Contour Enthusiasts Group Archives Forums General Troubleshooting Why would over-torquing lug nuts warp rotors?

n/m

Uneven contraction and expansion as the rotor heats up and cools down during normal use.

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Louis Wang
Austin TX
1998 Black E0 #3826, lightly modded

Over tightening distorts the rotors. At first it might just be under stress, but eventually the stress can distort (warp) the rotor.

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Jim Johnson
98 SVT

Elizabeth????

We haven't heard from you in a while. Somebody said you got voted off.

I have been having some brake pedal pulsation for the past few hundred miles on my 99 SVT (13,000 miles). The rotors were turned by the dealer yesterday.

This is interesting to me in that I have been very, very, extraordinarily, anally careful about keeping the lug nuts torqued to 85-90 ft-lbs.

Generally speaking, I don't do much spirited driving, and am fairly easy on the brakes, although there have been one or two near-panic stops over the past two or three months. The service advisor suggested this could have done the damage.(??)

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Craig
99SVT black/tan
2725 of 2760

A couple of panic stops should not warp the rotors. I made panic stops (and starts) every day on my Honda Civic and it took 60,000 miles to warp the rotors. You should try to get new rotors from the dealer since your car is still under warranty. Turning them at 13K is too soon, and will only make them more prone to warpage (because of less mass). Your best bet is to install aftermarket rotors since Ford is too cheap with their iron.

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Barry Wolf
1996 Contour SE MTX Midnight Red, Parchment leather
Brakes: Bendix OEM size discs, Carbon Metallic Pads, Parking Brake TSB kit
Engine: New IAC valve, new EGR valve, new cat, new water pump, moose fix kit
Tranny: Redline ATF + Ford Friction modifier
Interior: Pioneer CD receiver, Pioneer speakers, Ford RS shift knob
Other: High beam bulbs in low beam position, new trunk vent
Current problem: leaking power steering pump

The stock rotors will not take a turning without going under spec. This happened to mine with only 40k miles.
I had them turn them right down to spec. After a few minutes of testing the brakes, they warped really bad. They where pretty cheap to replace though. Lesson learned.

Right on, Barrywolf and Chris. Not only less mass, but uneven thickness (in drum brakes, uneven wall thickness). Iron castings used to be aged to relieve stresses before final turning, but that's ancient history. Rotors and drums should very seldom need turning, though shops love to do it. Good reason to watch remaining pad (shoe) thickness. Soapbox clear.

The actual specified lugnut torque for the Contours is actually only @ 64 ft/lbs.

64? Doh! I was certain I had seen that it was 80-90.

Most tire stores should have some kind of "Tire Guide" book that will list torque specs and inflations for individual vehicles. The last time I looked it up, that was what I found. You may want to look it up again.

I stand corrected!!

Correct torque specs:
'97, early '98 is 64
'98 is 85
and '99 is 94ft/lbs

I think this whole overtorquing the lug nuts panic is over blown. I've had both the front and rear hubs and rotors off. The rotors mate up perfectly flat to the sizeable flange plate on the hub. If they are over tightend by 10-15% there's nothing to bend or warp as long as all the nuts are equally tight and tightened in a cross pattern. Sure there are some crappy rotors out there but an extra 5 lbs of torque isn't going to distort the rotor and flange plate enough to cause damage.

Correct, but we're talking about massive deviations like when tire monkeys use air hammers to tighten lugs. Those things are capable of 300 ft-lbs and the difference between lugs could be enough to warp your rotors in the long run. Worked it a garage before, I've seen it lots of times. Some of the more unscrupulous garages will tighten them with air hammers intentionally, knowing you might come back for a brake job...

Well, I decided that I am going to replace my front rotors and see what happens. I have about 50K on them now, and I did have them cut at about 38. I think that I will try going with some aftermarket rotors up front as I used aftermarket in the rear from Pep Boys. The way I see it, if I am going to dump money into my brakes (beoynd better pads), it will be to do a 300mm rotor and bigger calipers. (and that aint-a happening anytime soon!)

Thanks,
Andrew

I work at a car garage on my summers and holidays off from college. My hometown is one of those really small backwoods types... I mean, blink on the interstate and you miss it Point is, our garage has these cool things that are called Torx sticks (sp? Maybe they are spelled stix for the brand name, I don't remember) but anyways, these beauties attach to an air gun... they have different shaft thicknesses connecting the lug wrench and lug socket together. No matter how high you crank the air pressure, you can hammer on the gun all day and not exceed torque specs for whichever wheels you are working on because the shafts act like a torsion bar after a certain torque has been reached. I did this to my car while on the lift and hammered the air gun for a good minute on each nut and verified with an actual torque wrench. It torqued within one foot pound of the reading on the stick. I was amazed, but I don't see many tire shops having them. I wonder why not.....

Why the difference year to year?

Chris
99 SE V6 5sp

I was wondering what the source of the torque cindy used is. I searched my owners manuals last night to no avail.