IMSA Wants a GTD Pro Car From Every GT3 Brand. The Class Is Losing Teams Faster Than It Can Add Them.

Filed under: Endurance · Analysis

Inside five days at the start of August, IMSA lost two GTD Pro operations and floated a rule that would require more of them. The sequence matters more than either item on its own.

On July 31, Sportscar365’s John Dagys reported that Paul Miller Racing’s staff had been told the previous day the team would not continue in 2027, at least in its current guise. The team was leading the GTD Pro standings at the time, with BMW factory drivers Connor De Phillippi and Neil Verhagen opening the year with a class win in the Rolex 24 at Daytona — its first in GTD Pro. On August 3, Pfaff Motorsports confirmed it will pause its WeatherTech Championship program at season’s end, a decision communicated to crew members during the Road America weekend. On August 4, IMSA president John Doonan told Sportscar365 that the sanctioning body is evaluating a requirement for every GTD manufacturer also to field a car in GTD Pro, potentially starting next season.

The data argument is the strong part

Doonan was explicit that the motivation is Balance of Performance, not show. All-pro lineups produce a cleaner performance signal than Bronze- and Silver-rated stints, which carry driver variance that no amount of post-processing fully removes.

“I think it’s another key element of gathering every element of a data book that can help us with BoP,” Doonan said. “When we base a particular platform’s performance, best car, worst car, whatever. You take the MRC, the most representative car, to use as the benchmark for the [next race].”

That is a real technical problem, and the proposed fix would genuinely help solve it. Ten GT3 manufacturers are active in the series; Aston Martin, Ferrari and Mercedes-AMG lack full-season GTD Pro entries, meaning IMSA currently reads those three platforms mostly through Pro-Am data or one-off Michelin Endurance Cup and Daytona appearances.

The bill lands on the wrong desk

Strip out YRB Racing, which has signaled a full-time Aston Martin Vantage GT3 Evo GTD Pro program for 2027, and the mandate effectively applies to two brands: Ferrari and Mercedes-AMG. Both run GT3 as customer racing rather than a works operation. Doonan acknowledged the split himself — manufacturers with factory or works-supported GTD Pro programs are largely indifferent to the idea. At the same time, those selling cars to customers have raised internal concerns, because they do not dictate where those customers race.

That is the whole objection in one sentence. A works program absorbs a mandated entry as a budget line. A customer program cannot conjure a customer. Faced with a rule, the brand either funds the car itself — a factory entry under another name — or reconsiders whether GTD is worth the exposure at all. Neither outcome is what IMSA is aiming for.

And the entry base is not in a position to absorb a new obligation. Beyond Paul Miller and Pfaff, Sportscar365 understands a third GTD Pro operation will also be absent next year, amid what it described as rising costs and “other factors which competitors are no longer able to discuss in the media.” That clause is the most revealing line published about GTD Pro all summer. Lamborghini appears likely to remain in the class through a tender that has drawn bids from Riley Motorsports and Wayne Taylor Racing, with WTR believed to be the leading candidate — but a manufacturer changing partners is not the same as a class holding its car count.

Chris Pfaff, for his part, was clear that performance had nothing to do with his decision. “Despite the struggles, Lamborghini has been fantastic to work with,” he said, pointing to his December 2025 purchase of Canadian Tire Motorsport Park and a shift toward developing Canadian drivers. Paul Miller team principal Mitchell Simmons offered the same absence of a competitive explanation: “We’re not sure yet. We don’t have any contracts yet.” The desire to stay, he said, is “absolutely, 100 percent” there. Teams are not leaving because they cannot win. They are leaving because the arithmetic stopped working.

There is a better instrument already booked

IMSA does not need a season-long mandate to get all-pro data, because it has already scheduled something cleaner. The first joint IMSA/SRO Balance of Performance test runs December 12-13 at Daytona, with cars in IMSA specification—torque sensors, Michelin rubber—and one entry per GT3 manufacturer, modeled on SRO’s long-running Paul Ricard format. Doonan’s description of it is worth quoting in full for what it implies: contracted drivers unaffiliated with any OEM driving all the cars, “a very strict format of tire sets, when we use new tires, old tires, one-stint old tires, chassis settings, camber, caster, ride height, wing settings, full range of traction control, all the different engine maps.”

That is a controlled experiment. A race is not. Road America made the point on August 2, when Pfaff’s Andrea Caldarelli and Sandy Mitchell won GTD Pro from eighth on the class grid — the Temerario GT3’s first endurance victory — on the strength of caution timing and pit-wall calls rather than raw pace. “I think it was a bit of luck but at the same time it was a massive strategy job by the guys,” Caldarelli said. Whatever the BoP department learned from those six hours about the relative performance of a Lamborghini and a Porsche 911 GT3 R Evo, it learned it through several layers of noise.

So the honest comparison is this: a mandated extra GTD Pro entry adds a season of contaminated race data at real commercial cost to the manufacturers least able to justify it. In contrast, the Daytona test adds a clean data set in two days at a cost the OEMs have already agreed to bear.

Run the test first

Acura’s confirmed pause leaves GTP with four factory efforts in 2027 — Aston Martin, BMW, Cadillac and Porsche — and Genesis has pushed its IMSA debut to 2028 at the earliest, with Cyril Abiteboul citing the Acura news and “the dynamic of the championship” as reasons to wait. Against that backdrop, the risk of a GTD Pro mandate is not that it fails to improve BoP. It is that it improves BoP for a smaller grid because of it.

Doonan said a decision is needed “real soon,” and that no bulletin has gone out. The right call is to let December happen first, measure how much of the data gap the Daytona test actually closes, and only then decide whether the remainder is worth charging Ferrari and Mercedes-AMG for.