[jpk]

Yesterday, I rotated the tires on my '03 linear. This was the first time the wheels have been off the car (I know - I probably should have done this at least 10000 miles ago...) As I typically do for all my cars, I gave the lug bolts a shot of lithium grease before putting them back, just to ensure they will come off in the future.
While torquing down the bolts for the first wheel I find that the bolts don't feel like they're torquing down propery - they get tight, but I can still turn them (I'm using an 16" breaker bar, so I do have a bit of leverage). I work my way around the bolts, and it just doesn't feel right. I can continue to turn them past the point I think I should be able to. I'm pulling pretty hard, but not any more than when I'm torquing the lug nuts on my Porsche or truck (If I had to guess, maybee 120 or 130 ft-pounds) One of the bolts snapped. Luckilly, I was able to back the bolt out.
After this happened, I found the torque spec in the manual (80 ft-pounds) and torqued the remaining lug bolts to that (more or less)
It seems strange to me that the lug bolt broke with a relatively low torque. Are they purposely designed to give at a low force like that? Could the grease have caused a problem? Has this happened to anyone else?

 

[ctrlz]

Bolts can be focally weak. The bolts on the 93 seem to rust, so I guess they are mostly steel. You want a high carbon content for hardness in lug bolts. The tradeoff is higher carbon can also lead to brittleness, and the bolt can snap.

I have always read the general recommendation to NEVER grease lug nuts or bolts. In fact, that sticking sensation and squeaking sound is often the mental cue I use to judge when it's tight enough. Like you, I use a 16" crossbar. Those give you a lot of leverage. So I run them down, then give them 1/8 turn or so. Not precise, but I haven't snapped one yet or had one that came loose.

Here's some stuff on bolts:
http://www.boltdepot.com/fastener-information/Materials.aspx

 

[voodoochile]

Did you use a torque wrench? It's hard to imagine breaking it at even 100ft-lbs, despite the reccommended 80. Grease is definitely a no-no on lug bolts or nuts, will make it a whole lot easier to over-tighten, and is especially dangerous if you are not using a torque wrench.

I'm speaking from similar unfortunate experience.:roll: