Wheel bolt grade

Ti Kan ti at amb.org
Tue May 11 20:05:00 EDT 2004

All this talk about getting lug bolts from hardware stores, etc.,
I want to bring to everyone's attention that the bolt seat shape
must be correct for the wheels you have.  This is an important
issue, above and beyond the size and pitch of the thread.

Most (all?) Audi OEM wheels require bolts with ball-shaped seats,
whereas many aftermarket wheels need cone-shaped seats.  If the
wrong bolt type is used there is danger that the wheel would
come loose even if torqued to the correct spec.

The bolt length must also be correct.  Too short, and there is not
enough "bite" into the hub and the bolt could also loosen over time.
Too long, and the bolt would protrude into the hub and rub on
other parts (suspension, brake, etc).  If you switched to aftermarket
wheels with a thicker bolt mounting surface, or if you use wheel
spacers, the bolt length must be increased or there will be a reduced
number of turns into the threads.

For those who converted to lug nuts, these are also important to
consider, except now the bolt length is now a part of that which is
attached to the hub, and the nut has the seat on it.

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