The reason is that it's less expensive to manufacture wheel bolts than studs and nuts. I put threaded studs on my 82TQC and I modified Porsche alloy wheel nuts to match the Audi Shape.
From: Graydon D. Stuckey[SMTP:email@example.com]
Sent: Tuesday, February 13, 1996 11:55 AM
To: G. Erickson
Cc: Quattro list
Subject: Re: Wheel studs?
On Tue, 13 Feb 1996, G. Erickson wrote:
> It might be worth it put up with those infernal wheel bolts. I
> had it explained to me one time that the wheel _bolts_ are self-torqueing
> due to expansion/contraction or centifigal force or some such.
> The opposite side being that the wheel _studs_ tend to loosen
> their nuts over time.
> If this is indeed true, then I'll happily put up with the
> occasional nusience (sp) of dealing with the bolts if I know that I don't
> need to worry about them loosening and falling off.
I have never heard that before. In fact, every race car that I
have ever seen that was not allowed to use a single knock-off style wheel
nut, has had studs not bolts. Granted that is also done primarily for
convenience, but I don't think they have a tendency to loosen
I have replaced bolts with studs on a couple RX7s with never any
loosening problems. Mind you, I check them alot, because I change them
alot at autocrosses. Most every other car in the whole world uses studs,
so I don't know why VW/Audi and Mazda can't figure it out.
Maybe someone else has some further input?
Graydon D. Stuckey
Flint, Michigan USA
'86 Audi 5000 CS Turbo Quattro, GDS Racing Stage II
'85 Mazda RX7 GS 12A-leaning-towards-a-13B-soon