Original sentence: The motorcycles raced in the championship are tuned versions of motorcycles available for sale to the public, by contrast with MotoGP (MotoGP is the motorcycle world's equivalence of Formula 1 racing whereas the SBK is similar to NASCAR) where purpose built machines are used
Edited sentence: The motorcycles raced in the championship are tuned versions of motorcycles available for sale to the public, by contrast with MotoGP (MotoGP is the motorcycle world's equivalence of Formula 1 racing whereas the SBK is similar to Touring Car racing) where purpose built machines are used