Oppo PSA - Remember to check your lug nuts

"You can tell a Finn but you can't tell him much" (youcantellafinn)
11/06/2014 at 16:04 • Filed to: oppo psa

Just a reminder to check your lug nuts for proper torque 50-100 miles after reinstalling your wheels. Since it is time to activate winter mode for large chunks of the country a lot of us have been / will be putting on winter tires, so remember to check the torques. Have a rally car on above Brockway Mountain Drive courtesy of !!!error: Indecipherable SUB-paragraph formatting!!! .

If you need more incentive to check your lug nugs, I checked mine on the Subaru after ~175 miles and they all needed a couple degrees to get back to proper torque. I did have an awesome drive last Thursday before retorquing them. I had a family engagement in the morning and then blew off the rest of the day to go for a 130 mile loop to clear my head. Well worth it as I was grinning like an idiot while blasting through the twisties in the STI and work has been a little easier to deal with since then.

DISCUSSION (17)

MonkeePuzzle > You can tell a Finn but you can't tell him much
11/06/2014 at 16:36

Kinja'd!!!

this is the wrong bumper...

You can tell a Finn but you can't tell him much > MonkeePuzzle
11/06/2014 at 16:43

Ummm.... because rally car?

MonkeePuzzle > You can tell a Finn but you can't tell him much
11/06/2014 at 16:45

but the V4 WRX bumper is so much sexier than the one they have on there

Decay buys too many beaters > You can tell a Finn but you can't tell him much
11/06/2014 at 16:47

Also, if changing wheels frequently, anti seize is your friend. Especially true for winter climates.

Klaus Schmoll > You can tell a Finn but you can't tell him much
11/06/2014 at 16:52

Do you know the proper torque in metric? I have a torque wrench that has been sitting in my trunk for quite a while now.

You can tell a Finn but you can't tell him much > Klaus Schmoll
11/06/2014 at 17:25

The required torque depends on the car. My STI is 65 ft-lbs, my wife's Escape is 100 ft-lbs. if you don't have the manual you should be able to find it online. For reference 1 ft-lb equals 1.356 N-m.

You can tell a Finn but you can't tell him much > Decay buys too many beaters
11/06/2014 at 17:26

Definitely, I put it between the hub and the wheel. None on the studs though, that is bad. Torques are based on dry threads.

You can tell a Finn but you can't tell him much > MonkeePuzzle
11/06/2014 at 17:27

Probably needed more air to the huge FMIC.

BaseTrim > You can tell a Finn but you can't tell him much
11/06/2014 at 17:41

Came for the pic. Thanks!

Decay buys too many beaters > You can tell a Finn but you can't tell him much
11/06/2014 at 17:48

I always put it on the studs, factory torque is based on fresh fasteners which usually include an anti seize. I have 2 years of heavy track usage with about 20 wheel changes/year to back me up.

It's the lug seats you want to avoid lubricating at all costs.

Klaus Schmoll > You can tell a Finn but you can't tell him much
11/06/2014 at 17:50

Good to know the ratio! Thanks.

thebigbossyboss > You can tell a Finn but you can't tell him much
11/07/2014 at 08:22

65 ft lbs? That's it?!?!

Do your wheels come off on a regular basis?

You can tell a Finn but you can't tell him much > thebigbossyboss
11/07/2014 at 09:02

They come off every spring and fall to swap between winter and summer tires. It surprises everyone that they use such a low torque, but that is what the manual calls for so that is what I torque them to.

thebigbossyboss > You can tell a Finn but you can't tell him much
11/07/2014 at 09:03

I meant fall off. But yeah, I dunno if that's what the manual says I guess. I am just surprised. Mine is about 90 ft lbs.

You can tell a Finn but you can't tell him much > Decay buys too many beaters
11/07/2014 at 09:36

I've never seen studs come with anti seize and putting anti seize on the threads can result in the clamping force being so high it causes the stud to fail. Read your manual, if it specifically states that the studs are to be coated with anti seize then do that. If there is no mention of anti seize then it is assumed that the studs are clean and dry when being torqued.

Clamping force for a fastener can be found by F=T/Kd where F is force, T is torque, K is a constant and d is the bolt diameter. I did some quick back of the envelope calculations based on my wifes Escape. Calling it a 1/2" fastener torqued to 100 ft-lbs and I figured it for clean threads (K=20) and anti seized threads (K=12). Clean threads result in a clamping force of 12,000 lbs which gives a stud stress of 60,000 psi. Anti seize increases the clamping force to 20,000 lbs giving a stud stress of 100,000 psi. The yield strength of a grade 8 fastener is 130,000 psi. This gives a factor of safety of 2.17 for clean threads and 1.3 for anti seize coated threads. In engineering terms anything with a factor of safety of less than 2 is generally considered unsafe. Stud stress was figured by s=F/A. Bolt strengths and the clamping force equation are from Mechanical Engineering Design Fifth Edition by Schigley and Mischke.

TL;DR Adding anti seize to bolted connections that don't specify it can cause them to fail.

You can tell a Finn but you can't tell him much > thebigbossyboss
11/07/2014 at 09:41

They haven't fallen off yet.

Decay buys too many beaters > You can tell a Finn but you can't tell him much
11/07/2014 at 16:43

First off your K is off by 2 decimal places.

Second, a k=0.20 is for a NEW/CLEAN fastener, you will never see that in practice unless you replace studs and sonic clean lugs each time you re-install. Anti-seize counteracts corrosion and pitting in used fasteners and returns the k value into the like new realm. I've sheared off half a dozen studs/bolts before I started using anti seize, since then I have not had a single issue. (for reference the permatex I use claims a friction coefficient of 0.13 which should lead to a KA in the 0.18 range)

Kinja'd!!!

Third, god I wish I had a proper strain gauge so I wouldn't have to faff about with theoretical K values that I have no way of confirming in my particular application.