Lug nut torque & warped rotors

This idea has some support in physics, where the difference between dynamic and static friction (sometimes called "stiction") is well known. When you are tightening a fastener, you are working to tension it against whatever is being fastened, but also working against the dynamic friction "between the nut and the wheel", in this case. Once you let go of it, additional force is required to break it loose, because static friction is in all cases (that I know of) greater than dynamic friction. This is true for a nut that has just been tightened, but after you drive the vehicle a few miles and it has had an opportunity to seat into the wheel, I suppose that the torque to break it loose can be anything.

Earle bottom posting now

Well, there we go right out of the horses mouth.

They (the $tealers) aren't even teaching the right way to fix the vehicles so they get the perfect 'planned obsolescence' on repairs.

Just give it to the 'new' guy to do, heh heh heh, he can screw their brakes and use the excuse he wasn't taught any better. "See, it says so right in the book".

What a pile of total and utter crap!

'Waaaaay' back in the 70's we were even taught we had to use torque wrenches on the new 'mag' and aluminum rims.

Car 'dealers' weren't known as outright thieves back then though and a 'service station' actually offered service.

Sorry, but....

My $0.02,

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

Interesting. I had Brembo disks on my Alfa, and they recommended against slow braking as it caused the disk to heat up and warp. In fact, the way you were meant to bed them in was by a few hard stop and go's

Dave

Tell me about it! I had the left rear wheel come off my '80 lwb Dodge van in the wee hours one morning (it was loaded heavily with vending machine merchandise and had a full 36-gallon plastic tank to boot) after getting new tires. I found that the lug nuts had to torqued to

100 ft/lbs. Twice more, I nearly all four wheels simultaneously until I checked with a dealer about the torque spec (turbine-style aluminum wheels). I found that it is a frighteningly common occurrence, with service station mechanics the usual culprits. It seemed every 5th or 6th person I talked to had had it happen to them or a family member. It isn't that critical on steel rims, however, and my '77 Cherokee only requires 75 ft/lbs.

From what I've been told, all the newer vehicles do, and at least some factory rotors are also too thin to be turned.

Dan

Once upon a long farking time ago a car I was sitting in was hit by a loose wheel. It was around midnight, my then-girlfriend was driving and we'd pulled up to a stoplight in the little burg that we lived in. I looked up the hill to our left and saw a tire and rim rolling down the street -- no car, just a tire and rim. It must have hit a bit of gravel or something because it hooked right and clipped her car just forward of the front wheel, making a honkin huge dent in the fender.

Driving up the hill we came upon a dazed guy leaning on his car in the middle of the street, the left front of the car was leaning on the ground where his tire and rim should have been. It was a good half mile from where his last lug nut fell off to where the tire hit us. The cops had a good laugh about it.

that's a kind of severe shimmy !

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

I can recall at least three separate occasions over the last dozen years in this town alone where a lost wheel on the freeway resulted in fatal injuries to occupants of oncoming cars and numerous demolition derbies iniitiated by the same villian. Loose wheels just don't seem funny to me anymore - although the look on the face of your girl's father was probably well worth a picture! "But Dad, here I was and .."

If they are all in the same town I'm guessing the same shop worked on all three vehicles.

Years ago I had some brake work d>

I was very surprised a few weeks ago when I had the local Wally World put new tires on the wifes ZJ and saw the final inspection by the manager included checking the lug nut torque. Does not mean that they did not over-torque but atleast they made sure they were tight.

Googling informs me that passenger vehicle wheel separation stats in the USofA are not collected, but that for commercial trucks the rate is in the range of 750 to 1050 out of about 350,000 truck accidents a year. That's a tiny number when compared to annual truck miles driven, but I'd still prefer to not be part of the on-coming traffic when a wheel separates from a vehicle at speed.

The Fed doesn't track it, but I promise, individual companies do, ie. Midas, Meineke, Monro, etc. In terms of liability and dollars lost.

Spdloader

There is also a phenomenon that happens between different types of metal. Corrosion, and chemical bonding CAN cause this, not that it did.

Spdloader

Guys who drive for a living are a lot more anal about checking their rides than most soccer moms. People working on commercial rigs are also just a shade better than the discount tire stores. Makes a big difference.

BTW, 3 instances in 12-15 years in a city of 300,000 with a major interstate running thru and more tourists than I like to think about is also a small relative number - but still 3 too many.