Snapped wheel studs, bad technique to blame?

[sciphi]

Originally Posted By: Rand
so when are you replacing the other 10 studs?

if half were that bad I think I'd want all new quality ones.


That might be another weekend project. Not soon, as I'm not anxious to work on the car anytime soon.

 

[mechtech2]

Another possibility is that they were previously over tightened.
The damage did not show up until now.
100 lbs is a lot for a passenger car.

 

[Stu_Rock]

Originally Posted By: mechtech2
100 lbs is a lot for a passenger car.
That's the standard spec for GM cars.

 

[javacontour]

All GM cars? That's the first thing I was thinking too, that 100 ft*lbs was pretty high. I think I go 80-85 ft*lbs on all my cars, IIRC.

What size fastener and what is the typical torque range for that type fastener?

 

[The_Jeff]

Probably a 12mm, 1mm pitch.

 

[Kestas]

Originally Posted By: mechtech2
100 lbs is a lot for a passenger car.
The torque specs for wheel studs among all my vehicles range from 65 to 105 ft-lbs. The highest is on my Mercury Grand Marquis.

 

[yonyon]

Originally Posted By: javacontour
All GM cars? That's the first thing I was thinking too, that 100 ft*lbs was pretty high. I think I go 80-85 ft*lbs on all my cars, IIRC.

What size fastener and what is the typical torque range for that type fastener?


Not all GM cars, no, just most. Some specify higher torque and others are rebranded cars from an asian make and have a fine thread pitch. In GM-land you can pretty much assume that if a lug torque higher than 100 is called for, it will require a 22mm or larger socket.

 

[JC1]

Originally Posted By: sciphi
I recently had to replace two snapped wheel studs on my Cruze ... torquing the lug nuts down to the recommended 100 ft/lbs of torque with my torque wrench.


100 ft lbs seems excessive. Did your cruze come with a corvette motor? LOL My cars have the recommended torque at 75 ft lbs.

I guess the extra 25 lbs is for the screws to get through the GM executives thick skulls back at head office in Michigan!

 

[George Bynum]

We have a Chevrolet Venture, Chevrolet HHR, and Ford Fusion. All 12mmx1.5mm and specify 100 lb-ft. I did a little web searching, and found http://www.gorilla-auto.com/pdf/GAG10.pdf which suggests that 12mm lugs for cars and light trucks "MAY" be 75-85 lb-ft lacking a manufacturer specification. Quick research on real high strength fasteners (grade 12.9) show about 120 lb-ft recommended, with grade 10.9 at about 60 lb-ft.

The manufacturers must use some pretty good stuff ...

Other than manufacturer specifications, I'd agree it seems high for what I'd expect to be approximately SAE Grade 5 ... so they must be closer to SAE Grade 8.

I've not run the numbers, but it would be my GUESSTIMATE that 100 lb-ft on that pitch would result in about 120,000 psi stress.

 

[sciphi]

I was going by what the owner's manual stated. My other GM cars have used the same torque rating without issue.

No mention of grade on the OEM studs. The Dorman studs that replaced those had a 10.9 cast into them.

By some of the charts I see, 80 ft/lbs is the most a grade 10.9 fastener should take. I'll tighten my wheels to that spec, and call it good.

BTW, the Dorman studs that went on were made in the USA. Or at least the box was!

 

[charbaby]

I keep all of our aluminum/steel wheels at 80 ft.lbs.

Lexus-76 ft/lb
Mazda-86 ft/lb
Nissan-72-87 ft/lb

 

[CapriRacer]

Originally Posted By: sciphi
I was going by what the owner's manual stated. My other GM cars have used the same torque rating without issue.

No mention of grade on the OEM studs. The Dorman studs that replaced those had a 10.9 cast into them.

By some of the charts I see, 80 ft/lbs is the most a grade 10.9 fastener should take. I'll tighten my wheels to that spec, and call it good.

BTW, the Dorman studs that went on were made in the USA. Or at least the box was!


Just to clear up a misconception:

The 10.9 is the metric way of indicating the breaking strength of the bolt - ala the SAE grades. 10.9 is equivalent to Grade 8.

But the breaking strength (and therefore max torque) is not only a function of the grade of the bolt, but also it's size!!!

So a larger bolt would have a higher max torque.

 

[sciphi]

Thanks, Capri!

