Simplify the following text for a Grade 6 native English-speaking person.
Original: During the 1980s , Tilke competed in touring car racing , mainly on the old NÃ 1\/4 rburgring Nordschleife circuit .
Simplified: During the 1980s , Tilke competed in touring car racing . Most of his racing was on the old NÃ 1\/4 rburgring Nordschleife circuit .