Impact before? Torque after?

I hate touch pads! I asked the owner of the tire shop to be sure and have the lug nut torqued. He said no problem. They do it by hand. Well I have been thinking about this since yesterday when they did it. The guy working on the truck cinches all the lugs with an air impact wrench ( I had the tires rotated too) then goes around and checks the torque with a torque wrench. He didn't just snug it with the impact he tightened it all down. Like I said. I'm no mechanic or tire guy. But this makes no sense to me. I think I should go home and loosen everything and re-torque according to the manual.

What do you guys think?

Ed Dowdy Fithian IL

Yes you should, unless the guy was using a torq-stick on the impact.

Denny

No looked like half inch gun with socket on it. But I'll call and make sure.

Ed

If the specified torque was reached (or exceeded) using the impact driver, using a torque wrench afterward would serve only to verify that the lugs are torqued to *at least* the specified torque. However, the specified torque likely has a *range* of values (ie 65-70 ft/lb). If the torque wrench didn't turn the lugs, they're overtightened. It sounds like this is what happened to you. Aside from making it difficult (or impossible) to change a flat alongside the road, there's the potential to do damage to the wheels, nuts, lugs, and/or rotors.

FWIW, even when I've specified it as you have, I've never found a tire shop that properly torques lug nuts/bolts. The last time I had a tire shop install tires/wheels ('69 Barracuda) , I specified they not use an impact driver at all and that they must torque to the 55 ft/lb specification using only a manually-operated torque wrench. They torqued the 7/16" lugs to over

150 ft/lb (the limit of my torque wrench)! If I can avoid it, I no longer let tire shops install tires/wheels.

Bryan

I called the guy. He said bring it in Monday he would gladly loosen and retighten them. I think for my own edification. I'll borrow a friends torque wrench and do it myself. It sure looked to me like they were being way over tightened. Like you said. If the nuts don't move with the torque wrench they're tightened to "at least" that torque. Who knows how far beyond.

Ed

Not always so, the only time a torque wrench reading is accurate is when the fastener is moving. It takes more torque to get a stalled fastener moving than the actual torque when it stopped.

IOW, if the desired torque on a fastener is 60 ft. lbs. and the fastener is actually torqued to 55 ft. lbs, it might take 65+ ft. lbs. of torque to get the fastener moving again. Therefore, if the fastener doesn't move after applying a torque of 60 ft. lbs. it doesn't verify that the desired torque had previously been reached or exceeded.

Excellent point - that has never occurred to me. I guess to be sure it would be best to loosen them somewhat and "get a running start" to the proper torque.

Thanks for the correction. The OP should check the torque it takes to make the lug begin turning. I get the feeling it'll be a *bunch* more than the spec.

It's a good idea to spot check two lugs on each wheel. See if you can get em off with a hand wrench. Cause that's what you'll likely have with you when you get a flat tire. Unless you're like me and always carry a breaker bar and deep impact socket.

Yep, that's what I do. Impact wrench to loosen, and torque wrench to set em back on.