Well, there are various upgrades for the ZipZaps, like motors and gears and tires or what not.
I would recommend upgrading your motors, going form the lowest rpm's to the highest rpm's, so you can tell the difference between them all.
Gear ratios: The red gears are the fastest, the blue are the slowest, the green are in the middle.
I created a thread for gear ratios and motors or what not, lemme find the link for you.
[Edit] I found it, it's hosted @ Bitpimps.
http://bitpimps.lixlink.com/pages/ph...pic.php?t=2938
Chuckster...