Scott MacDonald

Who was the engineer smoking crack when they designed this setup. Im sure most of you are aware that the front rotors are "riveted" to the hub. To replace the rotors, the rivets must be removed by drilling them out or cold chisel the heads off. Then to replace the new rotors it is recommended that you countersink the back of the hubs to accept a tapered head machine screw so it sits flush with the back of the hub, then tap the rotors so you can screw the machine screws into the rotors to re-attach. Maybe it's just me, but it seems as though the only real purpose for the rivets is to position/orientate the rotor to the hub. The five wheel studs actually provide the clamping force to hold the rim to the rotor and the rotor to the hub. There has not been a real valid reason to physically attach them together, other than so GM could charge more for the while assembly back in 79.

So, I am about to replace the rotors on my vette, as reference, no other vehicle I have ever worked on, is set up like that. The rotors are not mechanically attached to the hub except by means of the studs for the wheels. I will remove the rivets as required, but on re-assembly is it necessary to re-attach with new rivets or the above mentioned tapping and screwing together. It really seams to be a colossal waste of time and an unnecessary step. Since replacement rotors are within specs for runout and are centered onto the hub through via the studs and assuming the mating surface of the hub to the rotor have no excessive runout, re-attaching the hub to the spindle and then the rotor to the hub should be as effective as it is on todays cars and trucks. right?

Can anyone give me a good reason why the hub & rotor need to be physically mated before reinstalling onto the spindle. It just seems that everything on these cars was an exercise in engineering taught by Rube Goldberg. What ever happended to keeping it simple?

Oh, yeah, is there a modern replacement for the 79 hub? Does GM make a similar hub that would replace the rivet version? Has anyone ever looked into this?

Any feedback is greatly appreciated.

Scott

sstopczy

They were mated for production purposes. No need to rivet the new ones on, the lug nuts will hold it in place.

damoroso

Maybe everything else you've worked on has "floating" calipers. C3's don't. The rotors were fixed to the hubs for runout purposes. And, since you have fixed calipers, if you have excessive runout, you'll end up with air in the system. Also, these rotors aren't the throw-aways, (consumables) that newer vehicles have on them. They don't usually wear out very often and as such, these things don't typically need to be replaced unless someone was a complete chuckle head. Since we're dealing with 30-40 year old cars, who knows what was done to them in the past.

Mike Ward

Sure- do a LOT of reading on HOW and WHY C2/C3 rotors and calipers are different from every other car you've worked on. Make sure you include the word runout in your search.

lionelhutz

I wouldn't just assume they're within spec.

I bolted the hubs and rotors together and chucked them into a brake lathe for Dad's car. 1 was very good. The other took 2 passes to make true.

Mike Ward

Even if the new rotor is dead flat and has zero runout- that doesn't take care of the hub which was not machined true in the first place.