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Practice, Performance and Preparation Paramount for GTP, GTD PRO Competitors in Detroit
May 29, 2025
By David Phillips
IMSA Wire Service
DAYTONA BEACH, Fla. – The IMSA WeatherTech SportsCar Championship schedule is nothing if not diverse. The second weekend in May found competitors tackling California’s flowing and bucolic WeatherTech Raceway Laguna Seca road course. Now the final weekend in the merry month of May finds competitors in Michigan taking to the confined, urban streets of the Chevrolet Detroit Sports Car Classic.
If NASCAR and IndyCar have their oval “bull rings” in Martinsville Speedway and Iowa Speedway, respectively, then IMSA’s version of a street course bull ring is the 1.654-mile, nine-turn Motown circuit where paint is often traded during overtakes and the omni-present concrete walls await the slightest mistake from the field of 22 cars, split 11 apiece between Grand Touring Prototypes (GTP) and Grand Touring Daytona Pro (GTD PRO).
A “Street Course” BoP: Balance of Practice
Given the track’s tight confines and a schedule that shoehorns a couple of practice sessions and qualifying into a single day on Friday, competitors must walk a fine line. If Job No. 1 is to extract the ultimate performance from drivers and machines, Job No. 1a is to keep those machines intact throughout practice and qualifying.
Any incident in Detroit could create a snowball effect for drivers and mechanics in terms of repairs and tip-top car prep for Saturday’s 100-minute race. Additionally, any significant loss of track time will limit the ability of drivers and their race engineers to determine their car’s optimum mechanical and aerodynamic set-ups, let alone gather data on the performance and wear of their Michelin tires.
“It’s a short weekend, so Friday is really busy with two free practices and qualifying,” says Klaus Bachler who, together with defending GTD PRO champion Laurin Heinrich, will co-drive AO Racing’s No. 77 Porsche 911 GT3 R. “You need to bring it at some point, because there’s no room for any mistakes. Otherwise the weekend can be over quite early. It will be difficult because I think qualifying and starting position is very important. It’s half of the race, maybe.”
Drivers need to be extra careful to avoid triggering a red flag in practice, given the ramifications that causing a red flag automatically forfeits a car’s fastest qualifying lap per IMSA’s rule book.
“There’s probably only two places that are good to pass or possible to pass without a big amount of risk,” says Nick Yelloly, who will co-drive the No. 93 Acura Meyer Shank Racing with Curb Agajanian’s Acura ARX-06 GTP car with Renger van der Zande. “There’s probably another two that I would try and have done on opening laps, but they’re very high risk . . . So clearly our aim is start on pole and drive away into the distance. That makes our life a lot easier on the street circuit. But IMSA racing and how everything is going, you never know what’s going on and what it’s going to throw you that weekend.”
Of course, there’s always the chance a team can steal a march on the competition by gambling on tire, fuel and/or pit stop strategy, especially in the event of a full-course caution. As well, crews can also gain track position with sterling pit stop execution. Detroit’s split pit lane has GTP cars on one side, GTD PRO cars on the other. The fact remains that chances of standing on the podium on Saturday are greatly enhanced by fast – and clean – performances throughout practice and qualifying.
The “Traditional” BoP: Balance of Performance
The GTP and GTD PRO pecking orders may get shaken up this weekend, following IMSA’s detailed look at various cars’ performance in the early rounds of the season after a detailed, data-driven process by the IMSA Technical Committee.
Weight has been added and power taken away from the Porsche 963 and the BMW M Hybrid V8 GTP cars. Conversely, minimum weight has been reduced and power added to their Acura ARX-06 and Cadillac V-Series.R competitors. As for GTD PRO, minimum weights on seven of the nine manufacturers were modified along with power adjustments to all cars.
The adjustments come ahead of the fifth race weekend of the WeatherTech Championship season, slightly ahead of IMSA’s typical five-race “rolling average,” following a deeper dive post-Monterey and the continuation of noteworthy streaks across multiple classes.
“All of these changes are based on a data-driven process,” IMSA President John Doonan explained in a wide-ranging conversation last week, while also highlighting many of IMSA’s first quarter achievements in 2025. “We’ve realized that the rolling process hasn’t reacted fast enough in equal and fair competition.
“You want to do the right thing and make adjustments that are based on a process, but also when things are somewhat diverging in terms of competition, when you have got a couple of cars outside the performance base band and a couple of cars below it on the low side, you want to bring everybody together. And I think anybody that wants to see exciting competition would want what we’re trying to do here in both GTP and GTD PRO as we head to Detroit.”
A “Travel” BoP: Balance of Preparation
Drivers, start your air miles. While Detroit runs before the WeatherTech Championship’s brief pre-summer break, many IMSA regulars will contest the 24 Hours of Le Mans, June 14-15, while all four WeatherTech Championship classes are back in action at the Sahlen’s Six Hours of The Glen from June 19-22.
For Cadillac in particular, going from “home soil” in Detroit against the backdrop of the Renaissance Center then across the ocean to Le Mans, the next month is going to be hectic. Some team members will spend 27 days away from home between IMSA rounds at Detroit and Watkins Glen, and travel more than 8,700 air miles.
Both its IMSA GTP teams – Cadillac Whelen Racing (prepared by Action Express Racing) and Cadillac Wayne Taylor Racing – will head from Detroit to Le Mans, albeit with different chassis.
All four of their full-season IMSA drivers will race at Le Mans, but Whelen’s Earl Bamber shifts to his full-season FIA WEC entry for Le Mans with Cadillac Hertz Team Jota and WTR’s Louis Deletraz will be in an AO by TF Le Mans Prototype 2 (LMP2) class entry. The Taylor family’s effort sees Jordan and Ricky Taylor racing together with Filipe Albuquerque at Le Mans.
Indeed, virtually the entire cast of IMSA GTP regulars will be in action at Le Mans, with 18 of the 22 full-season GTP drivers competing at Detroit also competing at Le Mans. It’s easier to note the four that aren’t. BMW M Team RLL’s Marco Wittmann and Philipp Eng and JDC-Miller MotorSports’ Gianmaria Bruni and Tijmen van der Helm are the quartet that aren’t adding another French stamp to their passports in the next two weeks. We’ll have more on where the rest of the GTP field is at for Le Mans in the coming days.
But first, there’s a 100-minute Detroit battle to watch. Be sure to follow all the action from the Chevrolet Detroit Sports Car Classic this weekend on Peacock, the IMSA Official YouTube channel and, internationally, on IMSA.TV as well as IMSA Radio (XM 206, Web/App 966).
