Update to Bolt Circle Diameter Cribsheet

We have reviewed the bolt circle diameter cribsheet, checked bolt-hole spacings using trigonometry and made some corrections. Apparently, the spacings were measured rather than calculated based on angles — and measurement is never exact! We have also added entries for several new patterns. Some of the new ones with uneven spacings had to be reverse-engineered from photos and, though we think that we have them right, we welcome feedback.

Measuring bolt-circle diameter

Measuring two holes away, right side to right side (or left side to left side) gives the most accurate result with a 5-bolt chainring.

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