Lug Nut Torque - Got Search, now discussion - Subaru Forester Owners Forum
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post #1 of 31 (permalink) Old 03-30-2008, 04:41 PM Thread Starter
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Lug Nut Torque - Got Search, now discussion

I just rotated the tires on my 07 2.5x steel rims. I looked through the manual and no spec on lug nut torque. So I searched the forum and found multiple posts saying around 65 to 70 ft-lbs.

My question is, does this seem awful low to anyone. My old 91 Legacy used to spec 100 ft-lbs if I can remember back that far (college days). Over 200,000 miles on that ride, so i rotated the tires about 40 times. Every other car i have had has been 100 as well. My truck is spec'd to 150 ft-lbs! So I will continue to crank mine to 100 on the subie. what is the worst that could happen? Break a stud (replaced those before), or warp the rotors?

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post #2 of 31 (permalink) Old 03-30-2008, 05:59 PM
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I torque mine to 75 ft lbs. I've never had a problem.

I wouldn't recommend 100 ft lbs at all.

Michael

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post #3 of 31 (permalink) Old 03-30-2008, 06:14 PM
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Lug nut torque is in the owners manual but in a silly place to find it. Look where the flat tire changing instructions are. Or look on Scoobymods:

http://www.scoobymods.com/forums/showthread.php?t=2884

I use 70 ft/lbs myself. 100 is way too much, replacing a stud would be the least of your worries, both wheels flying off after snapping lugs in a turn now that is a concern. I've been witness to that on a WRX. FWIW the 07 Service manual says 73.8 Ft/lbs

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post #4 of 31 (permalink) Old 03-30-2008, 06:32 PM
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Torque spec is based on bolt diameter, thread pitch and material. 65-75 ft.lbs. is plenty. If you're paranoid, retorque them after a few miles. I think you'll find that they don't loosen...

'09 STI

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post #5 of 31 (permalink) Old 03-30-2008, 07:01 PM
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Quote:
Originally Posted by Peaty View Post
FWIW the 07 Service manual says 73.8 Ft/lbs
Mindless conversion from a round metric number I'm sure. Who has a torque wrench calibrated to a tenth of a foot-pound?

I use 68 because that's the year I got married. Some use 69 because it's easy to remember.

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post #6 of 31 (permalink) Old 03-30-2008, 07:09 PM
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As with the first post, my previous vehicle wheels were torqued to 100 ft.lbs. The Haynes manual for my son's 95 Neon Sport says 95 ft.lbs, 96 & later is 100 ft.lbs. I decided 100 ft.lbs was too much, so I use 80 ft.lbs for the Neon & MY03. This makes it easier, since I don't have to keep changing the setting on the torque wrench. BTW, this is the torque most tire dealers use.

The lug nuts on MY03 are M12X1.25, torgue range for this fastener is 70-80 ft.lbs.
My son's 95 Neon Sport are M12X1.5, torque range for this fastener is 70-80 ft.lbs. The factory recommends 90 ft.lbs.

I'm going to go against the group & say I put a small amount of NAPA 765-1382 Lock-Ease (Graphited Lock Fluid) on the wheel studs. The Lock-Ease "dries", leaving a rust preventing film, it's not oily. I have used this since I was a kid & I have never had any issues. In addition, I have never had to replace a wheel stud & no wheel has come off.

I always check my wheels after they've been driven on until there is no loose lug nuts. This will usually take two or more retorquings. The front wheels will be found to be loose more than the rear, due to the additional stress they are subject to. Most tire dealers will advise you to retorque after driving on newly installed wheels.

Once my wheels have stablized, they don't require torquing. I usually make an effort to check them at least once a month... just to be sure!

Bobby...

