Is Torque a Property of Lug Nuts or Lug Bolts?

Question

I recently ordered some new rims and tires through the local tire shop. Because the tire shops almost never use a torque wrench on lug nuts, I am going to bring my new wheels home and install them myself properly. This brings me to the question:

1. Does changing wheels and lug nuts changes the torque specification? Or is the torque more a property of the lug bolt, which will not be changed in this case? As shown in the picture above, the Honda spec is 79.6 lbf-ft.

2. The wheels are Motegi Racing MR116s and I can't find any information online on what the torque specification is. Do alloy wheels all have the same torque?

I watched a bunch of videos but haven't found any that explain these two crucial points. So I am turning to you guys.

Please educate me! Thanks.

Honda Civic 2006 LX 4 Door 1.8L

Answer 1

It's really a property of both, but the bolt is the more important of the two. As you tighten the nut onto the bolt, the parts actually distort slightly.

When you tighten a lug nut onto a bolt, the bolt actually stretches, similar to a spring or rubber band, but on a much smaller scale.

This stretching creates tension that helps ensure the connection will not loosen. The nut also undergoes some distortion, as does the wheel, but the bolt is where most of the stretching happens.

Ideally, you would want the bolt to be stretched to the point where it is creating the most tension possible while not exceeding the bolt's limit.

Too tight, and a sudden impact such as hitting a bump at high speed could push the bolt over its elastic limit, and it will break.

Not tight enough, and the wheel and nut can move too easily, and slowly loosen.

A torque wrench is an easy and inexpensive way to measure the amount of stretch on the bolt. Advertised torque ratings are calculated based on the materials used in manufacturing to give a good approximation of the ideal value.

In high performance applications, the tension is actually measured by measuring the stretch of the bolt, regardless of the torque required to achieve that stretch. But that requires more expensive instruments, and for everyday drivers it's usually overkill.