How many days do you get out of a set of R4?This is one reason why I use Porterfield R4 (track specific) and Porterfield R4S (street/autox/light track) as the compound is interchangeable. The R4 take over track duty up front and the R4S are adequate in back on the track. For street and autox the R4S are on front and back. I’ve even run the R4S on all corners at Sebring but with limiting them to 20 minutes per session. With the R4 up front I can stay out as long as I want and brake as late and hard as I wish.