Here's another hold-down idea for guys who end up replacing their car's Rotors due to warpage/wear/etc and want a quick way to fasten new rotors down (once they have the run-out set.

I was going to do a couple different things incl installing new rivets, then drilling/tapping the hubs and using tapered screws. I even made a bunch of rivets, but I hate to have them permanently fused to the hubs. Plus, the holes on my car's hubs are somewhat not drilled perfect, so tapping them straight might not go so well. Anyway I ended up going with 1/4" furniture screws from the hardware store. See picture below. The "nuts' of the furniture screws fit perfect through the rotor holes and protrude into the holes of the hubs, which centers and kind of 'locks' them together. You can see in the picture I had to shorten the 1/4 bolt and cut some new threads back to the head. But that was easy.

So its not as good of a solution as tapping the hubs and using larger stainless steel screws like I've seen, but it's *another* idea if the original holes in the hubs were drilled-out 'wonky' like mine. The primarily job of the rivets/screws is to secure the rotor to the hub esp when the wheels are off. The main downfall of this 'system' is a guy will need to pull off the hub to get a hex socket onto the backside to remove the bolts. But that's one castle-nut and I'm hoping I won't have to touch them after they're installed.

 

Note: the hardware above is brass-coated steel, not brass. (the rotor/hub will get painted cast paint soon)


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Very Interesting! Do you have a picture of the back/inside where the furniture screws protrude thru?

 

I can take a pic (in a bit). It looks like the back of the hub with the hex screw.

 

Interesting, first I saw those used. I've been tapping and bolting on rotors for decades, works great.

 

I agree. Tapping/drilling is a better way to go. That would be my preference too. I don't generally like to go the half-assed route. But some of the holes in my car's hubs were drilled oblong ..so I wasn't sure how easy it would be to tap them 'centered'.

I'm glad I didn't rivet them though. After I got the rotors bolted to the hub the run-out increased a bit. I had to go back and remove the paint I put on the hub. In the end I was able to get them back to a .0005" run-out.

Backside:


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We used to call those sex bolts.
Looks like this will work well, but are they really even needed??

 

Probably not needed.

More of a convenience for me. I mounted the knuckle in the vise and got the rotor run-out tolerance real tight and don't want to risk getting any debris between the two at some point down the road that might throw it off.

A 'tight' rotor run-out also means a 'tight' wheel run-out too, and potentially less car shimmy (smoother ride). If a car has a rotor run-out of, say, .002" at it's edge (due to a poorly-machined hub flange), the wheel mounting surface will also have run-out (assuming the rotor was machined right). Whatever the run-out is it'll be multiplied at the outer edge of the tire. In fact it can be significant. Perhaps 1/8" or more, depending on the run-out amount. I put the knuckle in the vise and mounted a wheel (quite a while ago) and I was pretty surprised how much movement there was. If all the wheels are wobbling 1/8" in/out as ya go down the road, that can translate to vibration, even if it was the best tire-balance-job there is.

I'm assuming that GM after riveting on the rotors, and turning them (on the hubs), also machined the rotor face too (???) And then inserted the wheel studs. Otherwise the C3's would be like a clown-car going down the road with wheels wobbling! LOL

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Easier than tapping and counter-sinking, seems like it'll do it's job. I'd definitely want to add some loctite to them, although having one of the rear ones come loose could result in some Mustang level excitement leaving a cars and coffee event
M

 

Nope..I actually put anti-seize on the bolt threads. There's enough friction on the bolt and nut faces, and tension on the bolts, they won't go anywhere. And worst case, if they did, they'd just fall out the inside. They're not going anywhere.

I got the second hub/rotor mounted today. About .0002" run-out ..pretty close to zero for all practical purposes. Pretty satisfied with that. No shims. I had machined the hub faces a while ago. A lot of wasted time though. If I was doing it over again, I'd go buy new hubs for $500/pr ...lol. Assuming they're machined 'right'. Now on to the next thing....

 

.0002" is exceptional, anything under 003" is good. That's a very good dial in.

It would be interesting to see how those bolts come out after you have them locked tight. With the flatheads they are very tight, no Loctite needed. In fact, if I don't put never seize on the taper they might not come out.

 

I thought you (or someone) was using SS screws? I don't plan to take these out. But they'd probably twist off pretty easy if needed to. They're probably grade-0. LOL Like I mentioned originally, I wouldn't say this is the 'best' way ...it's just 'another' way.

 

No, I never use SS flat heads, too brittle.