I have read in the Owner's Manual that a range is provided for the wheel lug nut torque spec: 80-108 ft-lbs.

This is the first time I have encountered a range rather than a specific value. Is there an optimal specific torque value I should use? I would think the lower end of the range would make it easier to change a flat tire.

Thanks in advance for any help.

 

Those specs are correct and should be done in the following sequence (after initial tightening with a wheel/lug wrench).
You can choose the low or high end.
I doubt many people actually carry a torque wrench for the possibility of changing a flat.
Meaning torque specs are a moot point out on the road for the average driver.

 

Checking with my fairly new and hopefully calibrated Olsa torque wrench, the factory nuts on three wheels were at 94-96 ft-lbs.

I installed locking lug nuts and then torqued everything to 90 ft-lbs. If a tire has to be changed roadside, 90 will be easier to loosen than 108.

 

The reading removing a lug nut is never as accurate as most think when determining what they were torqued at unless you tested right after they were installed and torqued? But why would you do that? lol.
I would have recommended 100lbs in 25lb increments.
You should also check the torque after driving around your neighborhood. You may be surprised to find a couple not at the set torque.

 

I didn't test torque by loosening lug nuts. I don't know how to do that. I wouldn't use a torque wrench to loosen anything.

I set my torque wrench to 80 ft-lbs and attempted to tighten a lug nut. Wrench clicked (broke over) immediately with no turning or movement of the lug nut. So the factory torque value is more than 80 ft-lbs. Then the wrench was set to 85 ft-lbs and another try; again, the wrench clicked with no turning of the nut. Then the wrench was set to 90 and 92 and 94 with the same result. At 96 ft-lbs, the nut turned before the wrench clicked. I conclude the factory torque was about 95 ft-lbs. Is this method reasonable?

 

Not sure why you would do that. It has no real conclusion if you drove several hundred miles after the last time the wheels were torqued without checking them.
But we could talk about the physics of proper torquing all day. Sounds like you made your choice on a torquing value you want and that's that!

We always have the customer sign the paper to recheck the wheel torque after 50 miles and that we will check it for free. In my shop your wheels would have been torqued to 100lbs.

 

This car is a few days old and has less than 60 miles on it.

I performed this test because I wanted to see what torque the factory used. That was useful information because the owner's manual states a wide range: 80 to 108 and I wanted a better idea for a specific torque value.

Regardless of what your shop does, the factory torque on my sample was about 94-96 on lug nuts on three wheels.

I do agree that the torque should be checked after some miles.

 

I set all wheel nuts to 130nm or 96ft-lb in the old language.

 

There are several engineering problems with this method of overthinking his torque audit. What the OP is measuring is residual torque, which the typical home torque wrench is not very good at. He is first measuring the energy required to overcome the friction between the threads, which may not be the same as the original tightening torque - in fact it is most likely not. While he may feel that he is reverse engineering the fastening value, the OP is fooling himself if he thinks he knows the actual torque used by the factory. His best course of action is to use a torque value within the recommended range - which is surprisingly wide. The source below uses the middle of that range, and is the value I personally use.

https://www.sparkyexpress.ca/blogs/a...t-torque-specs

 

Exactly ^^^^^^^^^^^^^^^^ but in the DIY world .... they are all experts. LOL