[camcojb]

they have you go backwards beyond 50 degrees so you're going clockwise (the direction the engine is normally running) when you're reading your numbers. This eliminates the slop in the timing chain from turning backwards and then going forward that would throw your readings off.

I've degreed with the small cheap wheels and they work, but I much prefer the larger diameter aluminum wheels; much easier to read and more accurate in my opinion; the larger the diameter the more accurate the markings will be.