Cycle World

Controlling Racing With Rubber That Melts Rather Than Chars

Using thermoplastic cross-linking to improve the show.

July 21, 2019

Anyone who has been to an old-time ecologically forbidden beach party lit by burning tires knows that tire tread rubber doesn’t melt. In fire, rubber chars.

In high school, we learned about the single-minded Charles Goodyear, who neglected his family’s well-being to continue his attempts to make rubber boots that didn’t turn to viscous slime in summer heat. He eventually succeeded, discovering what is now known as vulcanization. This is the cross-linking of latex’s long-chain polymer molecules by means of sulfur bonds. These cross-links, by joining myriad polymer molecules together, converted a gummy liquid into a useful elastic solid that was no longer capable of melting when very hot.

What I at least did not learn in high school is that there are methods of cross-linking polymer chains into rubbery solids that are capable of melting when very hot.

Now let's go back a few years to when it was decided that Michelin would be the next spec tire supplier for MotoGP. At that time, it was actually proposed by some that Michelin should be asked to intentionally make bad tires as a means of putting an end to the high corner speeds that some regard as a danger to MotoGP. So far as I know, Michelin did not and was opposed to such shenanigans.

In Germany, the top-10 MotoGP finishers were spread over more than 20 seconds. Implementing tires that lose their grip above a certain temperature would perhaps bunch up the riders, but safety considerations make it impossible to consider such a solution where motorcycles are concerned.Courtesy of Honda

Little did I know that such means already existed at that time, and that according to Formula 1 commentator Mark Hughes were being used in that series to “improve the show.” Tires made of such material operate satisfactorily up to a certain temperature, beyond which the cross-links that make the tire tread rubber solid begin to lose their grip. They melt. The result is that when an F1 driver uses skill to pull away from the pack—“Stop that man! He’s an elitist!”—tire temperature rises, some cross-links let go, grip falls, and that driver knows better next time. This bunches up the drivers and “makes a race of it.”

Clearly, because of the limited footprint of motorcycle tires and the obvious danger to riders, no one would ever apply such a technology to motorcycle sport.