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      12-01-2012, 11:07 PM   #1
Mooreski's Avatar

Drives: LMB '09 E90 M3
Join Date: Sep 2007
Location: Portland, OR

iTrader: (1)

Ok to use impact wrench on lug bolts?

I was always told growing up that you should never use an impact wrench on lug nuts / lug bolts. Is that an old wive's tale that isn't true with a new gen of impact wrenchs and 'torque bars'?

The background: Swapped the steelies and snows onto our 'battle wagon' tonight. It's a '10 Jetta Sportwagen with steelies, snows, a cargo box and a ski rack. I was giving my fiancee the how to and was laughing when she couldn't get the lug bolts loose. I stopped laughing when I couldn't either. Kind of surprising. I was even more surprised when I started looking and both driver's side wheels were missing a lug bolt. Note that she had a service with tire rotation 1.5 months ago.

Kind of worried, I grabbed a torque wrench to see how tight the bolts were. I had it @ 125 ft-lbs and had to push well past that to break the lug bolts for the 4 remaining on each of the driver's side wheels. Similar on the passenger side, except 4 were tighter than hell and 1 was finger loose on each passenger wheel.

I called the dealer to ask how they did their torques, manual calls for 88 ft-lbs. He said it depends on the tech if they use a torque wrench or an impact wrench with a 'torque bar' (in quotes because I'm not really sure what it is. A bar that flexes to limit torque?). I had always been told never to use an impact wrench, which he didn't agree with. He thought it was fine and had never heard that an impact wrench is a no-no.

I'm asking for all new lug bolts. I think the ones that were on there got torqued all to hell and don't like the idea of using them again. It seems obvious to me that they were over-torqued based on how hard it was to break them loose, but should I bring up the impact wrench argument?