I thought that overtorqueing lugnuts can warp rotors. My father doesn't seem to think so. Who's right?


Roguls,
New York, USA

You are right...this time...
Incorrect lug nut torque-ing can most certainly warp rotors, as well
as tire rims. Not to mention broken lug nuts too.
Replacing those on some FWD cars can be difficult and expensive.
I have seen "tire Jockeys" use the same impact wrench setting for All
the cars. No matter if they are working on Yugo, or a big Truck.
I guess they are making sure the wheels don't come off...

When cars were much larger and there was more room, the brake rotors were bolted the the back side of the hub. Torgue didn't matter at all, except for damaging wheels and stripping the occasional thread set.

Now, cars are much smaller and to save space, the manufactures, most anyway, sandwich the rotors between the hub and the wheel. That's where the problem arises.

So, from your dad's perspective, and his frame of reference, he's right, and from yours, you're right.

The bottom line is, on the 700's, overtorquing causes the rotors to warp, but not on your dad's 70's Ford LTD.

...... ..that debate here,but after many years of experience,I think people are too quick to blame the air wrench[and the person behind it]

745T 1990

Personally I think that an impact wrench is fine if you are careful about how you use it. And attentive. It's not that hard.

Phew. I've been afraid to say that for a long time here.

But I still put on my own alloys with a 1/2" breaker bar and pull them evenly. I guess I'm just THAT anal about it.
--
Chris Herbst, near Chicago, IL. 93 940, 91 240, 90 240, 88 740, 87 240

Technically, dad wins. The tightening of the lug nuts does not warp the rotors. Uneven torque on the lug nuts can cause uneven pressure on the rotor. The warp is caused when the heat from the breaks causes the metal to relax or stretch when it evens out the stress from the nuts. More important than torque settings is the evenness of the torque. This is acquired in a star type sequence at 5 lb intervals above 50 lbs. One of the biggest complaints at the tire stores I managed was over torquing. We had a torque wrench at every bay, but it was next to impossible to convince the guys to use it correctly. Typically, they would run them up with a gun and then "check" with the click type torque wrench set at the stated ft lbs. If it clicked, it was good enough. Proper torquing would have the nut move, if even slightly, through the click. As a foot note, always check wheel manufacturer torque specs and not vehicle manufacturer specs. Many aftermarket wheels are of various alloys and have lug nut seats, or lack thereof, and compress differently than other wheels.

Agree to go dutch with dad on a beer on this one and put your efforts into debating the Super Bowl......

Leonard

I had tire shops trash the rotors on an Olds, and a mercury before I started carrying torque wrenches with meat all times.

What's the meat for?

Sorry, I couldn't resist.
--
88 765 w/2stage boost & G-valve @ 14 psi

Yea, torgue wrenches with meat. What the hell is that all about?

WHAT IS "TORGUE"? Is that something for meat?
--
88 765 w/2stage boost & G-valve @ 14 psi

Incorrectly torqued lugnuts certainl warps rotors. My car is a perfect example.

You win!

The most common cause for warped rotors is when tire jockeys blast the lug nuts on with an impact wrench haphazardly.

I use an impact wrench on setting #1 to pre-seat the lug nuts, and then either finish off with a 1/2" breaker bar or a torque wrench if I feel fancy. Once you get good at it, you can feel what torque you're applying and not overdo it.

To be honest, I use the impact wrench a lot on a second trip over the lug nuts on #3 setting, for the same number of hammers on each time. Always works, but again, only when you pay attention to it.
--
Chris Herbst, near Chicago, IL. 93 940, 91 240, 90 240, 88 740, 87 240

You win!!!!!!! Not only Volvos, but other vehicles with disc brakes.
dick

Score one for the boy

You definitely win. Over tightening, or uneven tightening, will warp the rotors on most (if not all) modern cars. Ask your local tire vendor why they use a torque wrench to tighten the lugnuts. Its because they got sick of replacing people's rotors for free!

bruce

Overtorquing does warp 700 series rotors. May not be the case in all cars, but it's a sure thing in Volvo's