Inside The Blue Tent
One place every IMSA team is guaranteed to frequent on race weekend is Michelin's tire-preparation area.
One of the busiest places in an IMSA garage area is a large tent that’s often tucked away from where teams prepare their cars for race day.
It's unofficially known as the Michelin tire workshop, and it's a near-constant hive of activity.
Michelin became IMSA's designated tire partner in 2019, replacing Continental. Under the deal, it is the exclusive tire supplier for teams competing in the series' top classes. The agreement involves more than just sales, however. It also requires technical support all season, with the biggest commitment coming on race weekends.
IMSA teams are allowed to use a certain number of tires for each race, and it varies from event to event. The shorter the race, the fewer the sets of tires IMSA will allow.
At the recent WeatherTech Battle On The Bricks at Indianapolis Motor Speedway, a 2-hr, 40-min "sprint race," the top-class GTP and LMP2 teams each got six sets of tires for the entire weekend. But only three could be used for qualifying and the race. (Teams also have designated practice sessions and a pre-race warm-up.) The other classes got seven sets, with no usage restrictions.
Compare this to January's Rolex 24 race week, where GTP teams could use up to 26 sets in all--21 of them during the 24-hour race.
IMSA can change these allocations at its discretion, such as for weather conditions like excessive heat that affect tire wear. Wet-weather tires don't count against the allocation. If rain is in the forecast, IMSA will allocate additional, wet-weather tires.
Many teams simply purchase the maximum number of tires allowed. But teams can designate used tires that still have some track life as "carryovers" so long as their specifications match what IMSA has designated for the upcoming race. The only stipulations for carryovers--they must have been purchased directly from the tire manufacturer for an event "in the current season."
Why would teams opt for old tires instead of always buying their full allocation at each race? One word: money.
Michelin's 2023 tire prices for the WeatherTech classes start at $544. The most expensive tire, a 31-in. slick for LMP2 cars, is $795.
Put another way, if a car drops out of a race early, it may have $1,000 or more worth of decent rubber on it than can be used at a subsequent event.
Tires bought during race weekend are picked up at the Michelin tent. Anybody who has spent any time in an IMSA garage will recognize the flat-bed carts used to move tires around. Old tires and rims are carted to the tent and the tires are removed and replaced.
The first step for the tent technicians: determine what each team wants. Tires marked with an "X" will be scrapped, while ones labeled "S" will be saved and potentially carried over. A zero with a slash is a request for a Michelin inspection. (And yes, these marking guidelines are in IMSA's rulebook.)
While Michelin has a presence at each IMSA event, most of the technicians at the tent aren't Michelin employees. Rather, they work for Jackson Motorsports Group, Michelin's official race tire distributor and marketing partner. (Jackson also provides similar services for BFGoodrich in off-road racing.)
The tire workshop has three stations. The first is dismounting of old tires and mounting of new ones (unless the tire is marked "DMO" for dismount only).
Once mounted, the wheel and tire are sent to station two where they are filled with air and checked to ensure the seal is sold. (Teams later replace the air with nitrogen, which delivers more consistent tire pressures.)
Station three is the wheel balancer, where “static” balancing takes place. Similar to ones found at auto service shops, the machine rotates the tire and tells the technician if weight needs to be added, how much (in ounces), and exactly where to put it. The weight --adhesive tape--is added based on the machine's guidance.
Once teams have their allocated race-weekend tire sets, they must ensure these tires--and only these tires--are used on track. The Michelin tent technicians track tire sets for each team as a courtesy. But official tallies are kept using an automated RFID tracking system.
Introduced in 2018, IMSA's RFID system features chips in each tire embedded with both the assigned car's information and tire-specific data. RFID readers are positioned at pit road exit all weekend, tracking which tires are on which cars. IMSA's rules and the strict tracking mean tires assigned to one car cannot be used on any other car, even within multi-car teams.
While IMSA's tire-usage rules during official on-track activity are strict, they don't limit teams from being practical around the garage. For instance, cars may be seen with non-allocation tires marked with labels such as "ROLLERS" to signify they are for--what else?--rolling the car around the garage.
Rollers might be used on a trip to tech inspection, for instance, so IMSA officials can check a specific change a team has made. For final inspections, race-weekend allocation tires must be on the car.
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References
Michelin becomes IMSA tire partner in 2019
https://racer.com/2017/09/21/imsa-names-michelin-official-tire-beginning-in-2019/
Rolex 24 tire allocation
https://sportscar365.com/imsa/iwsc/diuguid-double-stinting-tires-to-result-in-different-approach
2023 Michelin tire pricing
https://www.imsa.com/wp-content/uploads/sites/32/2022/12/21/Michelin-Motorsport-Pricing-Action-IMSA-2023.pdf
IMSA rules and regulations
https://www.imsa.com/competitors/2023-imsa-rules-regulations/
Introduction of RFID
https://sportscar365.com/imsa/iwsc/michelin-implements-rfids-evaluating-future-usage/