[s-cars] More questions about wheels and tires

[Theodore Chen]

--- Igor Kessel <igor at s-cars.org> wrote:
> Matthew Farr wrote:
>
> > 3. What do I need to know about "hubcentric wheels" to make sure that I
> > buy wheels that will be correct for my 1993 S4?
>
> You need to have them perfectly hubcentric, to Audi spec (what's that,
> 47-point-something mm? - don't remember this offhand) or  you'll turn
> your Audi into a rapidly self-destructing industrial gravel compactor.

to expand on this, hubcentric means that the bore in the wheel is
sized to fit snugly over the flange on the hub.  this ensures that
shear loads (from the weight of the car) are supported by the hub
rather than the wheel bolts.

if you don't use hubcentric wheels, the wheel bolts must support the
weight of the car in addition to providing clamping load to keep the
wheel attached to the car.  this introduces significant bending loads,
most likely through the threaded portion of the bolt, and worse, the
bending load is fully reversed twice for every revolution of the wheel.
the audi is a heavy car.

in short, you should definitely insist that the wheels be hubcentric.
don't let the salesman talk you into wheels that aren't hubcentric,
even if it's a good deal, unless he's willing to provide you with spacers
to make the wheels hubcentric.

-teddy


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