stephen, it is in the manual on page #22:
"TO ADJUST BRAKE
Your tractor is equipped with an adjustable brake system which is mounted on the right side of the transaxle. If tractor requires more than six (6) feet stopping distance at high speed in highest gear, then brake must be adjusted.
• Depress clutch/brake pedal and engage parking brake.
• Measure distance between brake operating arm and nut "A" on brake rod.
• If distance is other than 1-1/2", loosen jam nut and turn nut "A" until distance becomes 1-1/2". Retighten jam nut against nut "A".
• Road test tractor for proper stopping distance as stated above. Readjust if necessary." You can download the manual from here. Hope this helps, good luck.