Question: Where should the big toe joint be relative to the middle of the cleat? Should I position my foot so the pedal axle is below the bulge of the joint or just behind it? -- Ashley B.
Coach Fred Matheny Replies: The pedal axle should be directly under the ball of your foot or slightly behind it. For most people, this corresponds to a position about a quarter-inch behind the bulge of the big toe.
Generally, if your feet are smaller than size 9, go for a position directly on the ball of the foot. Longer feet need more stability, so a slightly rearward cleat position usually works better.
Experiment to see what feels efficient and comfortable.
Note, too, that positioning the pedal axle behind the ball of the foot is an effective way to relieve the direct pressure that causes "hot foot." If you experience this burning sensation on long rides, try moving cleats rearward.
A few different RBR eBooks provide an array of bike fitting information, including detailed instructions on cleat mounting, how to install a shim if you have a leg-length inequality, etc: Andy Pruitt's Medical Guide for Cyclists, Bike Fit by Coach Arnie Baker, and Bike Fit 101 by Coach Rick Schultz.