 

[George Bynum]

Originally Posted By: CapriRacer

Just to clear up a misconception:

But the breaking strength (and therefore max torque) is not only a function of the grade of the bolt, but also it's size!!!
I know that Capri knows this, and likely left it out for simplicity, but I like to confuse the issue ... clarity by obfuscation ... or something like that ...

Tension to torque relationship depends on the thread pitch as well ... hence my hedge since the real data I had on 12mm had 1.75mm pitch, not 1.5mm as used on cars. The finer pitch loads a little more (think flatter slope) but has more stressed area (think shallower threads). AND ... we've talked lubrication of studs too ... more tension for less torque ... SNAP!

The only RIGHT way is too difficult to do in the field ... measure stretch. Torque is better than nothing.

 

[Kestas]

All the studs I've seen are either Grade 8 or 10.9, with the exception of one stud application that was an "enhanced" 10.9.

 

[SwampSurvivor]

I go until I can feel the lugnut is tight. Never had a wheel come off or snapped a stud that way.

The one time I used a torque wrench, the wheel came lose.

 

[Falken]

I agree with what Miller88 is saying.

If the torque wrench is 24" and not calibrated, and clicks too soon, you may walk away saying, "well, that is a lot of leverage, I used a toque wrench, all good".

Then your wheel falls off.

I just changed over my girlfriend's Winter tires yesterday (she only does 1-2km a WEEK. The car is 2 years old and she ONLY has 4000 KMs on it!!!!). So Fall is really setting in here (very cool out), and I figured I'd get her car out of the way, and she'd be ready if there is some freezing rain etc.

Well, she lives in NDG down a one way street, so I loaded up the car with my toolbox and her 4 Winter tires (16" Goodyear Nordics, with a traction-control equipped car, a very decent performing cheap tire).

So I brought her 2010 Mazda 3 hatch down to a bowling alley parking lot (out of the way) and I changed over her tires.

When I put on a tire, I snug them with a 1/2 inch drive 8-10" long breaker bar. You can use a 1/2 inch drive ratchet with the shortest handle you have, around 8".

When I cracked all the nuts loose, I used a 24" ratcheting breaker bar, and man, they were hard to get loose so they must have been around 300 ft-lbs or more. The last time she had it done at the dealer with an oil change, so they must have put them back with a gun. (Wasn't happy to find this).

A curious thing I noticed: the lugs and center hub had motor oil on them. That's right, poor man's anti-seize done by the good old dealer, who charges 40$ to change over your tires that are already on rims. So I had a tough time breaking these nuts loose, and they were LUBED. That is some massive effective torque on those lugs!!

Lug nuts should NEVER be lubed, it throws off the torque spec and over stretches the studs. Also, who wants nuts spinning loose?

So, when I was done, as a test for this forum, before using the torque wrench, I snugged them all "reasonably tight" with my 24" ratcheting breaker bar.

Then I set my torque wrench to 90ft-lbs, and started torquing the wheels. Each nut didn't budge and the torque wrench clicked. This means the lug nuts were over torqued. I backed them all off and torqued them all properly.

My message here is be very very gentle with a 2-foot long anything when it comes to passenger car lug nuts.

Hand start the nuts, snug with an 8-10" long breaker bar or 1/2" drive ratchet, lower the car, and use a torque wrench that goes up to MAXIMUM 150 ft-lbs (these are shorter than torque wrenches that go up to 250 ft-lbs so less leverage).

If you plan on doing A LOT of family's/friends tire change overs, invest in a beam-style torque wrench, I'm sold on this idea. So you just snug 10 ft-lbs shy of the spec with the beam, then click to spec with the clicker torque wrench.

 

[SwampSurvivor]

I had some tires balanced while on the car at WalMart once.

When I went to change them, I had to use a 3 foot breaker bar on ALL of the lug nuts.

How tightwere they?

 

[Falken]

Wow Miller88, an impact if held on the stud when it starts to really labor and bang the stud on tight would generally be around 500-600 ft-lbs.

Then a little corrosion sets in, adding another 50 or so ft-lbs loosening resistance, and no, you probably wouldn't have been able to remove your tire if you were stuck at the side of the road with a flat and the factory lug wrench.

Maybe I'll leave my flex head 24" breaker bar under my front seat. Could be very useful for any road hazards you may encounter as well...

 

[4x4chevydude]

I think i would say the studs were bad your technique sounds fine and I know alot of times Ive blasted on lugs and then torques them and it just clicked right away and my studs were fine....must have been weak