Jim, Mike, et Listers,
Jim and Mike have weighed in with some arguments favoring replacing the
7/16" studs with the original diameter in favor of going to 1/2" diameter.
Perhaps the first great Tiger List controversy of '99 has begun?!?! Since
I'm the one who suggested going to 1/2" diameter studs, I feel compelled to
make a few additional comments. First, an historical comment; When I first
bought my Tiger in 1970 I also found the wheel studs to be severely
stretched, probably a combination of lousy British steel and the careless
use of an impact wrench. Since I had to replace them anyway, going to 1/2"
diameter seemed the logical if not fully considered choice. I don't,
however, recall having any problem the one time I've used the spare tire in
the past 28 years. Probably not the ideal fit, but good enough to get us
from just south of Carmel to a tire store in Monterey, so this may not be a
totally valid reason to stick with 7/16". Also, I assume the unsprung
weight argument is tongue-in-cheek.
Jim, I've been told by my engineering friends that all you need to achieve
the maximum strength of the bolt is a thread depth equal to the diameter of
the bolt. Now, I feel better having a bit more than this, but it doesn't
seem likely that drilling out the nuts to achieve yet another 1/4" is going
to add any strength. It does, however, insure that you neither bottom out
because of too long studs, or hydraulically jam the nut if you apply grease
to the threads (a no-no with closed end nuts).
Again I say, for all the work required to replace the studs of either
diameter, the choice is really pretty arbitrary. If one chooses 7/16", then
use at least grade 8 or ARP super bolts and be extra careful not to
over-torque them. With either 1/2" or 7/16", a major point is to get the
interference fit between the knurled portion of the shank and the hub holes
sufficiently tight. This might be harder to achieve if you replace with
7/16" studs.
Bob
At 07:35 AM 1/3/99 -0500, TIGEROOTES@aol.com wrote:
>Mike,
>When Bud Bohrer had aluminum Tiger front hubs manufactured, I bought a set. I
>installed the ARP 7/16" studs. I put the mag-style lug nuts on my lathe,
>drilled thru the heads, tapped them and gained over a quarter inch of threaded
>contact between the studs and nuts. I left the studs at full length so if I
>choose to use a wheel with a thick center or spacers there will always be
>plenty of stud. The original studs on my Tiger had stretched, and this could
>be seen visually! I don't recall reading in the PDR that SCCA requires
>anything special regarding wheel studs...but it is a good idea. I think
>installing 1/2" studs on a 2600 pound car is overkill, and all it really does
>is increase unsprung weight x 16 studs.
>Jim Leach, Seattle
>
>PS: If anyone has an extra set of Tiger rear hubs available, I would like to
>have a set!
And previously:
>If you choose to use 1/2 inch studs, you will have to find a wheel with 1/2
> inch stud holes for your spare tire. The ARP 7/16" wheel studs have an
> extremely high rating, certainly adequate for a small car. They are also
>very
> long and unless you like the Nascar-look, will need to be shortened.
Also, Mike Wood wrote:
>Many agree that going to 1/2" studs is not worth the trouble, others like the
>extra margin of safety. For a street driven application, I don't see any
>reason to go to 1/2".
>If the car is to be raced, open tracked, autocrossed frequently, it probably
>makes sense to install long 1/2" studs, use longer lug nuts and leave 3-5
>threads exposed on the back side of the lug nuts: just like NASCAR, SCCA and
>NHRA require.
>Mike
Robert L. Palmer
Dept. of AMES, Univ. of Calif., San Diego
rpalmer@ames.ucsd.edu
rpalmer@cts.com
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