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post #7 of 31 (permalink) Old 03-31-2008, 08:17 AM Thread Starter
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After seeing how much force I had to do to get my truck to 150 ft-lbs specd, 65 to 70 ft-lbs still seems awful light. They are on my subie good and tight at 100 now, but next rotation i will back them off since nobody else has had their wheels fly off at 65 ft-lbs.
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post #8 of 31 (permalink) Old 03-31-2008, 08:21 AM Thread Starter
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btw, i had a friend in college with a toyota corrolla. She had a flat tire, after being into the dealer a few weeks before. The dealer must have way over-torqued the lugs, because I snapped the toyota tire iron, and the one from my subaru trying to get her lug nuts off (3 ft breaker bar, i am not that strong). Ended up having to use a portable impact wrench to get the lugs off.
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post #9 of 31 (permalink) Old 03-31-2008, 08:36 AM
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***? Is there some kind of urban myth going around about wheels falling off?

Why anyone would over stress lugs beyond their design capabilities is beyond me.

Think about it- you're over tightening your lugs thinking it's safer when in reality you're creating an unsafe condition by over stretching the threads...

'09 STI
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post #10 of 31 (permalink) Old 03-31-2008, 08:36 AM
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If you torque your lugs on to tight you can actually deflect the shape of your rotor, causing it to feel like it is warped and making for uneven wear.


05 Forester XTi Premium M/T (bobbytuned VF39)(his)
05 Forester X A/T (hers)

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post #11 of 31 (permalink) Old 03-31-2008, 08:42 AM
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Quote:
Originally Posted by shamrockshooter View Post
After seeing how much force I had to do to get my truck to 150 ft-lbs specd, 65 to 70 ft-lbs still seems awful light. They are on my subie good and tight at 100 now, but next rotation i will back them off since nobody else has had their wheels fly off at 65 ft-lbs.
If you recheck the torque & they're not loose, the 65 to 70 ft.lbs. should be fine. I think the trick is to make sure they stabilize at whatever torque you decide to use.

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]

'07 FSXT - COBB Surgeline dyno stock Protune - Stage 1+
'03 X +AVO turbo kit = XT (son's)
'95 Neon Sport

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post #12 of 31 (permalink) Old 03-31-2008, 09:15 AM
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Usually torque specs are for dry un-lubed threads unless otherwise stated in the spec. I'd be leary of putting anything on them.

cut and paste from my link:

Quote:
Here's why: Bolts or studs provide clamping force by being purposely stretched. Most torque specs bring a bolt well within its elastic limit. Then when loosened they will return to their original length and can be safely reused (Some bolts, including many head bolts, are purposely stretched past their elastic limit, and can not be reused). The torque wrench is the most convenient-but not the most accurate-method of properly stretching automotive bolts. Engineers spend hours correlating the proper bolt stretch to the required turning effort. About 90% of a torque specification is used to overcome friction; only 10% of the specified twisting effort provides clamping force.

It is no surprise then that most lubricant tables recommend a 40-45% reduction of applied torque when using anti-seize on a bolt. So, a lug nut coated with anti-seize should be tightened to a maximum of 49 ft-lbs. Tightening this lug nut to 85 ft-lbs. means it is now over-torqued by 73%! Considering that most torque specs stretch a bolt to within 70% of its elastic limit, over-truing by 73% will easily send the bolt or stud well beyond its elastic limit-and could be dangerously close to its failure point.

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post #13 of 31 (permalink) Old 03-31-2008, 09:27 AM Thread Starter
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If subaru was concerned about lug nuts being over or under torqued, perhaps they should put the design torque Ft-lbs in the specifications section of the owners manual, not burried someplace on how to change a spare tire.
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post #14 of 31 (permalink) Old 03-31-2008, 09:40 AM
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Google search much? Took me about 2 seconds to find this...http://www.tirerack.com/wheels/tech/...jsp?techid=107

'09 STI
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post #15 of 31 (permalink) Old 03-31-2008, 09:53 AM
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Quote:
Originally Posted by shamrockshooter View Post
If subaru was concerned about lug nuts being over or under torqued, perhaps they should put the design torque Ft-lbs in the specifications section of the owners manual, not burried someplace on how to change a spare tire.

Well most people will only replace a wheel when they get a flat if forced to. Many do not even have a torque wrench. I suppose that's why they put it in that section. Below is the section from my 04 owners manual from the flat changing section.

Even in this section is says not to lube the threads.
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