The torque on threaded fasteners is extremely critical to get the
maximum strength out of them. Wheel lugs and bolts are usually designed
to be installed dry as friction is part of the design to keep them from
loosening. When a bolt is assembled, there is a "clamping" force that is
applied to the parts being clamped and some combination of the bolt
being stretched or the part being crushed keeps it all together. When a
fastener is lubricated, much less torque is required to achieve a given
clamp load. In general, when using loctite or oil, the torque should be
reduced by ~20%. If using an anti-seize, 40-50%. Failure to reduce the
torque does the same damage as over-tightening. Lubricating the threads
and the lug seat will both have an effect on the actual clamping force.
In addition, the clamping force will change as the nuts or bolts are
reused. ~70% of the forces applied to a nut are carried by the first
three threads. As they deform, the clamp load and required torque will
change. Fastener experts teach that unless a nut is specifically
designed to be re-used, it should only be used once. I've seen the
variations demonstrated with clamp load testers. So if you really want
to make sure the wheels are installed properly, lug nuts should be
changed after 3-5 uses.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
Of Jfp w/2 wbxs
Sent: Thursday, July 25, 2002 11:24 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Lug nut madness

Hi All,

I once had new radial R tires installed on a '79 loaf and insisted on
standing by the tire replacement action (brought my own safety glasses).
I
mentioned to the installer that I wanted a torque wrench used to tighten
the
wheel nuts and he said "OK, no problem". A moment later I swear I heard
his
ask a workmate, what's a torque wrench???? I immediately took up the
issue
with the service manager and they found the shop's torque wrench and
used
it. Was the tool even accurate? When I got home I loosened and retorqued
the
wheel nuts with MY torque wrench.

While it is espressly discouraged by VW, I put a SMALL amount of oil on
the
threads before torqueing wheel bolts or nuts to be sure the applied
torque
is reached evenly on all wheel fasteners. 133 ft. lbs. to one wheel bolt
may
only be 100 ft. lbs. to the next due to corrosion. Any pneumatiic
overtightening is the work of untrained laymen usually working flatrate.

Regards,     John

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