The most successful team in the IMSA Continental Tire SportsCar Challenge history has suspended its program, with Rum Bum Racing announcing Monday that it will not continue its GS class campaign this year.

The Luis Bacardi-owned team, which debuted in 2010, has been one of the front-runners in the class with a total of 21 overall victories out of 66 starts, including back-to-back championships in 2012-2013 with Matt Plumb and Nick Longhi.

Most recently, Matt Plumb and brother Hugh have struggled with its aging Porsche 997, in a class that has seen an influx of new GT4-based and series-specific machinery.

The brothers’ Porsche suffered a mechanical failure in the season-opener at Daytona, although finished third last month at Sebring.

The team has not disclosed the reason for its withdrawal, although in a statement it said: it will “continue to evaluate competition possibilities in the future.”

Rum Bum’s withdrawal leaves only seven GS class entries, but 34 cars in total, for this weekend’s Continental Monterey Grand Prix at Mazda Raceway Laguna Seca.