Torque settings on lug nuts?

[Wil Ferch]

Guys:
As usual , the original thread feeds a number of peripheral issues

Couple of things...I wouldn't worry much about the 94-96 ft-lbs discrepency..it just doesn't matter. In fact, the whole torque number routine is not optimal...as the deciding factor is to "close-in" on clamping force, and torque settings are the nearest-good ( bad?) approximation of getting to that clamping force target ....note all the variables like lubed / dry ( itself the cause for 30-40% changes in target torque values)....that come into play.

Ok ...let's talk torque wrenches. A good idea is to have a click type ( easier to use and it ratchets)...backed-up by a cheap ( but almost always accurate) beam type, just as a quick calibration. The beam types don't lose their accuracy, unless mishandled, whereas the click type can get out of calibration...and very badly out of calibration, too.

--- Wil Ferch

[Dana_Drury]

Why do click types go out of calibration?

[JEB]

People are going to start making jokes about how many Pelicanites it take to change a tire.

Jeb
'79 930

[Wil Ferch]

Hi:

It's almost like asking why sh#t happens...it just does.
Apparantly , things like internal spring tension ( and changes with time and wear) and small ball detents that are part of the internal workings...all conspire to make them lose calibration. Some manufacturers require you to "unload" the spring tension after every use, and not store it in its tensioned condition.

It is very common in industry to have these periodically re-calibrated, with a certified date / calibration sticker attached...to make sure all is still OK. The beam type, OTOH...is simply a long steel "beam" that bends and returns to position..and unless it was dropped and the initial setting is no longer "zero"...it is usually very accurate throughout its service life. It would work as a very cheap tool ( usu. $30 or so)... to "check" your click type...IMHO.

-- Wil Ferch

[JWest]

The ultimate torque wrench!
http://www.sheldonbrown.com/tork-grip.html

[pwd72s]

James, LOL here! Thanks!

[KTL]

I can see the argument that the torque spec is a dry one, since there's no mention of the use of lubricant with the torque value. But, I gotta think anti-seize is a must. The sound that those aluminum lug nuts make when they're dry against the lug seat is just plain sickening.

I think i'm sticking with the use of anti-seize. Those who disagree should consider the consequences of a seized/stripped lug nut on your precious Fuchs wheels. It's not a pretty sight and not easy to get the sheared lug out. The end result is a damaged wheel and a damaged wheel stud since your only alternative for removal is the dreaded hammer and chisel method.

[steve911]

OK
we've settled on 94-96 as the torqued-spec.
dry vs wet is still open
click-type vs beam torque wrenches have been discussed

but no one has mentioned the lug nut socket with nylon inside so as not to ding up the aluminum lug nuts??

shocked, I'm simply shocked!

[Dana_Drury]

Originally posted by Wil Ferch


It's almost like asking why sh#t happens...it just does.

No, no, no... Its not like "*****" happens. There is a specific mechanic reason as to why the click types go out of calibration as opposed to the beam types... "***** happens" because Murphy is out having fun.

As for nylon inserts in sockets, use a zip lock bag, works just as well. Place it over the nut, then place your - torque wrench or lug nut socket over the offending nut, viola! you have protected it...

[Britwrench]

I was always under the impression, both from factory manuals and at Porsche training courses that Optimoly anti-seize should be used on the threads and cones of the wheel lugs. The torque is 130Nm and all wheels of 17" and bigger should only be tightened with the wheels off the ground.

[Langers]

Ok to stop you guys all arguing I went to the local Porsche mechanic this afternoon and it is..... 130Nm w/anti-sieze.

[Early_S_Man]

Actually, the torque specified in the factory service manual is 13.0 mkp AND 94 lb-ft ... the 130 Nm is a 'rounded up' translation using a conversion factor of 10, instead of the correct 9.81, so there is your 2% error and 96 lb-ft rating used in some places in Bentley! That Bentley also lists 94 lb-ft is other places is a bit confusing! The spec books note the discrepancy from using the incorrect conversion factor, and basically say that the 2 % error is 'good enough!'

[warment]

The torque setting for the wheels on my 2000 Mustang GT is 80 lb/ft. Not a Porsche, but anyways...

[Early_S_Man]

Bill,

Not 14 mm, either! Are they still 1/2", or did Ford downgrade to 12 mm the way GM did?

[skinnerd]

I've been autocrossing/tracking it for years (read many, many mount/dismounts of the tires), and I've always stuck with ~95 ft/lbs agreeing with most people here. Every so often, I'll put a little lubricant on the threads as well. Have never had a problem.

It's imperative to unwind a click type torque wrench after every use. Keeping the wrench set at ~95 ft/lbs will overtime radically change the properties of the spring and your torque readings. Sears makes a great, economical torque wrench. They also have a recalibration service that doesn't too awfully long.

[dad911]

Ok, I'll bite. Britwrench, why do you torque 17" & larger wheels off the ground? & how do you keep them from spinning?

[Britwrench]

Porsche said that the 17" and larger wheels would not be
hub-centric if the wheels were tightened with the weight on the wheels.
Apparently, although I have never heard of it, that the nuts can come loose if tightened with the wheels on the ground.
The rears are easy to tighten, just apply the park brake. As for the fronts, either get someone to help or hold the wheel with your hand. Finally check with the car on the ground.

[HarryD]

I checked with my locally respected p-car expert. He suggested a very light amonut on the shoulders but none on the threads. To me this makes the most sense as the concern (to me) is fusing the bolts to the alloy wheels.

[TimT]

and basically say that the 2 % error is 'good enough!'

OK ill just chime in and add a thought or two..

If you look in AASHTO, AISC, AWS and Im sure other acronymed manuals, You calibrate a torque wrench in a tension measuring device. The tensile strength of the bolt material is a known value, and the bolt recommended to be used for calibration is "lightly oiled".

Im sure all the auto manufacturers have standards they are required to follow that allow there product to be used on public roads. The SAE, TUV and propriatery specs would not call for dry threads... a lubricant of some sort is alway present to prevent galling of the mating surfaces

On lug nuts the application of anti-sieze should be conservative at best, this is an application where more isnt better.

BTW torque values for the bolts that hold together alot of the bridges we drive over?

7/8 bolt.... 600ft/lb to 900ft/lb torque

Porsche said that the 17" and larger wheels would not be hubcentric if the wheels were tightened on the ground

Ive seen lots of peeps do this, they rotate the wheels and snug up the nuts, then partially lower the car and final torque the bolts.

[Scott Chytil]

From the '84-'89 factory manuals:

Page: 44-6

Removing and Installing Wheels on Car

1. Use special tool P 300 in perfect condition. (everyone has one, right?)... Never use impact tools.

2) Lubricate threads and nut contact base with Optimoly TA.

3) Always tighten nuts to specified torque of 130 Nm (94 ftlb).

I could not find a similar reference to Optimoly in the earlier manuals. All torque specs were for 94 ft/lbs though.

Scott