|see the brake band on the left (back of wheel)|
and the thicker drive band on the right (front of wheel).
to find your wheel's drive ratio:
turn the wheel slowly with your hand for one full rotation, counting the number of rotations the flyer makes.
as an example of what this means, if i were to draft an inch of fiber for every turn the wheel makes, my yarn would have 6.5 twists per inch. the thinner the yarn, the more twist it needs to hold together properly. if i want to spin thinner, i need to either treadle faster or draft slower to increase the drive ratio and give me a higher twist.