Bruce Jenner -- I'm Trading My Wife for a Sick New Car!!!!

Bruce Jenner just went out and did what all men do when their woman is finally out of the picture ... drop $50k on a sick new toy.

Bruce bought a NASCAR-approved UTV race car. Kris Jenner's soon-to-be ex bought it from 928 Powersports who built it for NASCAR superstar Robby Gordon. And we're told it was an impulse buy ... we're guessing a celebration of sorts.

Bruce made the deal Monday at the Sand Sports Super Show in O.C. ... the same day Kris filed divorce docs. And, our spies on the ground tell us Bruce was literally grinning from ear-to-ear.

The Olympic gold medalist is a speed freak ... as in hardcore race fanatic. We're told he plans to break in his new speedster in February at the Griffin King of the Hammers in Johnson Valley, CA with sons Burt and Brandon.

Being single does have its privileges ... many privileges.