the general rule is to run one type of tire on the car, that running one type up front & another type out back will cause "unpredictable handling characteristics", and i was forced to tell this to customers. but i truly believe it's absolute bullsh**, and neither i nor anyone i've ever known has ever had a problem of any kind running mixed types, street or track. it was about selling tires. you sold the sportsman pros, so now you MUST tell the customer his front tires are no longer compatible. $$$chi-ching$$$! :|