rocketgeek:
The right way to do this is to measure the speed of each wheel and use a PID library (Arduino Playground - HomePage) to set the PWM output to each motor in order to obtain a commanded motor speed. This is a nice way to do it because you can change the setpoints at will to change the speed or to steer (use different commands).
Thanks , I looked online for an example of how to use pid lib to sync the motor speed but failed to do so... Do you know any good example for it??