Michelin GTLM Insider: The Lime Rock Splits

What do ice cream parlors, bowling alleys, and Michelin GT Le Mans teams at Lime Rock have in common?

The answer is that all have their respective “splits”, be they banana, the 7-10, or GTLM team Michelin tire options at Lime Rock Park, the shortest circuit and the shortest lap time in the IMSA WeatherTech SportsCar Championship season.

“Although we haven’t raced at Lime Rock since 2013, in previous years our teams have often tried various ‘split’ tire fitments there,” said Ken Payne, technical director motorsports, Michelin North America.

The seven-turn, 1.474 mile circuit, with a chicane at the end of the backstretch, is unique in that all but one turn are right handers, leaving a single left hand turn.

Why Teams Choose to Split

“From a tire standpoint, most circuits place loads on both sides of the car, but here the right front tire is only loaded up on that one left-hand turn,” said Payne.

“Our Michelin GTLM technical partner teams are permitted to mix and match tire compounds and we have three options for them to work with.

“We expect that some of our GTLM teams will experiment with right side tires that are one temperature range cooler than the left side tires or choose a cooler temperature right front tire.”

New Territory for FCGR

For team manager Mike O’Gara and the Ford Chip Ganassi Racing team, Lime Rock Park presents yet another new opportunity in a debut Ford GT season that has already produced surprising success.

Having that many tire options available and the ability to mix and match sets is totally new territory for the CGR team, which for all its success in motorsports, has never previously raced in a category offering open tire competition.

“Imagine if you only have vanilla ice cream with one mandated tire compound, or even two mandated options like chocolate or vanilla required to be used in a race, but not permitted to be mixed,” said Payne.

“They then enter the Michelin world where we have three options, and you can mix or match them on different wheel positions.”

Theoretically, Michelin teams can try up to 39 different dry tire/wheel position combinations.

Having that many possible options was initially a bit overwhelming to the CGR team, but as evidenced by its current win streak and race winning double-stint tire strategy call at Canadian Tire Motorsport Park, O’Gara and the team’s drivers and engineers have quickly realized the Michelin benefits, which include a Michelin tire engineer embedded with each GTLM team.

Time to Split

On a short, quick track filled with 32 entries in three classes (PC, GTLM and GTD), traffic is constant and track position is a key to success.

“Qualifying at Lime Rock is very important for track position,” said Ford’s Richard Westbrook, who with co-driver Ryan Briscoe enters on a string of three consecutive WeatherTech Championship GTLM class wins.

WeatherTech Championship teams are required to start the race on their qualifying tires, but are permitted to change one tire.

That opens the door for GTLM teams to go with a cooler range tire for qualifying, but move to a higher temperature replacement on one wheel position for the start of the race.

“Teams can be tempted to go with cooler temperature range tires for qualifying to gain a bit more grip and improve their track position, but on a long green flag run, they may give that time back if tire temperatures get too high,” said Payne.

Lime Rock Park is not the only circuit where Michelin technical partner teams consider split fitments.

“Our teams frequently split fitments at Road America, some actually use all three options at one time there,” said Payne.

Fast and Consistent

“Lime Rock is very tough,” said recent Canadian Tire Motorsport Park GTLM class pole-sitter Antonio Garcia. “You are in traffic the entire time. The race is 100 percent traffic.”

“The short lap time (approximately 51 seconds) puts pressure on everyone. There is no rest for the driver or crew. It is very easy to go a lap down here.

“You need to have the right strategy. You have a big range of when to pit. Everything needs to work really well. You need to be consistent and tires are very important.”

“A full green flag stint at Lime Rock Park can be 65-70 laps compared to 14 or 15 laps at Le Mans,” said Payne.

“One of the keys to splitting tire fitments is to have the car well balanced, and the wear rates have to be in relative harmony.

“All of our GTLM tire options are currently developed from a common construction family with the difference being in the tread compounds.”

Maintaining consistency over the entire stint is essential for drivers working through traffic.

“The drivers are going to be making passes off-line,” said Payne. “They are going to put the car into spaces that aren’t ideal and they need the mechanical grip to help them be precise.

“The drivers have no time to rest and neither do the tires. At most tracks, the tires can cool a bit on the main straightaway, but here, the left side tires get loaded almost constantly and the main straight is not very long, so that cooling is minimal.”

Winning Strategy

“Strategy plays a big part at Lime Rock,” said Garcia, noting the lap range for pit stops is much wider than at most circuits.

“It is always interesting to see how each GTLM team approaches the race and how it plays out,” said Payne. “It never seems to unfold the same way twice.”

“The track, traffic, timing and length of any caution periods and track position all come into play and doing the split tire option gives them another range of tools to work with.

“The GTLM teams are so good and the guys making the strategy calls are so sharp that this is truly anyone’s race.”