Originally Posted by shashankmittal
I could be wrong, but I think the reason for 17" rim is that 17" is pretty much an industry standard these days for dirt, sport and ADV bikes. There are more tire choices for 17" rims and tire availability is not so much of an issue (specially in scenarios when there aren't too many bike shops around).
Shashank: Why are you saying the 17" is a standard for dirt?
As far as I know, all 250 and 450 dirt bikes have 18/21 as stock and I don't think that trend is changing. 18" is also stock on KTM690 and I believe the KTM 990 Adventure as well.
I am interested in this question that was originally raised in this thread, Why didn't BMW go with a 18/21" combo for the F800GS... and how an 18" might change the F800GS dynamics. I have an 18" rear (Excel rim by Woody's) but I have not ridden either the 18" or the 17" enough to give a fair comparison as I have a new F800GS. I ride 70% off road / 30% on.