Correct spoke lengths are a fundamental attribute of high quality handmade wheels. Spoke manufacturers typically produce spokes in 2mm increments. While you can get lucky with a standard spoke length, often spokes will be too short or too long. If a spoke is too long it will bottom out on the nipple leaving room for no further adjustments. This can create a stress riser on the first thread and cause a spoke to break at the nipple. If a spoke is too short, the wheel will have weak thread engagement with the head of the nipple is unsupported with the potential to crack off. As the threaded section of a spoke is only 9mm (19 threads), a 2mm error in spoke length is a significant problem.
We cut and roll exact spoke lengths using the Morizumi Spoke Cutting Machine. This machine cold forges spoke threads using same thread rolling processes used in industrial spoke manufacturing. To calculate our spoke lengths, we measure all wheel component to within 0.1mm to pick up variations in manufacturing tolerances and to quality control each component. We calculate spoke lengths using the industry standard formula celebrated by Jobst Brandt in The Bicycle Wheel and adjust this calculation based upon on our knowledge of variations in spoke elasticity, nipple design, and the effects of some spoke lacing patterns.