Make sure you have the wheel dead centre before you start with the assigning. It should then let you assign negative X to left and positive X for right turns. Our support guys should be able to offer more detailed advice.
Edwin
Still haven't got it. It appears that my iMac notices that there is a Logitech Momo connected to it, but can't take any input from it. On my MBP on OS X (10.7), it's able to read it and take the signal, but it's hyper sensitive when turning left - turning right is normal. Accelerator and brakes are normal too.
But when I switch over to XP on Bootcamp, it works perfectly after a brief calibration.
So not really sure what my problem is here. I'm confident my Momo is working fine, there just doesn't seem to be the support on my macs, particularly my iMac. Is there any software to check the signal and calibration of steering wheels on macs?