Why did this wheel stud break? Metallurgy issue?

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Today, I was doing a routine tire rotation on the ol' 2012 Honda CRV, and was doing the final tightening of the lug nuts. The RF wheel was the last step. Cris-cross sequence on the 5 lug nuts, all tightened nicely but one stud would not bottom down. Tried to back off but the stud was snapped off.

Power tools have never been used on the car since I bought it new, and I'm the only person who did the tire rotations over the years. Always did manual tightening. Granted, I don't have a torque wrench, but I'm 150 lbs and apply this weight on the 9-inch long Honda tire iron, which equals 112 ft-lbs. I use a little grease on the studs, so maybe this amplifies the torque by 15% and makes it 128 ft-lbs. This is over the spec'ed 80 ft-lbs by Honda, but surely it is not enough to snap the stud. We've all read of cases on BITOG where 200 ft-lbs or more were applied and the studs were none the worse for it, right?

Looking at the damaged area, I see near the center some metallic grain that is perpendicular to the circumference of the stud. Any comments, guys? Metallurgy issue?
 

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308
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It's steel, so it was stressed over time from torqueing beyond the intended 80 ft/lbs.
Honda is known for using just the right metallurgy in just the right places & amounts on their products.
Looks like you found the limit.
 
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Arizona
Remember that unless you use an X lug wrench that the applied tightening torque is not balanced axially but instead side loads the stud which can cause a failure. Get an X lug wrench and use both arms to rotate the nut on. At the very least when tightening use your free hand to grab the wrench and apply opposite force than the tightening force at the end of the lever.
 
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Just because some got away with 200# on their studs doesn't mean you will not encounter a stud that fails at 130#

That is assuming your figures are correct. Depending on how you placed your weight on the wrench, you may have applied many times the force you believe you did initially.

A fastener being overtorqued for the better part of 8 years will be diminished. If you have been using your stated method for the life of this vehicle, you'll probably see even more fastener failures.

If I were spending my money, I'd buy new wheel studs, lug nuts and a torque wrench.

Start with the torque wrench...
 
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Roanoke Virginia
Yeah it seems it was pushed to its limit over torquing over time it probably just wore out. I’d never go more over the torque on purpose especially with steel wheels that don’t flex as much.
 
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British Columbia, Canada
Today, I was doing a routine tire rotation on the ol' 2012 Honda CRV, and was doing the final tightening of the lug nuts. The RF wheel was the last step. Cris-cross sequence on the 5 lug nuts, all tightened nicely but one stud would not bottom down. Tried to back off but the stud was snapped off.

Power tools have never been used on the car since I bought it new, and I'm the only person who did the tire rotations over the years. Always did manual tightening. Granted, I don't have a torque wrench, but I'm 150 lbs and apply this weight on the 9-inch long Honda tire iron, which equals 112 ft-lbs. I use a little grease on the studs, so maybe this amplifies the torque by 15% and makes it 128 ft-lbs. This is over the spec'ed 80 ft-lbs by Honda, but surely it is not enough to snap the stud. We've all read of cases on BITOG where 200 ft-lbs or more were applied and the studs were none the worse for it, right?

Looking at the damaged area, I see near the center some metallic grain that is perpendicular to the circumference of the stud. Any comments, guys? Metallurgy issue?
Your weight has nothing to do with how much torque you applied (unless you always balanced your body weight on the very tip of that 9" wrench for the final torque - which seems very unlikely).

That's a brittle torsional fracture. Looks to me like it's been over torqued.

There's a good chance you're about to have more of these failures. Now about getting a torque wrench ...
 
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1,565
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RI
If this is like most Hondas you’ll need to remove the hub the bearing either partially or fully to get the new stud in. And this is user error.
 
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It's not a metallurgy issue, but metal fatigue issue due to your method of tightening the lug nuts. I got myself a cheap beam style torque wrench just for dealing with lug nuts. Beam style because I don't have to worry releasing the tension when storing the wrench.
 
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5,005
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Los Gatos, CA
As others have posted, using better tools than the wheel nut wrench supplied with the car and your muscles is a better way to go.
Your wheel studs will thank you for it.
 
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Chicago
I've taken off a wheel that had all 5 lugs torque to some crazy way above 200ft-lb. I want to guess 400ft-lbs.

That car came to me with 75-100PSI in all 4 tires to start with. And then i was asked to rotate the wheels and found that crazy torque. I had a 1000ft-lb impact at the time that could take honda crank bolts out and it struggled with those lug nuts. Oddly enough no damage or stretching from what i can tell. I was almost for sure i would be selling the customer 5 studs and lugnuts.


I've also had one snap on be from normal tighten with a 12inch ratchet. So it can just be very random.
 
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