[mikets]

Assuming the wheels are installed correctly (X pattern viewing from the top), it could be a software issue. The way we software calibrated our mecanum drive train is as the following:

• Make sure you put the PWM channels (or CAN IDs) in the correct sequence when instantiating RobotDrive(frontLeft, rearLeft, frontRight, rearRight).
• Put the robot on some 2x4's so the wheels can be freely turning without the robot running away.
• In code, execute MecanumDrive_Cartesian(0.0, 0.5, 0.0) and make sure all the wheels are going forward.
• If not, note the wheels that are turning backward and add the following line for each wheel that needs correction (need to change kFrontLeftMotor to the corresponding motors):
  SetInvertedMotor(kFrontLeftMotor, true);
• Now, write the teleop code that uses the joystick(s) to drive the robot.
• If tank drive, pushing the left joystick forward should turn the left wheels forward. If not add a minus in front of the joystickLeft.GetY().
• Do the same for the tank drive right joystick.
• If arcade drive, push the joystick forward should turn all four wheels forward. If they are reversed, put a minus in front of joystick.GetY().
• For arcade drive, push the joystick to the right and the robot should turn right (left wheels forward and right wheels reverse). If not, put a minus in front of the joystick.GetX().
• Similarly, for strafe, correct the corresponding joystick sign if it is not going the direction you want.