Originally Posted by NKL
Why? A 150 rear tyre is plenty for 100hp.
Its a matter of tyre geometry (and lack of tyres than can handle power) rather than width.
150/70 is not that good of a street tyre profile.
Perfect street rim size for our bikes is 5"
Having said that, the stock scorpion on the stock 4.25 rim is just huge, larger than the 150 indicated. It is as wide (if not wider) than an 150/70 anakee2 on a 5" rim.