Torque setting for lug nuts
 

At the autox this weekend a bunch of the other drivers watching me retorque my racing wheels (stock 93 R1 with Victoracer 700s 245x45x16) got into a discussion about the correct settings. I was torqueing to 65lbs, a couple of guys said I needed at least 85 to a 100 to withstand the added strain, while a couple said that would infact damage the wheel. What do you guys use for your torque settings for autox??

Use the stock torque settings (from the manual), don't overtighten the lugs.

80lbs

72-76lbs sounds just about right to me

more torque than a ricers civic!

80 for me

I use 65 foot pounds; it's within spec that the manual gives.

There is no need for more torque. Too high a torque will cause the lugs to bind after hard running because as the brakes get hot the hub and rotor expand putting even more tension on the studs. Because of this always wait until brakes have cooled before changing tires.

An aluminum wheel with tapered seats such as the stock FD wheels have will grip the lugnuts just fine at the specs recommended in the manual.

If you change tires often put a little antiseize on the studs. I do it once or twice a year and it has completely cured my problems with lugnuts seizing during removal and breaking wheelstuds.

80 for my fc

If you are changing your wheels often, I would use less torque because you are constantly putting new strain on your studs. Lug nuts are the most over-tightened part on all cars. There is no need for them to be more than 85 ft lbs.

antiseize changes the torque that you're applying to the stud.

75lb for me

What torque would you recommend if you are using antisize on the threads? I'm pretty sure the factory specs are for a dry lug with a dry nut. Using antisize would reduce the friction in the threads and require more torque to get the same clamping force (wheel to hub) and the same stress in the lug.

When tightening a bolt, your ultimate goal is to attain a certain clamping force between the two mating surfaces. Factory specs only list the torque settings required to get these clamping forces. A torque setting is really a pretty crude way of doing this, as there are many more things that come in to play besides the torque, that affects the ultimate clamping force. A torque wrench is still the easiest way to come close, but it is still not a very accurate way of attaining the correct clamping force.

- Cooper Lacy

Bolgona.

The torque you're reading comes from the friction between the steel lugnut and the aluminum conical seat of the wheel in this case. Antiseize on the threads has no effect on this at all and in fact when torquing ANYTHING it is best to ensure the threads of the bolt are lubed.

Your Mazda repair manual will in fact instruct you to apply oil to the threads of many of the most "important" bolts (such as the tension bolts) before torquing them.

A common misconception that is always wrong. When you torque a bolt you are not only reading the force between the threads and the nut, you're reading the force between the nut or bolthead and whatever tightening it "mashes" it up against. In this case it's between the nut and a wheel. It could also be a nut and a cylinder head, or a bolt head and the rear cover in the case of our tension bolts. Lubrication of the bolt threads is actually advantageous because it ensures you're reading the friction between the nut and the part, not the friction on the bolt threads. Anybody who is anal about correctly torquing bolts (such as engine builders) will always be sure the threads have been chased and oiled before the torquing operation in order to ensure drag from the threads is not showing up in the torque reading.


This is correct but that clamping force really has nothing to do with torque on the bolt/stud. Bolts are elastic and when loaded there is an ideal amount of stretch for any given bolt that will provide the highest clamping force without overly straining the bolt or the part and causing it to fail. Since bolts are elastic we can compute that a given amount of force is required to stretch a bolt x amount and the amount of stretch is directly proportional to the amount of load the bolt will apply (up to the point of failure anyway). So if we know how much load we wish to apply we can compute how much stretch is required for a given bolt/stud. We can then take the friction of our materials into account and come up with a torque value that will produce the required amount of strain on the bolt/stud.

Torque wrenches are perfectly accurate for being certain the bolt in question is stretched correctly. As long as the threads are not goobered most of the drag on the bolt is a direct result of the pressure between the bolt head/nut and the part. Since the engineer knows what specific bolt he is using and he knows he has a steel washer under it, or a machined piece of aluminum or a copper crush washer or whatever else he knows how much drag will be on the bolt when it is tightened and he can quite easily give us a torque setting that will stretch the bolt a given amount.

The only thing more accurate then a torque wrench is physically measuring the stretch of the bolt or stud. This is either difficult or impossible in most cases. First you must know the elastic specs for that one particular bolt and you won't have them unless the manufaturer supplied them. Second you must be able to get to both ends of the bolt in order to measure it with a caliper. For any bolt going into a blind hole this is impossible. The most common thing I can think of where elongation is measured directly rather than using torque are connecting rod bolts in high performance engines. Realize a torque setting on a nut is also being used as a measure of bolt elongation, though it does this indirectly.

Nice reply, Damon. I don't know where these misconceptions are coming from. Dry torqueing is not recommended.

mmm...my FSM says not to put antiseize on the hub bolts...

Yes, reflux, but you CAN lightly oil the threads before torquing. Anti-seize is for nuts that will taken off and on repeatedly. Not germaine to a rotary board, but you ALWAYS lube head bolts before torquing. The same procedure applies to almost every threaded fastener.

Right. I wouldn't bother with anti-seize on the studs of any "normal" car but I literally change tires half a dozen times a month or more and was having stud breakage problems. The threads on the studs would fatigue, a small flake would come off and then jam when you tried to remove the lug nut. It would come off a turn or two just fine and then the small broken piece would jam in the threads and force you to twist the stud off in order to remove the lugnut. I had this happen no less than 4 times and that was with always using a torque wrench on the lugnuts. Anti-seize has completely cured my problem and no FD owner should be without a tube anyways ;)

Amen! I broke 4 sockets yesterday trying to get the lug nuts off of my front wheels.

Matthew Walsh

I've always used 65 ft*lbs on my RX-7s and never had any problems.