[s-cars] Re More on Wheel Torque

[Trevor Frank]

Yes, and yes.  One way to "torque" con rod bolts is to use a micrometer
and measure stretch.  Get yourself a set of Carrillo rods and in the
instructions is the amount of stretch and a guess on torque, wet torque
I might add.  If someone really wanted to you could measure the stretch
of a bolt dry then torque it wet to correlate to the stretch of the dry
one.  Although dry torque tends to vary a lot, so get yourself some
really clean bolts and check the threads really well.  In fact based on
the bolt strength there are usually specs on torque, generic ones, that
basically are correlated to a certain amount of axial stress in the
bolt.  This is often either at or up to 30% lower than the yield
strength of the bolt.  This is a recommended max so you need to look at
the application but it can be done.

If you know the lubricant you can do a calc for dry to wet, I think
Scott just did this with his 80-110 remark.  There are guidelines for
this based on lubricant used and bolt material/base material, basically
a multiplier to the specified torque, like .xxx * dry torque =
equivalent torque wet.  Although often is isn't that simple.

Machinery's Handbook has a decent section on fasteners and threads,
calculating torque and Coefficient of friction with different
lubricants.

Refreshing my memory I came across this info in the Machinery's
handbook.

Accuracy of bolt preload Application Methods.

By feel +-35%
Torque Wrench +-25%
Turn-of-nut +-15%
Preload indicating Washer +-10%
Strain Gauge +-1%
Computer controlled Wrench below yield (turn of Nut) +-15%  Sunnen has a
nice one of these for a few k or so.
Yield-point Sensing +-8%
Bolt elongation +-3-5%  This is what we where talking about, stretch.
Ultrasonic sensing +-1%

In my opinion the bolt/nut on the wheel is not very highly stressed so
the inaccuracy of tightening it with a torque wrench is really no big
deal.  I also use antiseize for all of the usual reasons.  Porsche's
alloy nuts got me started with the practice.  I think it is also a good
way to keep your threads in good shape.  We could debate, although I
won't, that saving your threads by using antiseize is better prevention
than worrying about the extra torque but consistent torque that you get.
This is because as you degrade the treads your friction goes up and your
axial stress at a given torque goes down.  Just one mans thoughts.

-----Original Message-----
From: Ian Duff [mailto:iduff at rcn.com]
Sent: Thursday, October 24, 2002 6:29 AM
To: QSHIPQ at aol.com
Cc: s-car-list at audifans.com
Subject: RE: [s-cars] Re More on Wheel Torque


WTF are "2 piece nuts"??? The only time I've seen anything remotely
resembling "2 piece nuts" is after some infraction at home.

It seems to me the argument against using antiseize is a "wet vs. dry
torque" argument, not an "antiseize will encourage the fastener to
automagically loosen itself" argument. The intelligent discourse so far
(thanks, kids, for not getting personal, except for one blast from an
un-named erstwhile cameraman) has seemed to endorse antiseize as perhaps
promoting fasteners retaining tension a bit more effectively, as well as
allowing their removal, like for lugs after a winter of salted roads.
This investigation seems to be centered on wheel lugs and wheel to hub
mating faces primarily, and pretty explicitly NOT on spark plugs.

Is there such a thing as a conversion from dry to wet torque? My guess
is no, since there could be way too many variables. I'm guessing that
applying a measured amount of torque to a fastener is an indirect way of
measuring fastener stretch, which might be a direct way of measuring
clamping force. Am I close yet? If so, might it be possible to install a
lug bolt dry to the specified torque, measure the stretch, remove it,
select and apply an antiseize compound, and re-install with a torque
wrench until the same stretch was achieved? How does one measure
fastener stretch? Micrometer? Are thousandths of an inch sufficiently
accurate? Is measuring overall length of the same bolt dry vs. wet in
the same hole good enough?

Given that my track time has yet to occur, and is unlikely to do so in
the near future, my need to torque after every run group is improbable.
I feel it necessary to check torque every now and then, just as I do to
check tire pressures. However, when the time comes to change a wheel,
the "graunching" as I tighten the lugs makes me think that the torque
I'm applying, even thru a torque wrench, might be affected by whatever
is causing that horrendous noise. BTW, how or where does one get their
torque wrench calibrated?

-Ian Duff.
-----Original Message-----
From: s-car-list-admin at audifans.com
[mailto:s-car-list-admin at audifans.com]On Behalf Of QSHIPQ at aol.com
Sent: Thursday, 24 October 2002 08:36
To: wolff at turboquattro.com; s-car-list at audifans.com;
quattro at audifans.com; urq at audifans.com; 200q20v at audifans.com
Cc: mlped at qwest.net; jolly at zoomtown.com
Subject: [s-cars] Re More on Wheel Torque

<<lots-o-good-stuff snipped>>

Another anomoly (scarey) that appears to need clarification.   The 2
piece
nuts are considered the best for torquing wheels (hey I have those on my
4 runner), and the specification for most of them is to lubricate the
nuts. Further reading indicates this to be lubricating the 2 pc nut
itself, NOT the threads/land/ or studs.



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