I tried some "AFX Silicone rear tires also fits JL X-traction rear hubs" from Bud's HO and the quality is ok but they have a larger radius than the stock tires which reduces the magnet power. The net effect is better acceleration on the straights but less traction in the corners.

Use Weidr Jacks Rocket Science Butt Uglies.

http://www.geocities.com/jack.stinson@sbcglobal.net/bh.htm