Do you do anything special to make your robot turn? Normally all those wheels on the ground would make turning difficult. We found that our Bosch got really hot (while the chip's were relatively cool) we solved that problem by cutting the power to the bosch in half, now both the bosch and the chip's get equally hot under strenuous circumstances.
We have a six wheel design (have for every year), and offset the center wheels by 1/4" so the robot is actually balancing on the center wheels: makes for easy, friction free turning. GOtta use the Gyro for stabilization, however, because it turns TOO easy!
Photos at
http://www.barello.net/FIRST/Images