On my last set of AV71/72 Cobras I got 20,000km the rear was totally gone but the front still had 3-4K to go. Have now changed out to the new chromes and wow what a difference, streets ahead in grip, corner speed and improved ability to change direction. I am sure its the rear/front crest radius combination and compound that has improved the bikes handling capability, the best investment I have made and has transformed my R3.