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newrider3
newrider3 Reader
8/10/20 9:06 p.m.
Curtis73 (Forum Supporter) said:

Without the proper hub bore, the lugs are holding it on, up, left, right, in, out, and everything.  The only thing preventing a pothole from snapping the lugs is the clamping force of the wheel against the hub... but honestly, I've never seen it become an issue, other than pretty massive impacts that would rip any wheel off.

Because the clamping force is the only thing that matters, and the only thing holding the wheel on in any case. The wheel studs do not support the wheel in a shear direction, and are not designed to do so.

 

Let's do some maths.
T=KDP; T=torque (in-lbs), K=friction constant (0.2 for dry steel), D=bolt diameter (inches), P=bolt clamping load (lbf).

Choose some arbitrary easy numbers. 0.5" wheel stud torqued to 100 ft-lbs, you have 12,000 lbf clamping. 5 lug wheel, 60,000 lbf total clamping. Depending on the size of the hub face and wheel face, say 2000 to 3000 psi at the interface area?

irish44j (Forum Supporter)
irish44j (Forum Supporter) MegaDork
8/10/20 9:11 p.m.

not important, as long as the wheel center bore is larger than the hub center bore. The centerbore isn't supporting weight, it's just there to help you put the wheel on. If you torque your lug nuts in the correct pattern and torque (and you're using acorn-style nuts that self-center), the centerbore isn't actually doing anything.

Our track e30 has never had wheels that match the centerbore and has never had any issues with vibration. Just do your lugs right. 

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
8/10/20 9:53 p.m.

In reply to newrider3 :

Indeed.

 

If a bolt fails in shear, it's because it was left loose.  Bolts are really, really stiff springs and the proper torque is merely tensioning the spring to a point higher than any expected loads. 

 

This is a point I tried to hammer into peoples' heads when they were trying to make RX-7 suspensions work more flexibly by using Nylocs on the bolts and leaving them loose.  Bolts are far weaker to shear loads than they can handle from tension loads!

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
8/10/20 9:55 p.m.
Jesse Ransom said:

I thought there were a couple of different conical lug angles?

EDIT: A quick search suggests there are both 45 and 60 degree seats/lugs.

45 degree is generally only seen for circle track wheels.  I assume that between the shallower taper, and the much larger (1" or so) hex, it makes it a lot harder to rip a steel wheel off over the lugs.

z31maniac
z31maniac MegaDork
8/11/20 6:21 a.m.
NickD said:

I ran my Miata hard for two years without centering rings. Never broke a wheel stud or had any catastrophic failure. Put them on this year, because it seemed the responsible thing to do. I can't tell any difference in how it drives and it really didn't make it that much easier to install the wheels. Also, nearly had them bone me, when I went to swap wheels and tires at a track and the one spacer wedged itself to the center bore of the hub and had to be essentially chiseled off.

Anti-seize bromontana, anti-seize. I always put it in between the hub ring and wheel, and between the wheel mounting face.

Of course, it was also on the studs since I was using ARP with 949 on the Miata, and Vorshlag studs and I forget which lugs on the E30s.

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