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Posted: 10/11/2004 3:32:03 AM EST

Several months ago I had a local shop replace the rear brake pads on my wife's car. Since then, the few times I've driven it, I've noticed some shimmy when slowing down (braking). It wasn't shaking the steering wheel like warped front rotors can do.

Stupid me, I don't think "brakes" since the pads are fine and I don't know of any stress that might have caused rotor warpage. I'm thinking maybe the tires need balancing or something.

Recently, a friend suggested that overtorquing the lug nuts can warp rotors (anyone heard this?), and that rotating the tires could provide some insight into tire balancing as a possible cause. It's about time to rotate the tires anyway, so I decide to do that yesterday.

Well, turns out I can't break loose the rear lug nuts! You'd think a place called "Brake King" would know how to torque lug nuts. Spec torque is only 65 ft-lbs, and these puppies don't wanna break loose with a half-inch drive breaker bar. Way, way too tight. I didn't force the issue - I'll take it back in to the shop and talk to them.

On the one hand, the evidence suggests to me that their overtorquing has caused the problem. On the other hand, it's been about 3.5 months since they did the work, so I expect resistance on their part.

Any experience to relate or advice to offer?

Thanks...


Link Posted: 10/11/2004 3:36:05 AM EST
i could see that as a possibility- or they are rusted tight- a impact wrench will remove them. They definatley should be tourqued correctly- i would bet that they just cranked em tighty with the impact wrench (bad)
Link Posted: 10/11/2004 3:36:58 AM EST

Originally Posted By DrMark:


Recently, a friend suggested that overtorquing the lug nuts can warp rotors (anyone heard this?),




Yes.
Link Posted: 10/11/2004 3:38:26 AM EST
That sounds like exactly what's happened. Many cars today give very exact torque values for wheel lugs just for the reason you cited. My local place stamps your work order and the tech writes in how much he torqued the lugs.

Unfortunately both of us know that the odds are against you on this one. A letter sent as high up the management ladder as you can get might help.
Link Posted: 10/11/2004 3:51:49 AM EST
You will most likely never see a brake tech torque lug nuts properly at your typical service center. Not evenat the dealerships where you are billed $75 an hour.

Everyone uses the "rattle wrench". And the torque setting is a one size fits all, tight as it will go.

When I need tires, I take the wheels, sans vehicle, to the tire store and have them mounted and balanced. Then I put them back on the vehicle and properly torque the nuts.

Been doing it this way for 20 years, and I do my own brake work as well.

Just try removing the nuts (the tirestore guy tightened) some cold, rainy night when you or your wife has a flat.
Link Posted: 10/11/2004 3:59:41 AM EST
A shop that I once worked at had what were essentially small extensions that fit between the impact wrench and the socket. These extensions were made to give at a specific torque so that the tech could plug away with the impact wrench and not overtorque the bolts.

A customet once came in claiming that I overtorqued the nuts on his car and that they could not come off. I then too a regular 1/2 inch rachet and easily removed the lugs.

ktm500
Link Posted: 10/11/2004 4:00:09 AM EST
Yes, overtorqued lug nut can warp a rotor. I'd go back and verbally beat them about the head. If loosening and re-torqueing doesn't correct the problem, the rotor(s) may be permanently distorted. Point out that it's also a liability issue for the shop, as fastener failure can occur from overtorqueing. I work in Engineering at a major urban transit operation. We torque all lug nuts (450 ft. #'s !!) and then re-torque several times afterwards.
Link Posted: 10/11/2004 4:04:47 AM EST
There could also be some sort of debris (a lump of rust maybe) under the rotor. This would cause it to sit at an angle rather than properly seat to the hub.

ktm500
Link Posted: 10/11/2004 5:53:57 AM EST
Mechanics seem to over-torque lug nuts all the time. I need new rotors on one of my cars because of them.

GunLvr
Link Posted: 10/11/2004 2:54:09 PM EST

Brake King Manager: "Overtorqueing the lug nits can't warp the rotor. Only heat does that. Besides, our mechanics never put more than 80 ft-lbs on the lug nuts."

Funny, yesterday my torque wrench told me the front lug nuts were around 80 ft-lbs, and they went on and off fine. The rear one wouldn't budge. Of course, the mechanic had no trouble loosening them for me with his trusty ol' huge impact gun.

Oh well, Brake King of Newport News is off my personal list of approved businesses™.

That was the wife's car. Incidentally, I took my car to Sam's Club for new tires. Sets of torque sticks are hung on the wall, accessible from each bay. The mechanics use them (I watched), and my receipt is marked with the torque. Fine experience.

Link Posted: 10/11/2004 2:59:17 PM EST
I always heard that could happen as well, but have since heard other things. One rotor maker says that no matter how strong you think your wheels are, even high strength ones, they will warp before the rotors. Kind of makes sense since most wheels are thinner steel or aluminum.

Another issue that I didn't know is that almost all "warped rotor" situations are atually uneven deposits of pad material. I can find links if you want to read up on it.

Did they turn your drums or rotors?
Link Posted: 10/11/2004 3:11:25 PM EST

Originally Posted By jvic:
Did they turn your drums or rotors?



Turned the rotors - smooth braking now.
Link Posted: 10/11/2004 3:19:34 PM EST
When I was a young man I had a bunch of Hondas. They would warp rotors like crazy if I did not use a torque wrench. Go to the sore and buy a torque wrench and torque them yourself. I NEVER TRUST THE SERVICE PLACES TO TORQUE IT. I have seen too many bang them on a forget.
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