by its sponsor's moniker. This time, the series was more restricted to current models, that is to say models then currently available for retail sale in dealerships throughout the US. Other than that, the series had rules and race formats that were similar to the RS series, being an endurance series. At the end of the 1987 season, Champion stepped down as sponsor and was replaced by Firestone Tire and Rubber Company; therefore, the series was renamed IMSA Firestone Firehawk Endurance Championship, commonly known as the Firehawk Series, after the Firehawk performance tire brand. Total prize purses, year-end point funds and manufacturer contingency awards in 1991 amounted up to $1 million. As required by the sponsor, all cars were required to use its own Firehawk SZ or Firehawk SV tires which could be shaved to racing depth, or the all-season Firehawk GTX. Bosch and Kendall Oil were also associate sponsors. Most of the drivers that competed in the series were amateurs or semi-professional, whilst a few made their living out of competing in the series. Dorsey Schroeder and John Andretti are among the few full-time professional drivers who cut their teeth in the series. Meetings usually attracted over ninety entries and were often televised, the duration of the races varying from one two hour and a half event to one 24 hour race. The series would soldier on until 1998, by then known as Speedvision Cup, named for the former motosports-ortiented television network. During the sportscar racing "split" from 1998 until 2013, a rival series from Canada, the Motorola Cup, was sanctioned by the SCCA, with Grand-Am taking over in 2001. This is the other series that led to the modern Continental Tire Sports Car Challenge. There are three classes, sorted in order from the highest Grand Sport Class Chevrolet Camaro, Pontiac Trans Am, Nissan 300ZX (twin-turbo), BMW M3, Ford Thunderbird, Ford Mustang, Porsche 944, Mazda RX-7 (FC3S) Sport Class Pontiac Sunbird Turbo,Dodge Daytona Turbo II, Honda Civic CRX Si, Volkswagen Corrado Touring Class, Honda Civic Si, Audi 100 Quattro, Pontiac Grand Am IMSA Bridgestone Supercar Championship IMSA also hosted the Bridgestone Supercar Championship, sponsored by the sister brand of Firestone, Bridgestone, which was for higher-end sports cars such as the Porsche 911 Turbo, Lotus Esprit X180R, Chevrolet Corvette, Mazda RX-7 and Nissan 300ZX and was run between 1991 up until 1995. Usually a televised support race to the GT