Lug nut torque & warped rotors

My wife's 2003 Grand Cherokee fell victim to warped rotors, but after completing the repairs, I'm surmising that her driving style didn't cause the problem. While removing the lug nuts with a breaker bar, I felt a disparity in the effort required to loosen them. Hmmm. That can't be good. I wondered what the torque was on the other wheel, so I used a torque wrench to loosen the lugs. Torque varied from 80 to 125 lb/ft on the R/F wheel! Just for safety's sake, I checked the rear wheels. Same sad shape. Torque was all over the map. Moral of the story - when the dealer is doing warranty work (power window) and asks if you want your tires rotated - tell 'em "No, thanks" - unless you can oversee the job. Incidentally, the old rotors and pads had 29,000 miles and wore evenly, with no glazing or hot spots. The pads have 5/16 of friction material left. My money says that the dealer's tire-jockey has caused me (and likely many others) to suffer from warped rotors. Intentionally, perhaps? Hard to prove. Word to the wise - the 2003 WJ has rotors made of soft cast iron. Inattention to wheel torque can destroy them in a heartbeat.

Reply to
klutz
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It is well known enough that it had to be done on purpose by the $tealer.

I most certainly would bring the invoice with the mileage on it back to the $tealer and be wanting free rotors, if not the install too.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain
125 ft-lb seems like a lot, too. What is the recommended value?

Earle still top-posting

Reply to
Earle Horton
95-110 off the top of my head.

Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ

Reply to
Dave Milne

WJs - 85-115 ft lbs

Reply to
billy ray

I hate to be Devil's Advocate here, but 80-125 quoted by the original poster is not too far from 85-115. Perhaps the rotors warped due to some other cause, and he is seeing the result in disparity of the effort required to loosen the lug nuts. In the ideal world you would want to use a star pattern and a torque wrench. In the real world you want to get the wheels on and the vehicle out of the shop as soon as possible. It is impossible to say what they do in that shop, unless you work there, or are a lawyer who has received a lot of complaints about them.

Earle

Reply to
Earle Horton

But the torque for each lug nut should be the same, whether it's 85 or 115. It's such a known issue that uneven lug torque causes warped rotors that most likely it was caused by the last person to work on them.

Reply to
Matthew Macchiarolo

That range means 'all' of them should be at 85 ft lb 'or' at 115 ft lb. They must be the same, not one at 85 and the next at 115, then the next at 85, etc...

having some at 80 and some at 125 means it was not even slightly torqued. Even a crappy torque stick (that will warp rotors for sure) should be better than that.

Mike

Earle Hort>

Reply to
Mike Romain

Thanks for the insight. Maybe my explanation was unclear. The five individual lugnuts on the R/F wheel were torqued to 80, 98, 100, 113, and

125. Each of the rear wheels had the same random torquing, too. Perhaps the tire jockey used an impact that wasn't calibrated, perhaps he/she used a torque stick improperly, perhaps he/she doesn't own a torque wrench. In any case, he/she should know that all five lugs on the same wheel must be torqued to the same spec. I wouldn't have any heartburn if all 5 lugs were torqued to 85, or 115, or any setting in between - as long as they were all torqued to the same spec. Whichever he/she deemed proper, just stay with it. If a tire jockey can understand the instructions on a shampoo bottle - wash, rinse, repeat - the methodology for torquing a lug nut shouldn't be an abstract concept. The local Jeep dealer won't see my wife's WJ again, and the owner will be aware of my dissatisfaction very soon. There are a half-dozen other dealerships within a short drive.
Reply to
klutz

Problem isn't the actual torque so much as the differential torque between the lugnuts. Just to keep it simple, I tell my kids and the tire jockies doing any work on mine that 100 ft-lbs +- nothing is the number I want used. I've won several free rotations and even an alignment betting shop owners that their magic torque sticks on the air wrench cannot set the torque on any wheel to be within 10% on a

5-lug wheel.
Reply to
Will Honea

The rotors on your GC are made from two parts, the rotor, and the "hat". The hat is the part of the rotor that the wheel studs go through and your wheels bolt to. Further, the hat of the rotor rests flat against the wheel hub assembly, and you'll not warp that with 250ft. lbs of torque, much less the

125 you specified finding. The hat uses a different type of metal from the metal in the rotor, specifically to keep lug nut torque from being an issue with the rotors.

Jeep changed over to this type of rotor during the first series of GC and has used them since.

Lug nut torque was not the cause of the warpage on your rotors, hasn't been an issue in brake rotor warpage for years, but the general public won't let go of the idea.

The tire installer is not to blame.

The rotors being too thin to start with, along with driving habits, stop and go or city driving, and overdriving the brakes (driving too fast, stopping at the last moment) are the most often the cause of brake pulsations, like it or not.

The variations in lug nut torque are not out of line in the real world, rust, contamination, imperfect threads, grease, and dirt all affect the torque of the lug nuts. In perfect, laboratory conditions, with perfectly clean studs and nuts, lightly oiled, and a perfectly calibrated torque wrench, you might get 'em close, but that's not the real world.

By the way, with aluminum or magnesium wheels, lug nuts should be retorqued after driving 50 to 100 miles. ALWAYS.

