get the total run out to within .004 if the hub is out more than that? Do I have to rivet the hubs back to the rotors and have them trued together? If only the side with the bad hub was out of spec I might conclude that there was some other damage to the spindle or something. But both sides are out. and the side with out the damaged hub was within spec before I replaced the bearings and races with new. Any help would be appreciated. Thanks, Bruce
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Re: 66 front hub/rotor run out
Bruce-----
Given the rather low TIR that you have (even though it's over spec), you could just rivet or bolt the rotor and hub together and then have the assembly turned on a brake lathe to get the TIR "in range". This will be the cheapest and easiest solution.
However, if it were me, I'd take the hub to a GOOD machine shop and have them true up the rotor mating surface to eliminate all runout there. Then, I'd rivet or bolt the rotor to the hub and have the assembly machined on a brake lathe. Using this sequence, you'll end up removing less material from the rotor to get TIR within specs.In Appreciation of John HinckleyComment
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Re: 66 front hub/rotor run out
Thanks Joe. That was my next question. My brother is a good machinist and I know the rotors were true and done right. If I have the hubs trued I should be able to use any trued rotor I want in the future. Is that true? ( pun intended) and can he true the hubs with the races installed?Comment
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Re: 66 front hub/rotor run out
The late model Corvette service manual has the on car brake lathe as an option to compensate for excess lateral runout. Has anyone tried this on a C1-C3 ?
Brake rotor thickness variation MUST be checked BEFORE checking for assembled lateral runout (LRO). Thickness variation exceeding the maximum acceptable level can cause brake pulsation. Refer to Brake Rotor Thickness Variation Measurement .
Brake rotor assembled lateral runout (LRO) exceeding the maximum allowable specification can cause thickness variation to develop in the brake rotor over time, usually between 4 800-11 300 km (3,000-7,000 mi). Refer to Brake Rotor Assembled Lateral Runout Measurement .
Review the following acceptable methods for bringing the brake rotor assembled LRO to within specifications. Determine which method to use for the specific vehicle being repaired.
If the assembled LRO cannot be corrected using these methods, then other components must be suspected as causing and/or contributing to the LRO concern.Comment
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Re: 66 front hub/rotor run out
Bruce-----
If you have true hubs and true rotors (rotor disc pad surfaces true to hub/spindle mating surface), you should be able to assemble the two and be within GM's TIR spec. You might not end up at "0" TIR, but you should end up well within spec.
Originally, I don't think that GM really cared too much about the TIR on the front hubs or rear spindles. They riveted on an UNFINISHED rotor and then machined the whole assembly to finish thickness and TIR. They had the advantage of of starting with an UNFINISHED ROTOR; you don't. I have found that most GM hubs and spindles to be WAY, WAY out on TIR.
You definitely want to have the hubs machined with the races installed and COMPLETELY SEATED. Don't ignore those last 2 words or you'll be wasting your time.
By the way, you will find that most SERVICE rotors (just the rotor and not the complete hub and rotor assembly) will be very true right out of the box. Of course, those which include riveted rotor and hub will be true, too, but they're a lot more expensive and much harder to find. GM discontinued them years ago.In Appreciation of John HinckleyComment
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Re: 66 front hub/rotor run out
Hi Bruce:
If you can have your brother true the hubs, that would probably be the best approach. Alternatively, you can try shimming the rotors. Some people make their own shims, but a company called Brake Align (http://www.brakealign.com) makes some nice ones.
The main problem is that these shims are expensive when purchased in small quantities. I purchased a small assortment when I was doing my brakes, and I have a few left over. Contact me offline if you would like to try them.Comment
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