Let's review some basics again. Here is a tip for dead reckoning using the two driving motors to go straight or turn.
"TEST YOUR MOTORS. Firmly mount your motors in a fixture and run them simultaneously with a Lego beam mounted like the minute hand on a clock. Place move blocks in a loop that rotate the motors in 1 degree increments in a full circle. If the motors are aligned, them the pointers will be aimed in the same position. Also try rotating the motors in 90 and 180 degree increments.
Pick the 2 that are the most closely aligned as your drive wheels. "
- quoated from "Coach David" in FLL Forum (post #10)
http://forums.usfirst.org/showthread.php?t=13137
