Tires

OEM Tires
The OEM tires are sized 245/60-18 on the 2000-2001, and 245/70-16 in 1999.

Aftermarket Tires
285-55-18 is said to be the largest tire you can mount on the stock 18" rims without lifting or trimming. 285-60-18 will take minimal trimming of the cladding.

Insane
Using an 8 inch lift, one owner has managed to install "40x16-R16 super swamper LTB's". The forum consensus appears to be that this is unworkable. Photo