pretty sure they're 8.5" wide...looking at those 12.5" tires on Scott's, i'd say that seems about right.
I read somewhere that the new 2500 wheels were 9", but I could be wrong. I will see if i can find that. My 1500 wheels were definitely 8.5"
I have 20K miles on these, and I am not getting any abnormal center wearing on them. I was worried. I do like the look of the wider tires on the narrower wheels

