Michelin IMSA Insider: The Cycle of Track Surface Life

Here is today’s question: What do Steve Jobs, Prince, and Elon Musk have in common with Laguna Seca Raceway?

The answer is 2007. That is the year that Jobs introduced the first iPhone, Prince performed at half time of Super Bowl XLI and Musk showcased the first Tesla model at auto shows. It is same year that Laguna Seca Raceway was last repaved.

There are no fixed timetables for a track surface’s life. Surfaces wear at different rates depending on location, initial construction, composition of materials, weather, and use. As a racing surface ages, track temperatures and tire wear rates can also change. 

A repaving scheduled for 2020 was delayed by COVID-19. Given the popularity of the Monterey venue for races, schools, product launches, and events and the requirements for scheduling, and rescheduling postponed events, the revised date is not yet final.  

The Surface Cycle

Once a track is repaved it will begin a new cycle.

For example, following the late Spring 2007 paving in Monterey, the combination of fresh, dark asphalt and hot, sunny July weather produced track temperatures north of 140 degrees.

After a track surface has had a few years of weather and use, the surface gradually becomes a bit grayer, reflecting more sunlight rather than absorbing it. Track temperatures begin to normalize and the extra grippy microscopic rough edges of the fresh surface wear away and the track becomes less abrasive.

In later stages, the top surface layer or binder, which is approximately 4 cm. or 1.57 inches deep, starts wearing through, gradually exposing the coarser aggregate underlayer.

Working Through the Range

Robbie Holley, the Michelin series manager for Pilot Challenge, recalls double stinting the then new Michelin “street soft” tires to victory at Laguna Seca with the Muscle Milk team nearly a decade ago. 

That could not happen today due to the increasingly abrasive track surface. 

Michelin recently claimed its 24th consecutive overall race victory at Le Mans, where the tire company’s media materials noted that, “soft tire compounds are ideally suited for non-abrasive tracks and nighttime running.

“Medium compounds are designed for somewhat higher temperatures and more abrasive surfaces, and the harder tire compounds are used for higher temperatures and more abrasive track surfaces.”

The Family Connection

“Temperatures are an important factor in determining tire selections, but the level of track surface abrasion both at macro and micro levels is an equally important factor,” said Hans Emmel, Michelin WeatherTech Series manager.

So, as the track surface in Monterey has gone through its life cycle, Michelin has gradually migrated its tire selections through its range, from its softer compounds to mediums, and now this week, IMSA teams will race on the harder range Michelin tires.

The Michelin IMSA tire constructions are from the same family of tire constructions; the difference is simply in the tread compounds. 

However, one thing has not changed.  “This is a great track, and we should have some great racing,” said Emmel.