[s-cars] RETorquing wheels

Theodore Chen tedebearp at yahoo.com
Tue Oct 15 20:34:33 EDT 2002

--- Bernie Benz <b.m.benz at prodigy.net> wrote:
> Teddy writes:
> >
> > i'm not necessarily claiming that the loads are going high enough to
> > exceed the tension in the bolts, but they could be high enough to
> > reduce the clamping force and friction force enough for the wheel to
> > move under heavy loads.
> >
> > and as you know, you can torque the bolts only so high before the
> > bolt fails.  you could go to a stronger bolt, but then what's the
> > next weak link in the chain?  are your rotors going to warp?
> >
> And I thought maybe your posts might be getting more realistic!
> What do you think the yield torque of a 15mm fine pitch bolt might be,
> relative to the 90'# torque spec?  And what might make a rotor warp?

the comment about the rotors was somewhat tongue in cheek, since
there was a recent debate about whether overtightening bolts would
cause rotors to warp.

aren't those bolts M16?  15mm is sort of a weird size, isn't it?
if you use the standard 90% of yield for preload, that gives a
tightening torque of about 160 lb-ft, assuming 130ksi yield strength...
and the yield torque would be even higher.

for some reason, i had assumed the manufacturer had specified the
torque at the tightening torque for the bolt, but that's clearly
not true in this case.

obviously, there's plenty of room to make those bolts tighter.  so
ignore that post - i should have done the calculation first.


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