The next two races on the IMSA WeatherTech SportCar Championship schedule, Lime Rock Park and Road America, are as different as lobster rolls and bratwurst, making them a good illustration of the Michelin approach to the GT Le Mans class.
Heading to the shortest (1.5 miles) and longest (4.0 miles) circuits of the IMSA season, the factory teams from BMW Team RLL, Corvette Racing, Ford Chip Ganassi Racing, and Porsche GT Team enjoy an uncommon luxury in North American motorsport, the ability to mix and match their tire compounds.
Michelin GTLM ‘Mix and Match’
While some forms of motorsport provide for more than one tire option at an event, teams are restricted to just one option at a time.
That is not the case in GTLM, the only IMSA class permitting open tire competition, where all of the factory teams and partial season entrant Risi Competizione Ferrari have chosen Michelin as their respective technical partner.
“Each of our GTLM manufacturers has pre-selected both the front and rear tire options, including their cool (soft), medium and warm (hard) temperature versions of our Michelin tires to use for the entire 2018 WeatherTech Championship,” said Ken Payne, technical director motorsport, Michelin North America.
“Once the GTLM teams have locked in their respective tire code selections with IMSA and Michelin they are then free to mix and match the tire compounds in order to optimize their car set ups and race strategies.
“Teams must stay within the IMSA tire allocations at each event, but If you tally up all of the various scenarios with three tire options and four wheel positions, there are 39 possible combinations,” said Payne.
Lime Rock and Road America Scenarios
“The advantage of being able to mix and match tires gives each team the opportunity to work toward an optimal set up and use the tire options to limit any compromises,” said Payne.
“Lime Rock is in some ways a distorted oval with six right turns and only one left hander, so rather than a square fitment (all four tires the same compound), the temptation is to run a softer tire on the right side or just the right front. The only time that the right front tire is really loaded is on the mid-speed left hander in the infield.
“Road America is also a clockwise circuit, but with much higher speeds and high load corners. Most of our GTLM teams prefer a harder tire on the left side, and some go with the medium options on the right side or maybe the medium on the right rear corner and the cool or soft tire on the right front.”
Making Mix-and-Match Work
The key to making a mixed and matched set-up work is maintaining balance on the car under braking and in having fairly even tire wear.
Looking to 2019
While the GTLM class will continue to be permitted to mix and match tire options in 2019, Payne confirms that IMSA and Michelin have agreed to designate only one Michelin option for the Prototype class and one for the GT Daytona classes in advance of each 2019 WeatherTech Championship event.