IMSA WeatherTech 2026

John and Peggy Bishop founded the International Motor Sports Association in 1969 with money from Bill France, the NASCAR boss, who took three quarters of the stock. Twelve years later Bishop made the decision that defined the place: the FIA had just introduced Group C and he refused to copy it. He invented a class of his own, GTP, and that stubbornness produced North America's golden age of the prototype — Porsche 962s and turbocharged Nissans — until the category died in 1993. The name came back in 2023.

The two races that hold the calendar up are older than IMSA itself. Sebring has run its 12 Hours since 15 March 1952, on the concrete slabs of a Second World War airfield. Daytona went to twenty-four hours in 1966, and Ken Miles and Lloyd Ruby won the first one in a Ford Mk II.

Today's championship was born of a truce. In September 2012 came the announcement that the American Le Mans Series would merge with Grand-Am's Rolex Sports Car Series, two rival championships that had spent more than a decade cutting American endurance racing in half. They ran as one from 2014, and since 2016 the series has been the IMSA SportsCar Championship.

Four straight wins to open the year had 2025 settled before spring. Porsche Penske ended up winning all six titles GTP hands out: drivers, teams and manufacturers, plus the same three in the Michelin Endurance Cup. Matt Campbell and Mathieu Jaminet took the drivers' crown in the No. 6 963, sealed with third place at Petit Le Mans; Felipe Nasr and Nick Tandy took the endurance title in the No. 7. It was the team's second year in a row, after winning in 2024 with that same No. 7 car.

That season also brought a noise the class had not heard in thirty years. In March, at Sebring, the Aston Martin Valkyrie raced in IMSA for the first time with its naturally aspirated V12 — the only twelve-cylinder on the grid.

And the year's closing image was not Porsche's. At Road Atlanta, while the No. 6 nursed home the third place that won the title, Whelen's No. 31 Cadillac won Petit Le Mans with Jack Aitken, Earl Bamber and Frederik Vesti driving. That car and those three names come back to Daytona in January untouched.

Porsche Penske defends all six titles at once, a position as comfortable as it is awkward: anything short of repeating will read as a step back. It keeps both 963s: the No. 6 of Matt Campbell, last year's champion, alongside Kévin Estre and Laurens Vanthoor, and the No. 7 of Felipe Nasr.

Facing them are eleven GTP cars and five manufacturers. Cadillac attacks on two fronts, with Whelen's No. 31 — Jack Aitken, Earl Bamber and Frederik Vesti, the crew that won Petit Le Mans to close last year — and both Wayne Taylor entries. BMW fields two M Hybrid V8s with WRT, Acura two more with Meyer Shank, and JDC-Miller runs a customer Porsche, which in endurance racing is no small detail: with performance levelled out, a well-drilled private team beats the factory that sold it the car.

And there is the No. 23 Aston Martin, going into its second year with a car that resembles nothing else on the grid. Its debut season was an education; the question now is whether that V12 lasts until Sunday.

Eleven rounds between January and October, but GTP contests only nine: it does not run the Chevrolet Grand Prix at Mosport in July, nor the Michelin GT Challenge at VIR in August. Those two dates belong to LMP2 and the GT classes, so there are two weekends when the championship carries on without the big prototypes leaving the truck.

Five of the rounds make up the Michelin Endurance Cup and award a championship of their own: the Daytona 24 Hours, the Sebring 12, the Glen 6, the Road America 6 and the ten hours of Petit Le Mans. Road America joins that group this year, and does so at a new distance: six hours have never been run there before. It measures 6.515 kilometres over fourteen corners, and the championship has visited it thirteen years running.

Daytona is its own thing. It is the race that draws the people who do not compete here the rest of the year, and January's entry list says so on its own: Álex Palou in the No. 93 Acura, Scott Dixon and A. J. Allmendinger in the No. 60, Colton Herta in the No. 40 Cadillac, and NASCAR's Connor Zilisch making his class debut in the No. 31. Twenty-five prototypes on the same grid.

A GTP car is not an auteur's work. Almost all of them are LMDh: a chassis bought from one of four approved constructors — Dallara, Ligier, Multimatic or Oreca — plus a Bosch electric motor, an Xtrac gearbox and a Williams battery, identical for everyone who signs up. The manufacturer brings the combustion engine, the bodywork and the software, and the whole package is capped at 500 kW.

The exception carries number 23. The Aston Martin Valkyrie is built to LMH rules rather than LMDh: a naturally aspirated 6.5-litre V12 by Cosworth revving to 11,000rpm and no hybrid system at all. It is the only car in the class without a traction battery.

On top of all that sits Balance of Performance: the organisers adjust each model's weight and power race by race so nobody runs away. It is what lets a naturally aspirated V12 and a turbocharged hybrid fight for the same win — and why half the paddock complains every other weekend.

And one detail changes how all of this reads: these are the same cars that race at Le Mans. Daytona, Sebring and Le Mans are a single conversation again for the first time since the 1990s.