Safety Tech Tips - Wheel Torque

[Jimbeau]

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[size=3]Just a few tips borrowed from Bill Neal of 10/10ths Motorsports March news letter.

Wheel Torque

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[suP][suB][size=4]"Proper installation requires that the wheel lug torque be set to the recommended specification for your vehicle. These torque specifications can be found in your vehicle's owner's manual, shop repair manual or obtained from your vehicle dealer.  (also conveniently located on the door jamb of most cars )[/suB][/suP]

[suP][suB]Unless specifically stated otherwise, wheel lug torque specifications are for clean and dry threads (no lubricant) that are free of dirt, grit, etc. [/suB][/suP][/size][/size][suP][suB]Applying oil, grease or anti-seize lubricants to the threads will result in inaccurate torque values that over tighten the wheels.  (I've seen this around the paddock so suspend your disbelief already)[/suB][/suP]

[suP][suB]A thread chaser or tap should be used to remove any burrs or obstructions of the threads allowing the lug hardware to be turned by hand until it meets the wheel's lug seat. Once lugs are snugged down, finish tightening them with an accurate torque wrench.  (Wally says my $9 Harbor Freight wrench is junk, but I checked it and it is accurate)[/suB][/suP]

[suP][suB]Use the a crisscross sequence for the number of wheel lugs on your vehicle until all have reached their proper torque value. Be careful because if you over-torque a wheel, you can strip a lug nut or hub, stretch or break a stud or bolt, and cause the wheel, brake rotor and/or brake drum to distort. (if you happen to have a 4-lug wheel the sequence is top, bottom, left, right) [/suB][/suP]

[suP][suB]Use the dry wheel lug torque values specified in the vehicle's owner's manual, shop manual or obtained from the vehicle dealer/service provider.[/suB][/suP]

[suP][suB]Don’t forget to give your wheels a very good inspection before and after each event. There have been reported cases of total wheel failures at other events. A good inspection can minimize this. "[/suB][/suP]

[suB][suP]This seems like such a simple thing, yet we've all probably witnessed if not experienced at least one example of what can happen if this simple task is taken too lightly. (no names please) :dude:  For me, I learned first hand when the improperly torqued wheel (by me of course) on my dad's '71 Ford LTD  began to wobble at highway speed eventually destroying the wheel.  Of course my dad made me buy a brand new one even though I could have gotten one at the junk yard for less than half.   Education is always expensive but imagine if this had been at the track.....[/suP][/suB]

[suB][suP]I seem to be spending a lot of time imagining things at the track these days.....[/suP][/suB]

[betegh9]

Jim,

Thanks for the update.  I have seen that even though dry torquing the studs is proper, many guys have had trouble removing studs after a heavy breaking session on the track due to the nut seizing from the heat generated.  I have been using a good ANTI-SIEZE  compound (just a drop) on each stud when they seem dry..\  Because of the lubricating properties of the paste, I add 2 footpounds of torque to the lugs over spec at all my wheels, and cross my fingers, I have had no problems whatsoever.

[Jimbeau]

Nick,

I hear what you're saying but what if the anti-seize compound reduces the friction coefficient to the point where an additional 10 pounds is needed?  What if it's 20?  It's probably not, but the point is you don't know and crossing your fingers is probably OK for normal driving, but what we're doing isn't normal and it's not just your safety that we're concerned about.  This is a situation where the risk probably doesn't out-weigh the questionable benefit.

I torque my lugs at 100lbs and have never had a problem breaking them loose even when hot.  I would suggest a 1/2 inch breaker bar and a little patience over anti-sieze compound.  DeWalt, Craftsman and others also have affordable 18v 1/2" cordless impact drivers that make easy work of removing lug nuts. 

I just got the DeWalt as a 25th Anniversary present.  "25 years is the "DeWalt Anniversary" guys in case you didn't know."

Jim

[Guest]

betegh9 wrote:

Jim,

...I have been using a good ANTI-SIEZE compound (just a drop) on each stud when they seem dry.. Because of the lubricating properties of the paste, I add 2 footpounds of torque to the lugs over spec at all my wheels, and cross my fingers, I have had no problems whatsoever.

If you have added a lubricant to the wheel studs, you should lower the torque setting on the wrench. Otherwise you will over tighten the nut & studs. For most other fasteners on the car, the torque spec is assuming a lubricated thread.

[KennyB]

Oh Great.  Just what we need...another controversy with safety implications.  Seriously, though, I'm glad you brought this up.  I have always used a little anti-seize on the lugs since this was recommended in the owner's manual of my '89 930.  I've been more concerned about damaging a frozen lug nut/bolt than about improper torque setting.  I'm now in the habit of checking torque before each session.

I've been thinking about going back to studs/nuts and I suppose the same issues would apply, but I would hate to dislodge a stud trying to remove a frozen on lugnut.

[cjbcpa]

I don't think a stud could get dislodged. They're not threaded in like exhaust manifold studs (at least on my car). If my experience is typical, they are inserted into the hub from the rear and are indexed with splines to match up with straight grooves in the hub (there is a flange on the rear of the stud that acts as a stop. As you tighten the lug nut, it actually draws the stud tighter into the hub. As a result, over tightening can cause the stud to stretch, weakening it. If they were threaded in, I imagine we would all be familiar with stories of people backing their studs out, but I've never heard one.

This is a picture of what I'm describing:

[img]file:///C:/DOCUME%7E1/Chris/LOCALS%7E1/Temp/moz-screenshot.png[/img]

[emayer]

Great topic guys.

I'm sitting here trying to figure out how to get through Tech with center-locks!

Great concept but a real PITA....

[cjbcpa]

Funny,

I was garaged near a guy at T-bolt last October who had centerlocks his Porsche.

He asked for my help putting his wheels on. Not sure how much of this was drama for my benefit, but it was some absurd multi-step process putting those on. In the end, he had this humongous torque wrench with an extended breaker bar on it that was necessary to get the torque up high enough to the factory setting.

Maybe Porsche has made a secret pact with folks like Doughtery's to make it almost mandatory to hire track-side service.

 

CB

[JoeP]

I worked for a couple years in a refinery with all sorts of fancy machinery, pumps, and compressors.  We were told exactly the opposite - use copper-based anti-seize on every screw and bolt on which we did not use LocTite.  They said that torque settings on dry bolts would not be accurate. 

They said that a bolt or nut does not move until you apply a fixed threshold of extra torque.  That is,if  a nut is already at 90 FtLb, it will not move when you apply 91 FtLb.  It will only move with, say, 97 FtLb.

We were told that the torque threshold to get dry nuts & bolts moving was much higher than when antisieze was used.  Therefore, going from 90 to 95 FtLb was difficult.  The nut might not move until 105.

Anyway, that's what I was told -- in a very loud voice by a big guy with a wrench in his hand. 

[betegh9]

emayer wrote:

Great topic guys.

I'm sitting here trying to figure out how to get through Tech with center-locks!

Great concept but a real PITA....

Eric, I'll help you with the wrenching (it is a 2 man job) if I can be your tire warmerhock: