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      12-01-2012, 10:07 PM   #1
Mooreski
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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?
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      12-02-2012, 12:29 AM   #2
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Yeah you are right impact wrenches shouldn't be used on lugs. Some places use torque sticks to limit the torque on impact wrenches. I don't know how well this does or doesn't work. But frankly it doesn't take very long to do it right with a real torque wrench. Over torqued lugs can warp rotors, wreck your lugs/hubs, etc... Regardless, if the spec was 88 and you needed over 125 to get a lug off they did it wrong. Impact gun or not.
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      12-02-2012, 12:36 AM   #3
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Use an impact to remove, not to put on. Use a manual torque wrench to tighten to 88 ft lbs.
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      12-02-2012, 12:51 AM   #4
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By the book you shouldnt use it to torque wheel bolts, but in the real world everyone does it esp at the dealership. Their impact guns are calibrated to not over torque it.
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      12-02-2012, 09:00 AM   #5
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Quote:
Originally Posted by ~XxPornxX~ View Post
By the book you shouldnt use it to torque wheel bolts, but in the real world everyone does it esp at the dealership. Their impact guns are calibrated to not over torque it.

No offense but this statement is funny "Their impact guns are calibrated to not over torque it" can not calibrate an impact gun, too many variables , one is psi input into the gun and the other impacts per minute. Even torque wrenches when calibrated they are +\- certain percentage depending on brand and quality.

Torque sticks are not that accurate either, gun variables like how many impacts per minute it is set to and input psi.

Never use impact gun to install wheel lugs. The reason is uneven torquing of the lugs that could possibly warp the rotor hat causing vibrations during braking. Over-torqued lugs cause a problem for the owner if one gets a flat and the nuts can not be loosened with a tire iron on the side of the road. Others are stripped studs, cross thread and possibly others.
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      12-02-2012, 09:07 AM   #6
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Quote:
Originally Posted by slupie View Post
No offense but this statement is funny "Their impact guns are calibrated to not over torque it" can not calibrate an impact gun, too many variables , one is psi input into the gun and the other impacts per minute. Even torque wrenches when calibrated they are +\- certain percentage depending on brand and quality.

Torque sticks are not that accurate either, gun variables like how many impacts per minute it is set to and input psi.

Never use impact gun to install wheel lugs. The reason is uneven torquing of the lugs that could possibly warp the rotor hat causing vibrations during braking. Over-torqued lugs cause a problem for the owner if one gets a flat and the nuts can not be loosened with a tire iron on the side of the road. Others are stripped studs, cross thread and possibly others.
Theres torque level settings built into them, using them daily for a living they know how much is too little and to much by feel/sound. I worked at the benz dealer ship for a while just out of school. Just about every tech in there laughed at me when i first started and torqued each nut with a wrench.

Keep in mind these guys flag hours and the last thing on their minds is to take time on your nuts. The also make torque sticks (impact gun) for noobs that you often see use them at americas tires. With that said, if im at a shop and i see an unknown impact ft-lb ratings @ X psi i would never use it on my own wheels. Just lightly zip them down and torque by hand. I have my own gun and know its feel/sound.
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      12-02-2012, 10:11 AM   #7
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Quote:
Originally Posted by ~XxPornxX~ View Post
Theres torque level settings built into them, using them daily for a living they know how much is too little and to much by feel/sound. I worked at the benz dealer ship for a while just out of school. Just about every tech in there laughed at me when i first started and torqued each nut with a wrench.

Keep in mind these guys flag hours and the last thing on their minds is to take time on your nuts. The also make torque sticks (impact gun) for noobs that you often see use them at americas tires. With that said, if im at a shop and i see an unknown impact ft-lb ratings @ X psi i would never use it on my own wheels. Just lightly zip them down and torque by hand. I have my own gun and know its feel/sound.
Try to have an impact gun calibrated, you will get a good laugh out of the calibration house.

Torque settings? put more pressure in you get more torque, less pressure less torque. "feel/sound" is plain old laziness. I'm a mechanical engineer and have been wrenching on my own cars and with friends for almost 20 years. I have few impact guns and the settings and variables are very inconsistent every-time.

There is a reason why there are torque specs on bolts. DO NOT OVER-TIGHTEN THEM, bolt stretch and failure of threads when over-tightened. All wheel bolts are fine pitch threads they do not have the same strength as a coarse thread bolts.

Every-time I had a friend or family member call me for help changing a flat on the side of the road, the car was at a shop or dealership recently and they did a tire rotation. Guess what every-time the bolts were overtorqued by a wrench monkey/parts swapper with an impact gun. I bring my 24" breaker bar and a cheater pipe to get the wheel lugs off.

Wrench monkeys using impact guns to put on wheel lugs is plain old LAZINESS.
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      12-02-2012, 10:28 AM   #8
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Agree with posts above, it is WRONG to use impact to install lugs but everyone does it anyway. Impacts are for removal only!

I would argue that one could use an impact to install if one had a real light touch and was able to reliably just seat the nuts but not exceed say 60 lb-ft, then finish with a torque wrench - but that's a lot of "ifs".
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      12-02-2012, 11:22 AM   #9
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Quote:
Originally Posted by slupie View Post
Try to have an impact gun calibrated, you will get a good laugh out of the calibration house.

Torque settings? put more pressure in you get more torque, less pressure less torque. "feel/sound" is plain old laziness. I'm a mechanical engineer and have been wrenching on my own cars and with friends for almost 20 years. I have few impact guns and the settings and variables are very inconsistent every-time.

There is a reason why there are torque specs on bolts. DO NOT OVER-TIGHTEN THEM, bolt stretch and failure of threads when over-tightened. All wheel bolts are fine pitch threads they do not have the same strength as a coarse thread bolts.

Every-time I had a friend or family member call me for help changing a flat on the side of the road, the car was at a shop or dealership recently and they did a tire rotation. Guess what every-time the bolts were overtorqued by a wrench monkey/parts swapper with an impact gun. I bring my 24" breaker bar and a cheater pipe to get the wheel lugs off.

Wrench monkeys using impact guns to put on wheel lugs is plain old LAZINESS.
Just because there are reasons every bolt has a torque spec dont mean every mechanic in the world busts out a torque wrench for every suspension bolt either. A mechanical engineer dont mean you torque each nut hundreds of times a week for a living. Im not arguing with you, but only noobs would run and hold a gun on a nut for x amount of time to over torque it. Be smart with it, you dont have to be an engineer to know how much bolt stretching can warp the rotors. As i say this i leave my torque wrench in my trunk, yes ppl use guns some dont, simple as that.

Here these guys must be idiots to use a gun too right. oh no wait, they know the feel. Yes granted they do it for a quick race bla bla... but my point was skill/judgement.

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Last edited by #Tee; 12-02-2012 at 11:29 AM.
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      12-02-2012, 02:32 PM   #10
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Quote:
Originally Posted by ~XxPornxX~ View Post
Just because there are reasons every bolt has a torque spec dont mean every mechanic in the world busts out a torque wrench for every suspension bolt either. A mechanical engineer dont mean you torque each nut hundreds of times a week for a living. Im not arguing with you, but only noobs would run and hold a gun on a nut for x amount of time to over torque it. Be smart with it, you dont have to be an engineer to know how much bolt stretching can warp the rotors. As i say this i leave my torque wrench in my trunk, yes ppl use guns some dont, simple as that.

Here these guys must be idiots to use a gun too right. oh no wait, they know the feel. Yes granted they do it for a quick race bla bla... but my point was skill/judgement.

And that my friend is why I do all my work. Torquing suspension bolts with an impact gun and binding suspension bushings is bad and just asking for trouble. Also if some suspension components are torqued before being loaded at the ride height they could and will bind. Follow what the manual says not what the parts swapper does. Because they do it for a living doesn't mean that what they do is RIGHT by any means.

How do you know how much the bolt stretched if you can't control the amount of torque you put on it and how many times has that been done to it.

Those guys are not idiots, just a special design spindle, nut and gun. Racing applications are a bit different that they are over-designed to some degree and it has to last the race weekend. It is also inspected very often on top of that. Did you notice that that nut on the right of the F1 car had left hand threads and detents on the hub to hold the nut from spinning off by itself.
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      12-03-2012, 12:57 AM   #11
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I request torque wrench at the shop. No impact wrenches.
I had a moron at a shop gall the bolt on my M3 so bad I had to have it re-tapped and switched to studs.
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      12-03-2012, 01:01 AM   #12
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Thanks for all the replies guys. It'll be an interesting talk with the service manager tomorrow. Sounds like the consensus is that impact wrenches are a bad idea. Anyway it's cut, they were improperly torqued, two wouldn't be missing if they were torqued right!
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      12-03-2012, 11:02 PM   #13
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The Service Manager called me early this morning. He was very apologetic and agreed to give me a new set of lug bolts. He's shipping them so I don't have to drive 30 min out of my way to pick them up (100% his idea). He also offered a free oil change for the first service when the car is out of the free maint. period if I decide the bring it back. Gotta say, based on the SA I talked to on Saturday, I was expecting a bit of a fight. This guy caught me off guard in a good way.
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      12-04-2012, 11:45 PM   #14
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Quote:
Originally Posted by techwhiz View Post
I request torque wrench at the shop. No impact wrenches.
I'm sure they say 'oh yes, of course' while laughing in their heads. There's no way to prove they used torque vs impact at that point, unfortunately.
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      12-05-2012, 01:50 PM   #15
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i had a dealer up here mount and balance a new rear tire for me this summer. I switch to snows myself and use the prescribed 88 ft-lbs. When i went to put my snows on a few weeks ago the lugs on that rear wheel were WAY over-torqued. I'm a pretty muscular guy (5'8" ~200 lbs) and I had to practically STAND on my breaker bar to loosen them. In fact, I had to put the handle of my racing jack over the handle of the bar to get more leverage! so much for calibration of impact wrenches lol
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      12-06-2012, 02:46 PM   #16
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I've spoken to my garage, who has torqued them down so hard I needed a breaker bar to get them off, and their explanation was simple: "We over-tighten them because if they ever come loose and there's an accident, the driver will blame us because we touched them last. So we make sure they damn well wont come off."
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      12-06-2012, 02:54 PM   #17
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And that is why I do my seasonal tire changes myself.
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      12-06-2012, 03:44 PM   #18
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How do you jack the car up, did you make a thingy to connect to the car to provide a better jack surface?
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      12-06-2012, 04:22 PM   #19
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I actually have the factory jack that didn't come with the car (bought it from Tischer) because my winter tires aren't RFTs so I need to carry a spare and a jack.

I have yet to purchase a floor jack that is low profile enough to fit under the car, but there are plates available to adapt one to the factory jack points. I think I've seen it on ECS's web site among other places.
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