Heading into the shortest race of the 2014 TUDOR United SportsCar Championship, just 100 minutes on the 1.968 mile street circuit at Long Beach, April 12, the question for Michelin teams is will they or won’t they change tires? If yes, then when—and why?
Extended tread life is long a hallmark of Michelin performance. “History has proven that the Long Beach race can be won on a single set of Michelin tires,” said Ken Payne, technical director motorsports, Michelin North America.
Payne notes that Michelin engineers have increased the number of stints or fuel loads without tire changes or performance drop offs to as many as five stints for Prototypes and three stints for production based GT cars at the fabled 24 Hours of Le Mans.
Although teams must start the race on their qualifying tires, some Michelin technical partner teams in both Prototype and GT competition have won previous Long Beach races by not changing tires on their pit stops.
So why change tires at Long Beach 2014? The answers are short race, data and new rules.
Capturing more data than virtually any other sport, Michelin technical partner teams track and transmit scores of sensor channels thousands of times per second with real time telemetry transmitted back to the pits. The data overload would make the most diehard sabermetricians swoon.
Each team has at least one DAG (data acquisition geek) per car whose sole responsibility is to gather data. They monitor and analyze engine and chassis performance, including steering, braking and throttle inputs, engine intake, exhaust, brake and tire temperatures, car track position, shock absorber travel and car ride height and dozens of other factors.
In preparation for Long Beach, teams study past races and videos, analyze the data and run detailed race strategy simulations.
Each car must pit at least once for a required driver change. At some stage, the car needs to be refueled.
“The simplest scenario is to make one full service stop,” said Payne. “I can also envision a scenario where, given the timing of caution periods, a team stops twice for splashes of fuel and never changes tires,” said Payne. Under prior rules, changing tires added approximately 12-15 seconds to the pit stop as tire changes could not take place while the car was being refueled.
But the new series brings new pit rules for 2014, permitting tire changes and refueling to be conducted simultaneously. “Any pit time advantage gained by staying with the warm tires is neutralized. With no time lost on a tire change, teams are now more likely to go for fresh tires, if they only stop once,” said Payne.
That raises the question of when. Like accountants taking inventory, some teams use a FIFO (first in/first out) strategy, ready to be the first to pit as soon as they reach their fuel window, approximately 40 minutes into the race. By pitting early they hope to avoid pit traffic, exit into an open area of track and gain track positions as others pit or a full course caution is initiated.
On track issues can quickly trash a team’s primary strategy, making experience and the ability to change on the fly essential. BMW Team RLL won the 2013 Long Beach GT race despite an early incident forcing them into an early pit stop and tire change. The team changed drivers, added fuel, took on new tires and later pitted for just a splash of fuel while the competition did full service stops.
With GT race laps in the 78-82 second range, teams have approximately 30 seconds after the car passes the start/ finish line to make the call to pit or stay out.
With factory prepped cars and top drivers evenly matched and little time to recover from any miscues, the pressure is on the teams, engineers, strategists, DAGs and tire engineers to make the winning call.