Spdloader

Reply to
Spdloader

Reply to
L.W.( ßill ) Hughes III

Reply to
L.W.( ßill ) Hughes III

Even the local tire discounters only use torque sticks to get them close and then a hand torque wrench for final tighten... in a star pattern even. If a particular torque stick or wrench is off calibration it would not produce such widely varying values, it would just produce values off from absolute torque but a heck of a lot closer to relative torque. Unless they also lubed the things.

Will Honea proclaimed:

Reply to
Lon

Your explanation is clear, but difficult to accept.

If the manufacturer changed the rotors to a 2-piece design with dissimilar metals to guard against problems caused by over/under torquing, why in the world have they continued to ignore the cross-section thickness of the rotor? I agree that a thicker rotor (e.g., Brembo) will minimize the probability of warpage. If Jeep's engineers were genuinely concerned about the component, they would have re-engineered all known weaknesses, including warpage. I have to applaud Jeep's technology of rotor assembly. The joint between the 2 rotor pieces is absolutely indetectable to the naked eye.

Jeep recognized the advantages of the Akebono caliper in 2002. When were the rotors changed to a 2-piece model?

If that's true, why does Jeep provide a recommended torque range for lug nuts? Service procedures would be simpler for everyone if the manufacturer's specification was "85 lbs/ft minimum, user selects maximum".

You say that random torquing wasn't a contributing factor, so that makes the tire installer's methods sound? Hell, even the tire busters at Costco use a torque wrench. If it didn't matter, would Costco bother?

Not in this case. The Jeep is babied. Driving habits are excellent. A Ford Thunderbird we owned previously (which was notoriously known for rotor warpage) didn't exhibit any brake problems in 40,000 miles, likely because of proper driving habits.

I guess I'm pickier than most, because I refuse to use an impact wrench on the lug nuts of any of my vehicles. Interestingly, the Jeep is the only vehicle I've owned that needed rotor replacement before it needed a brake job.

You're right about that one. I learned that back in the 70s, when I worked for Chrysler. I still have the same Snap-On Torqometer that I used back then to torque lug nuts, including vehicles with left-handed threads on the left side.

Reply to
klutz

Klutz and Spdloader,

Composite rotors used for several years on Jeeps were not installed by the factory to lessen rotor warping. They were a cost-reduced and significantly lightened rotor that warped so easily that Jeep went back to all-cast rotor. They were so light in weight that they weren't able to resist warping from both heat and uneven lugnut tightening. Newer Wranglers and JGCs have all-cast rotors that are far better able to resist heat and uneven-tightening induced warping.

Jerry

klutz wrote:

Reply to
Jerry Bransford

Apparently you assume I was just making it all up.

All the information I gave you was straight out of the manual from a Chrysler sponsored school, in order to receive my instructor certificate in brakes and front end, not that it makes me the authority on it, but the information never let me down when training my own techs.

  1. To keep costs down, and 2. Cut into the metal with a brake lathe and you'll see the difference.

Let me clarify, the change was made by the aftermarket, somewhere around

1995, I don't recall the exact year. 1996 Model year Jeep GC had them from the factory. I left the automotive industry in 2003, including the instructor field. I don't know what changes have been made since.

To keep the wheels from falling off.

I never said his methods were sound, I don't know what methods he used, other than your description. I said he wasn't to blame. If the rotors warped with that minimal amount of torque, then they were the culprit all along, not the guy who tightened them.

Costco "bothers" in order to keep the wheels from falling off and getting sued. It happens more than you think. W/O's, (wheel offs) were the number 2 problem with a vehicle with "mags" after a brake job for comebacks, right behind brake squeal as complaints go for #1.

There are exceptions to every rule. My wife bought a new '04 Explorer. Warped rotors within the first 300 miles. I was allowed to inspect them after they were replaced. Both had stress cracks, obviously manufacturing defects. Possibly an alternative cause for your problem.

Then you don't know about the Ford Explorer from it's inception until about

2001.
Reply to
Spdloader

Wrong or right, my information came from a school Chrysler gave on their braking systems I attended in 1996.

Cost is most often the driving factor, I think. Spend the least they can get away with.

Spdloader

Reply to
Spdloader

Spdloader did pass the time by typing:

I run stillen rotors on the ZJ after the OEM pieces of shit gave way and warped.

As a rule I never let anyone torque the lugnuts but me. I even take my own torque wrench to the tire dealer and tell them to spin the nuts on by hand and I'll finish them off. No if's and's or but's.

The other thing to remember is the types of lugnuts. Cone, flat, and shoulder. Crank the wrong ones too tight and you can crack the rim.

As the wrencher who taught me said, "Air guns are for taking stuff off if your too weak to do it by hand." :) Asshole, yes, but he could have taught a monkey to yodel.

Reply to
DougW

I'm gonna say here that the torque required to break the lug nuts loose probably won't have any relation to the torque that was used to tighten them. You are having to overcome the friction between the nut and the wheel, to break them loose.

-- Old Crow '82 FLTC-P "Miss Pearl" '74 XLH chopper(somebody else's baby now) BS#133, SENS, TOMKAT, MAMBM, DOF#51, DH#2 "There's only 1 RE"

Reply to
Old Crow

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