I am planning to install wheel locks and have the following questions:
If you feel wheel locks can provide better protection, go ahead install them. I installed OEM wheel locks when my 2016 CX-5 GT was new. I save the wheel lock key in the spare tire area so that I can have it readily available whenever I need it.
1. What torque do people usually use - Mazda has a range instead of a specific number. Does 90 sound reasonable?
In addition to inaccurate and inconsistent fluid change “approximate” capacities Mazda provided in the owner’s manual, such as you actually need 5.5 quarts instead specified 5.1 quarts for oil change on the 2.5T, giving a range on all torque specs instead of a specific value like everybody else is very strange and giving people an impression whether or not Mazda cares about precision.
Checked 2021 CX-9 owner’s manual and I was surprised to find CX-9, even the vehicle is much heavier and the tires are bigger, the torque on lug nuts is still listed as 80 ~ 108 ft·lbf which is the same as my CX-5!
To handle this torque range only by Mazda, I use the median value all the time sometimes have to use calculator to figure it out. 94 ft·lbf is the torque value I’d use on CX-9’s 18” or 20” wheels.
Noticed CX-9 also gets smaller in diameter compact spare, T155/90D17 101M, like the CX-5. T155/90D17 has 28” in diameter but CX-9 road tires, P255/60R18 107H or P255/50R20 104V, has 30”! Be aware of using it especially if you have an AWD!
At least the compact spare fits the front on CX-9, as the even smaller T145/90D16 106M compact spare provided with 2019 CX-5 2.5T can’t even fit the front!
2. Does anyone know what the manufacturer uses when torqueing at the factory - or, since there's a range, can one expect lack of uniformity?
Mazda factory uses robot to install tires. The torque should be consistent on all lug nuts with a single value. I believe they use the median value from the torque range.
3. Is it OK to torque only wheel locks without adjusting the other lug nuts to the same spec (since I don't know what the other lug nuts are torqued at; I assume then I will need to loosen all of them and re-tighten if I wanted to have the same torque on all of them; therefore, wanted to know if I could only do the wheel locks).
No, you really don’t want to use the torque wrench only to the wheel locks. You should check the torque to all lug nuts and wheel locks at the same time with a single torque wrench for consistency. Consistency is the key. For convenience, you can loose the existing lug nut and re-torque it one by one in criss-cross sequence to the desired torque value (94 ft·lbf) without jacking up the car. That’s what all dealers do when they check the torque on lug nuts during new vehicle preparation; and that’s what I’ve been doing after Discount Tire did any tire service to my vehicle as their torque applied sometimes is not that accurate and consistent with a beat-up torque wrench.