More on audi wheel bolts/studs/torque

Bernie Benz b.m.benz at
Mon Oct 21 15:48:51 EDT 2002

What do you mean when saying "10.9 bolts can be stressed if the threads
themselves lose the cold rolled tempered edge and sharpness"?  Of course,
all bolts can be stressed, including 10.9 with rolled threads.  Audi's
recommended wheel bolt torque is way below the maximum allowable for this
bolt in bolted flange applications, restricted by the aluminum wheel

Bolt and flange luberication has at least two advantages in this
application.  It prevents water intrusion and thus corrosion of both the
wheel to hub interface and the threaded bolt to hub interface.  Galvanic
corrosion because of dissimilar metals is a serious problem for this
application in your "rust belt" enviroment.  Further it will give a much
more consistant and higher clamping force for a given applied torque than
will a dry joint.  To achieve similar consistancy, a dry joint must be
totally degreased after chasing with a tap and die, respectively.  Why are
head bolts lubed?  To apply a larger portion of the applied torque, limited
by the bolt's uptimate strength, to clamping force and less to overcoming

As a wrench for hire with concerns about liability and no specific direction
from Audi, your delema is do you go full clean and dry, leave 'em dirty, or
lube them well??  Not my problem, so I've always lubed them.


> From: QSHIPQ at
> Date: Mon, 21 Oct 2002 15:32:58 EDT
> To: b.m.benz at
> Cc: 200q20v at
> Subject: Re: More on audi wheel bolts/studs/torque
> --
> [ Picked text/plain from multipart/alternative ]
> With you on the jam nut idea Bernie, it's not practical in application, nor
> the problem.  WRT replacement....  I spoke with several Metric fastener guys
> in the past few months.  10.9 bolts can be stressed if the threads themselves
> lose the cold rolled tempered edge and sharpness.  dirt and corrosion are the
> enemy here.  With very infrequent service intervals, I've actually
> experienced hub thread failure on customer cars just pulling the bolt out of
> the wheel.  All should know that audi hubs are expensive, like 270USD dealer
> only...   It's pretty easy to ck on any hub tho, just screw in the bolt sans
> wheel and ck for radial play (there should be virtually none).  Regular
> inspections and cleaning of wheel bolts is a good thing.  I actually had 1
> customer that ruined 2 hubs with 1 bad (slagged) bolt.
> SJ
> In a message dated 10/21/2002 1:34:54 PM Central Daylight Time,
> b.m.benz at writes:
> Jam nuts will keep the main nut from turning, but that is not the cause of
> the loss of clamping torque!  Also an impractical waste of time at the
> track, how would you get a second wrench on the main nut down in a typical
> wheel's bolt well?
> The studs and nuts or bolts are way understressed in this application, so no
> need to replace at any interval, IMO.
> Bernie
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