99 Jeep Cherokee Sport

I'm going to replace the front brake pads and rotors. To buy the replacement parts I need to know if the rotors are 78mm or 82mm. I assume the ones on the car now are the ones it came with originally. I've owned it since 2002, and I have not had them replaced. Is there any way to know which size are likely to be on the car? Why would some cars have 78 and some have 82? What's the difference? I'm trying to avoid jacking it up and removing a tire to measure a rotor. Thanks.

 

Important you get the right ones.
Mid year change is why there are two.
This is pretty detailed at Post # 2.

https://www.jeepforum.com/forum/f11/...e-hubs-360959/

If this were me I am taking one off and bringing it to the store. LOL.