Following the release of the Balance of Performance adjustments for the Prototype and Prototype Challenge classes, IMSA has issued pre-Rolex 24 changes for a number of production-based cars in GT Le Mans and GT Daytona as well.

The ACO-spec GTLM class sees notable changes for three of the six manufacturers, including Porsche’s new 911 RSR, which has received a 15 kg weight increase, but a slightly larger (0.3 mm) air restrictor, which will give the factory-run entries a marginal boost in power.

Both the SRT Viper GTS-R and Ferrari 458 Italia have been given weight breaks, with the Riley-built machines shedding 30 kg and the Prancing Horses from Risi Competizione and Krohn Racing allowed to lose 15 kg from the specification it ran at the Roar Before the Rolex 24.

Additionally, the Viper will be allowed to carry up to 120 liters of fuel, a 10-liter increase over other cars also running IMSA’s E85 fuel.

In GTD, numerous changes have been made to nearly every marque.

Porsche’s 911 GT America sees a 35 kg weight increase, with the Ferrari 458 Italia GT3 allowed to shed 29 kg but run with a hefty 5 mm smaller air restrictor. The Prancing Horses, however have been given a 200 rpm boost to help compensate.

Both the Aston Martin Vantage V12 and SRT Viper GT3-R have received larger air restrictors, with the new-for-2014 Viper also getting a boost in fuel capacity but at a 300 rpm reduction.

The BMW Z4 GT3, Aston Martin and Viper will be allowed to use a slightly different front Continental tire, while the Z4 and GT3-R additionally both will have a 15 mm reduction in Gurney size.

Audi’s R8 LMS, which led the way at the Roar, has received a 200 rpm boost, with changes also having been made to the rear wing height for the Porsches, Ferraris and BMW.

Fuel capacity across the board has been reduced from 90 to 86 liters, with the exception of the Aston Martin and Viper, which are allowed to run at 90 and 95 liters, respectively. Additionally, the Porsche now has a maximum capacity of 85 liters.

The adjustments take effect only for the TUDOR United SportsCar Championship season-opening Rolex 24 at Daytona, with more changes likely before the second round of the season at Sebring.

GTLM & GTD BoP Changes: Click Here

