Why do some vehicles use lug nuts and others use lug bolts. Is the Modern Spare kit fully compatible with both?

Regardless of whether your vehicle uses lug nuts or lug bolts, there are no differences in compatibility of the spare tire.

The reason a vehicle manufacturer chooses to use lug nuts or lug bolts is likely a matter of preference, as neither has a significant advantage over the other. 

Lug nuts secure a wheel to the hub by threading onto the studs that protrude out of the hub. 

Lug bolts secure the wheel to the hub using threaded holes in the hub. 

There are some Modern Spare kits that include a new set of lugs (bolts or nuts) because the factory lugs are somewhat unique and will not work with the spare. 

Please see the article here- Does my spare tire kit need new lugs?

Even if your vehicle requires the use of the new set of lugs we supply with your spare, you are not required to change or modify your vehicle in any way.