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On cats, lug nuts and torque wrenches

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Old 02-27-2015, 08:08 PM
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Default On cats, lug nuts and torque wrenches

no doubt, but one more time.

I had to remove the left rear tire today after picking up a friendly neighborhood nail. And, not surprisingly, the lug nuts were a nightmare. Two came off with no problem, one snapped where the nut meets the flange, the other two broke the studs. Any need to mention if the stamped steel covers survived?

Ok, no problem really. It's a second hand car and I actually expected to have this exact problem. Over the last 30 years I have changed countless tires, everything from big trucks to children's bicycles and I really feel that I am the only one on God's green earth that uses a torque wrench and anti-seize when working on machinery. Aluminum wheels seem get the worst since, for whatever reason, mechanics think they need to put the Kung-Fu death grip on the nuts. And as anybody who ever had to deal with a stuck lug nut on aluminum wheels knows, there aren't enough curse words in a sailor's vocabulary for the mechanic that put them on.

First off, with the stamped type of lug nut (Jaguar isn't the only one that uses them BTW) an impact wrench is exactly the wrong tool to use. It will destroy the cover every time. Use a breaker bar and socket only. And do use the correct size 6 point socket. 12 point sockets are evil, they should be banned by international treaty and said ban enforced by heavily armed UN peacekeepers. The same when replacing the nuts, hand tight, then torque with a proper torque wrench using a 6 point socket. Use a 19mm for metric, a 3/4" for standard, and so forth. But since we are talking about a Jaguar, metric only. Standard tools get to stay in the box for this one.

A dab of anti-seize goes a long way to preventing rust on the studs. Grease will work for a while, but by the time the wheel needs to come off again, the grease would have evaporated and it's back to rusty-dusty wheel studs. I use the common aluminum based anti-seize, but the copper based will do just fine. A small tube cost very little and will last for years, there is no reason not to have some in the repair box. Don't neglect to do this or it won't matter how carefully the nuts were installed the last time the wheel was off.

Results may vary, but for the last 29 years or so I have never broken or cross threaded a lug nut, nor have any wheels I installed come loose or lug nuts damaged in removal. Proper on this time, easy off next time- no worries in the middle.

Now then, I am off my soap box, the weekend is coming up, and I have 15 more studs to check...
 
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Old 02-27-2015, 10:49 PM
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And the Toyota one-piece lug nuts will happily replace the rattle-caps for a fraction of the cost!

Watch your torque, too! 90 # wet is about all the take!
 
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Old 02-28-2015, 12:02 AM
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Ozzle, be careful applying the anti-seize to the studs. By applying this, you are changing the "slipperiness" of the stud/nut joint. What happens is this causes the needed torque to get proper clamping force to drop. So, if you torque something to say 100 ft-lbs with a dry stud/nut combo, you may only need to apply say a 70 ft-lbs torque if you apply anti-seize (the exact value is dependent on the product applied). If you were to torque the nut to 100 ft-lbs and use the anti-seize, you can potentially over torque the stud and break it off. So, just a heads up.
 
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Old 02-28-2015, 06:43 AM
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Yes, good point Thermo. Torquing a bolt requires some knowledge of what torque is and how it applies to machine bolts in specific situations. Some specs call for a dry nut, others require the use of a light oil. Using a socket extension also changes the torque value and the setting on the wrench has to be adjusted accordingly. And it's right and proper to ask the mechanic working on your cat to present his torque wrench to you so you can check the calibration date. Perhaps I should write a short primer on how to correctly use a torque wrench someday.

Contrary to first logic, torquing a bolt isn't so much about getting it tight enough, but preventing it from being over-tightened and either breaking off or warping whatever it was it's clamping. There is a balance point where the fastener is stretched enough to hold, but not so much it's in danger of failing. MOST of the time, about 99.99999% of the time, bolts and nuts are WAY over-tight because the mechanic working the job is either lazy or doesn't know the proper way to do it.

And don't get me started on oil drain plugs.....they have a torque spec also.
 
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Old 02-28-2015, 09:07 AM
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I usually wire brush the studs, and then torque the nuts. I really like the design of the Jag cushioned lug nuts, other than the cheap caps on each nut. My torque wrenches are recalibrated every 6 months mainly because I am an **** SOB, but also because I worked on highline cars, and you never wanted to build an engine with a torque wrench that wasn't dead nuts on. It only costs a few bucks each time, and without doing so renders the tool useless. Need I mention, after using a torque wrench, you should return the setting to zero, so you don't mess up the tool.

My major problem has been getting the aluminium wheels off the steel hubs. Aluminium is a horny metal, that likes to mate with other metals. After spending much of my young life beating aluminium wheels off steel hubs, with dead blow sand filled rubber hammers, I started putting a moly lube on the wheel, where it contacts the hub, and that includes the center, after the corrosion is removed from the hub and wheel center. Now my old *** can remove a wheel in no time. I beat them off every car I get with alloy wheels, and treat the surfaces.

If an aluminium wheel is stuck on while changing a tire on the road, you can also loosen the lug nuts around 4 revolutions after breaking them free, and drive a few feet, while turning the front wheels. This will usually break the wheel mating surface free, without doing much if any damage to the rim, your hands, clothing, or your back......Be cool.....Mike
 

Last edited by mrplow58; 02-28-2015 at 09:26 AM.
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