Re More on Wheel Torque
b.m.benz at prodigy.net
Thu Oct 24 07:36:32 EDT 2002
Good, informative posts, you guys!
IMO, "thread stretching", exceeding the yield point of Audi bolts, should be
of no concern at these torque levels, nor even if they were made of low
carbon cold rolled steel. Lots of safety factor built in here.
What is the frequency of aluminum wheel hole or bolt circle cracking, in
your experience? IMO, it would have little corrolation to overtorquing,
excessive clamping force, and more to do with poor cast materials, and
clamping forces lower than cornering forces.
> From: QSHIPQ at aol.com
> Date: Thu, 24 Oct 2002 08:35:54 EDT
> 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: Re More on Wheel Torque
> [ Picked text/plain from multipart/alternative ]
> Looking at it a bit differently, Wolff. If you use A/S on a audi wheel bolt,
> and torque to 81 ft/lbs, you have the equivelent of torquing a dry bolt
> install to 110 ft/lbs. Kinda puts those A/S use claims in perspective. In
> reality, with A/S and audi dry spec all you are claiming is that you are
> routinely way overtorquing your wheels. Make sure you routinely ck the
> hardware for wear, thread stretching and wheel hole cracking.
> WRT porsche Jolly, a couple things to consider with that claim (I'll assume
> it's valid). First, *if* it is specified to use lubricant, then they are
> giving you a wet torque specification. With an alloy nut (especially), if
> you use the wet torque specification on a dry nut, you are *undertorquing*
> the wheel by definition. Using anything other than the exact specified
> lubricant will over/undertorque that application.
> I'm intrigued by a few things researching this intensively. I've seen a
> bunch of TSB's regarding "not" using lubricant on bolts/nuts/studs. One of
> the truck fleet procedures didn't say anything about lubricant, it only
> listed "140lb/ft (dry)". Wonder if that's enough? Audi and other marques
> just assume you know what that means. Unless specified otherwise, ALL
> torques should be considered as dry torque values.
> 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.
> Scott Justusson
> In a message dated 10/22/02 11:38:01 AM Central Daylight Time,
> wolff at turboquattro.com writes:
> The first reference (DANotes) and the third reference (loctite) basically
> agree that the K number of a lubed thread is between .11 and .18 depending
> on the lubricant. The first reference lists .30 as the K number for an "as
> received, stainless on mild or alloy" thread and .20 as the K number for an
> "as received mild or alloy on same" thread . Loctite says:
> T=torque (in-lb, ft-lb, N-m)
> K=torque coeficient or nut factor (determined experimentally for their chart
> of lubes and specifically not "friction coefficient" which is a different
> lower value)
> F=clamp load (lb,N)
> D=nominal diameter of bolt (in, ft, m)
> So if we keep F and D constant while changing K (the type of lube or lack of
> lube and thread material), T will vary by as much as 63%.
> That's seems like a lot to me. If we use the lower .20 dry thread number and
> take an AS K number of .15 which looks like about an average value in
> loctite's chart then either F goes up 25% or you have to cut the torque 25%
> to not raise your clamp load. What this tells me is that you can't just lube
> your lug bolts and torque them up to 82 ft-lbs or you are exceding the
> factory expected clamp load. Also, anytime torque is given for any threaded
> fastener, it is critical to note what (or if any) thread lube is specified.
> Will I lube and torque my lug bolts to 61 ft-lbs? Absolutely not and neither
> should you based on my uneducated ramblings and an unknown real K number for
> Audi size and grade lug bolts. Locktite says "In critical applications it is
> necessary to determine K values independently."
> Throwing more chaff out for the radar,
> "Nobody can forget the sound." - Michele Mouton
> 200q20v mailing list
> 200q20v at audifans.com
More information about the 200q20v