Grant Edwards > wrote:

>On 2004-12-13, Lanny Chambers > wrote:
>> In article >,
>> Grant Edwards > wrote:
>>
>>> Since they're supposed to bear most of the weight of the car,
>>> I would think that one would want metal ones.
>>
>> They don't bear any weight at all.
>
>If so, there's a _lot_ of misinformation being spread by people
>(including wheel manufacturers and car mags). According to
>Ronal USA's web site:
>
> "A hubcentric fitment, is one where the interior of the
> backside of the wheel - referred to as "centerbore"-is an
> exact fit to the "hub"-that protrudes from the mounting
> surface of the wheel. The relevant issue here is that the
> WEIGHT BEARING of the wheel on the car is done on the HUB
> when it is "mated" to the wheel! This has to be an exact
> fit. The LUG NUTS, simply affix the wheel and hold the
> wheel to the car and do not affect load bearing."

Reading this, I have to think Lanny's assesment is on the dot.
We are going to put the weight of the car on soft, fatigue
sensitive, aluminum or plastic? Seems more ridiculous than
Teddy Bears as wheels.

>According to Sport Compact Car magazine:
>
> "Hubcentric wheels have a hole at their center that fits
> closely over a round feature on the hub, serving to center
> the wheel on the axis of the spindle, as well as bear the
> vertical weight of the vehicle.

I have had trouble before with ridiculous claims originating
from SCC in this group. I forgot the exact issue, but they
still have zero respect in my book.

> The wheel bolts or studs
> then serve simply to hold the wheel onto the hub, and are
> loaded only in tension, where they are strong. If the studs
> were required to absorb vertical forces, they would be
> loaded in single shear, the weakest arrangement for any
> fastener."

This is another example of plain stupidity. Fasteners, like
bolts and rivets in aircraft skins, are *very good* in supporting
"vertical" (sideways) forces. As long as they are tightening
down sheared parts that prevent bending moments on the bolts.
And the friction between the parts helps too. While I would assume
nowadays all modern planes are glued together, in the old days
the skin panels were *riveted together*. (I did various labs
manufacturing them and computing their strength as an undergrad.)
The skin panels are in tension (sideways force.) And no, the
aerospace industry does not deal with ineffective components.
(Always excepting Air Force 1, of course.)

>> All they do is help center the wheel until you can get the
>> lugnuts on, and plastic works fine for this trivial task. The
>> lugs carry 100% of the weight.
>
>I think you're quite probably correct, but there sure is a lot
>of misinformation out there...

I think you are right on. And somehow, it always seem to be the
same originators.

Leon

>> You can leave the hubcentric rings out with no ill effect.
>> Just observe the normal lug tightening sequence: run them all
>> up finger tight, then torque them in two steps, in a diagonal
>> pattern.
>
>A set of rings is only 10-15 USD, and it seems like good
>insurance.

--
Leon van Dommelen Bozo, the White 96 Sebring Miata .)
http://www.dommelen.net/miata
EXIT THE INTERSTATES (Jamie Jensen)