[s-cars] More on audi wheel bolts/studs/torque

[wolff at turboquattro.com]

That is the specified dry procedure for subframe bolts. Torque to 25 ft-lbs,
plus 1/4 turn....
Wolff
"Nobody can forget the sound." - Michele Mouton

----- Original Message -----
From: "Randy McCall" <redrandy at pacbell.net>
To: <200q20v at audifans.com>
Sent: Tuesday, October 22, 2002 11:03 PM
Subject: Re: [s-cars] More on audi wheel bolts/studs/torque


> Awright, Wolff throws in an equation for wet vs. dry torque!
>
> So please allow me to throw my two relatively uneducated pennies into the
> pond - torque is easy to get right, but correct bolt tension (thats the
real
> deal we're lookin' for!) for a given torque is a highly iffy thing with
> contaminated or dirty threads, poor condition, corrosion, etc.  When I
long
> ago did high strength 7/8" galvanized (extrememly poor wrt clean threads)
> windmill hardware we torgued to a low starting load (enough to pull the
> joint together and take up slop) and then did turn of nut method.  Doesn't
> matter whether its wet or dry, the same tension in the fastener is always
> generated that way as the thread pitch (angle of the ramp if you will)
> determines the amount of elastic stretch in the fastener per turn of the
> nut. I'm not as up to speed on all of the metalurgy being bandied about,
but
> unless I forgot my basic engineering, for a bolt type fastener you want to
> get up the stress/strain curve a bit, within the elastic limits of course,
> and stand pat.  Torque is just an easy way to get to that point if you
have
> lots and lots of faith in correlations.
>
> The caveat to that is of course the crux of the other half of this ongoing
> debate, creep of the wheel allow around the bolt head interface, degree of
> planar contact between hub and wheel and whatever other goodies you've
> placed between the two(do they really touch each other, or does the bolt
> preload get used drawing the two together...?), and other minutia that
> probably assume a level huge importance if ignored!
>
> So why not apply a good dose of A/S, torque to low level (for beginning
> tension point) and then head on to the turn of nut method?  Yer crusty
> studs/bolts will be at the correct tension regardless of the goop used,
and
> at least they come off when you want to swap those salt encrusted winter
> tires for summer meat.
>
> Randy
> '91 20V 200TQW