[s-cars] RETorquing wheels

[Theodore Chen]

--- QSHIPQ at aol.com wrote:
> >i'm not convinced it's heat cycling.  i think your bolts may be exhibiting
> >classic signs of fatigue.  they were stretching permanently, causing the
> >torque to drop.  if i were you, i'd replace all of them immediately.
>
> Maybe.  I doubt it, but maybe.  Thinking about all the folks that own audis
> that consider a bolt a lifetime part Teddy.  IME, usually in a "fatigue"
> state, a bolt won't pass thru a die cleanly.  These do.

yes, that is true.  maybe it's your wheels, as bernie suggested.

> I also swapped the
> front bolts for the rear bolts, the rears were at spec when I did so, and
> remained at spec thruout my experiences with the front.  This also wouldn't
> explain the fact that after 4 retorques, all subsequent cks indicated no
> change.

the rears are more lightly loaded than the fronts, so that by itself
wouldn't necessarily tell you anything.

also, bolts don't necessarily keep right on stretching until they fail.
in some cases, they stretch and at some point, they stop stretching.
and eventually they fail.  work hardening, perhaps.

> >are your spacers hubcentric?
>
> No, the wheels are, the spacers aren't.  FYI, we use these same ones in the
> rally car without incident (knock knock).

does the rally car run the same bolts/studs?  does it run on dirt?

> > do they provide a flange for the wheel to
> >pilot on?  are they doweled or screwed to either the hub or the wheel,
> >to eliminate a shear plane from brake/drive torque?
>
> The wheel rests on the hub, not on the spacer or the wheel bolts.

how thick is this spacer?  it sounds like your spacer isn't very thick
at all - in which case it's probably not so much of an issue.

> >the bolts/studs are
> >not meant to bear the weight of the car.  they're supposed to be loaded
> >in tension and in shear (against brake/drive torque).  and some
> >manufacturers will have you screw the rotor to the hub to eliminate shear
> >loads on the bolts/studs.
>
> I'm not aware of that at all.  Many a Volvo and VW have a single set screw
> that keeps the rotor holes oriented to the hub holes.  That set screw can't
> take any sheer load, it wasn't meant to.

most cars don't have anything at all, and rely on clamping and transmitting
the loads through the roots of the studs.

> >i really don't like spacers for the above reasons.
>
> I've never liked them.  But the wheels won't fit over the brakes without
> them.  That said, in this case, the spacer isn't THE problem.  I believe this
> was a force majeur due to just the right combination of factors, including
> weather and a lot of right turns.

it sounds like you're using a pretty thin spacer if the wheel is still
able to pilot on the hub, so i can see your point.

something happened.  the question is what.  i'd still suspect the
spacers - even if they weren't a sole cause, they likely contributed.

> I'll replace the bolts, cuz I have another set.  In no way will I consider
> that to be enough.  I have no choice on the spacer, so they have to stay for
> a while.  Tho I appreciate you taking the time to think on this a while, I'm
> still convinced this can "happen" if conditions are right.  Even with all
> your preventive ideas above, in the end, the bottom line remains the same:
> Routine cks of wheel bolt/nut torque in a performance theatre is the best
> medicine, and really, the simplest of solutions.

yes, i agree.  drive it like a race car, maintain it like a race car.

sounds like you have a brake clearance issue, which is why i ran spacers
before.  i was trying to use 16" wheels with 13" brakes.

have you ever run those wheels without spacers?  are other people running
the same wheels without spacers?  in this situation, do the bolts need
to be retorqued frequently?

> I'm only putting all this up to make folks aware, not speculate on the
> failure.  Anyone that knows me, knows I own a plethora of torque wrenches,
> and use them often.  And this still happened.  What I'm more concerned about
> is the high percentage of track attendees that don't even own a torque
> wrench.

everybody should own a torque wrench.  even a cheap torque wrench is
better than no torque wrench.  you can take a cheap torque wrench and
compare it to a known good torque wrench for a specific torque value.

-teddy


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