IMSA’s premier sportscar series makes its racing debut at the tight and twisty 1.654-mile, nine-turn temporary street circuit in downtown Detroit on Saturday, with its GTP and GTD Pro classes making up a 21-car field.
Tandy won pole from Porsche Penske Motorsport team-mate Dane Cameron by 0.124s in qualifying on Friday afternoon. Although his time was 3.7s quicker than the fastest GTD Pro car, the difference in the way the classes make their lap time will pose a unique challenge.
“What's so different here is going to be the interaction between the two classes,” Tandy told Autosport. “I think it’s something that's different here to anywhere else.
“We're basically quicker than the GTD cars in three areas, which are the three big straights. But pretty much all the braking zones, because of the ABS they have, and a lot of the sharp corners, because they're a lot shorter wheelbase, the GTDs are actually quicker than the GTPs.
“If we don't pass a car that we’re behind by Turn 3, we will not pass them until Turn 1 on the next lap if we're lucky.
“We won't get held up so much, although we lose time in dirty air, of course, but we cannot stay on their bumper because of the ABS and the short wheelbase that allows them to rotate the car faster.
“They are genuinely quicker in all the slow corners. So, the class interaction is going to be different for sure.”
Tandy says that Turns 1 and 3 are the only true passing places for the big and heavy cars, although the GTPs with their electrical hybrid boost system are topping 185mph on the long straight into Turn 3.
He says that means overtaking among the prototypes will be limited: “In class, there is no passing zone, there has to be a mistake made – because even in the draft down the back down to Turn 3, you've got to be on the gearbox out of Turn 2, which is almost impossible to do.
“Because this circuit has so many slow speed exits all the time, so you have the whole accordion effect where the car in front will always get on the gas at one car length before the previous one.
“If you are close with a class rival into braking for Turn 3, anything could happen. We brake at over 500 feet, so it's quite a big braking zone.
“But, in sportscar stuff, there's lots of opportunity that comes up with multi-class racing, so you've got to be ready to take your opportunity.
“As for dealing with GTD traffic, it's even tougher for us to get a run out of the last corner and pass into Turn 1, they've got to be willing to let us go.
"It's totally different to even Long Beach [IMSA’s other street sprint event], for example.”
