The MotoGP Bridgestone Asymmetric Rear Tire
Please click on the above image to view it larger.
Meet the MotoGP Bridgestone Asymmetric Rear Tire after a hard day’s work.
This Medium compound example was used by Valencia race winner Marc Marquez. Since the Valencia circuit has nine left corners and five right corners, this asymmetric rear tire has harder rubber on the left shoulder and softer rubber on the right shoulder. The compound in the middle is designed to handle the stress generated by acceleration rather than high speed cornering.
As the tires heat up and soften, friction during cornering pushes small amounts of rubber to the edges of the tires. You can see this on the image above, where on the very edge of the tire there are bits of tire rubber balled up but still attached to the body of the tire. These bits are sometimes called ‘marbles’ or ‘slag.’
When the tire exits a corner and accelerates to a sufficient speed, the centrifugal force acting on the tires causes some bits of slag to separate from the tire body and fly into the air. For another close up of still-attached slag, click here.
They then lie around the track where they might be picked up by another hot, sticky tire. If a tire covered with slag never accelerates sufficiently to throw those bits away, the slag can remain attached all the way to parc fermé as shown in the top image.
When a MotoGP Bridgestone Asymmetric Rear Tire is new, the seams between compounds are not as obvious. Only as the wear generated by use causes them to deteriorate at different levels so the compound seams become easily identifiable.
This brand new tire shows seams of a different kind, perpendicular to tire rotation.
This slightly used tire shows wear caused by several laps. You can even still see one of the perpendicular seams in the lower left.
To compare with the race-distance tire and see to what degree it changes over the course of approximately 75 miles, click on the image at the top of this post for a close up. A Facebook comment also pointed out that Marquez’ tire suffered a celebratory burnout at the end of the race, which is what added the parallel grooves in the rubber.
For another comparison, here is a shot of the tire Rossi rode to second place. I don’t believe he did a burnout after the race:
You may also find Bridgestone’s online tire glossary interesting.