I put bias 7.50 on the rear that had a road diameter of 31 inches to help my gearing. They are Power King. They are a hwy tire, but they also offer a Power King with an aggressive tread that has a 33 inch diameter. Every couple inches will give you abooouuut 5 miles per hr. in the 50mph range. I think it is a good trade, expecially since now my granny gear is boardering on useful. Check the charts for more exact numbers tho. - Scott
