I used to own a 2000 F150 4X4 that had the 265/70-17's on it. I purchased a set of tire chains for the truck, but I no longer own it. I recently pruchased a 2001 Expy 4X4 with 265/70-16's and was wondering if the chains will still fit??

Are the tires the same diameter even though the rim sizes are different??

 

No, they are not the same diameter. A 265/70-17 is approximately a 32x10.50-17 while a 265/70-16 is approximately a 31x10.50-16. They are the same width, but different heights. A 265/75-16 would have been the same height and width as the 265/70-17's.