Wheel Adapter/Spacer nuts. . .hex nuts or 12-pt. nuts???

[atomicjoe23]

I'm going to be machining a set of front/rear adapters for my new wheels (17" x 9" ZR-1 5-spokes on a 1967 Pontiac Firebird. . .I haven't measured on my car to verify yet, but I believe they will be an ~ 1.7" thick front spacer and an ~ 2" thick rear spacer based on what information I have gathered from others running these wheels on first-gen F-bodies) and I was wondering if it made a difference what style of nuts I ran on the spacer.

The spacers will be hub centric, I'm using ARP 1/2-20 studs and nuts; I've got a couple of trains of thought here. . .



First train of thought is that the 12-pt. nuts have a smaller flange and therefore would require a smaller counterbore so the adapters would retain more material.

Second train of thought is that the the hex nuts larger flange means there is a larger bearing surface for the nut and it may be a more secure joint. Also, since the counterbore will be larger more material is being removed and the adapters would be lighter (even if only marginally).

Third train of thought. . .I'm putting WAY too much thought into this. . .

Thanks for the input.

[astroracer]

As far as the spacer goes I wouldn't worry about making it hub-centric. If you have the capability to machine the 60* included angle for a tapered seat lugnut THAT is how I would do it. Use a regular set of lug nuts to hold the spacer on and the tapered seats locate the spacer.
Now, as far as putting that almost 2" thick spacer on the front I wouldn't do it. You have to realize the front spindle bearings are not designed to carry that kind of cantilevered, off center load. You may get away with it for a while but it will shorten the lives of the bearings. Just something to think about.
Mark

[atomicjoe23]

Astroracer. . .machining a 60* seat for the tapered lug nut is cake; I've got a NICE Niagara end mill just for that, but making it hub centric is no more work than not making it hub centric. . .it's just hitting a dimension on the central bore. I work with .0001" tolerances for my day job so hitting a very slight clearance fit is cake and that takes a side load off of the wheel studs so all they are doing is holding the wheel to the hub instead of holding the wheel and locating the wheel. The less work any one piece has to do the better off it is. . .

. . .as far as adapters go the need for the extra thick spacers is because of the high offset rims; I've done quite a bit of reading (on this forum, Lateral-G.net, and others) and the spacer is necessary for a high offset rim. . .

The spacer actually puts the wheel centerline closer to the bearings and reduces the load on the bearings compared to a high offset rim without a spacer. . .at least that's the theory and seems to be the general opinion on the matter. These are the same wheels that Mark Steilow has/had on the Red Devil and there are a TON of first-gen F-Bodies running this combination both on and off the track.

Now I said that was the theory and what I read because I haven't set it up on my car yet. . .once get my Kore3 billet hub and rotors I will be able to measure and see how thick of an adapter I need and how that will actually load the bearings, but running the correct spacers would be no different than ordering a set of tires with a custom backspacing. I may very well decide that isn't the case once I can see exactly what I am dealing with instead of just reading about it. . .

Something I didn't mention is the current spindle and hub set-up is only temporary. I will be upgrading to the forged aluminum ATS AFX spindles with the larger C6 bearings. . .probably next year; parts of the current set-up are affordable parts that are temporary to get the car on the road and allow me to enjoy it while I save money for the premium, expensive parts.

[astroracer]

Well, it's good to know you are on top of what you are doing. Sometimes you have to point out the issues to get a feel for how much a guy really knows.
If you can do the tapered seats do that along with your hub-centricity. Then there is no issue with lug nut selection. Any regular nut will work. Shot us some pics when you get started.
Mark

[atomicjoe23]

Will do. . .as soon as my Kore3 billet hubs and my rotors show up I can take the measurements and get started.