I use the Pre-runner E-locker on my truck at the dragstrip and have it locked at 100mph. Like rednecktaco said, its the turns that are the concern. When making a turn, the outer wheel needs to travel a further distance than the inner wheel. When locked, they will both turn equal amounts, which will cause the inner one to skip... and the driver to possibly lose control. If you practice driving with it locked up and understand what to expect under different conditions and know how to react, i think you should be ok.