One of the most important modifications to an EX500 racebike. Check the rules for your class! A 17 front and 17 rear gives you the best tire choices. Uses an 87/89 600R swing arm, an F2/F3 rear wheel, cush drive, rear brake caliper, and master cylinder, EX bell cranks and dog bones. If you send us the parts, you might save some money. The rear wheel and drive gear gets centered to the frame and engine. You also end up with captive spacers. A big plus when you change tires as often as a racer does.