There are a few important specifications in the bicycle world that range in ease to find. Shimano Hyperglide spline, Hayes 6-bolt rotor, e*thirteen ISCG05, etc.
Some of these have clear and openly defined specifications. Others don’t. One of them that has become crucial for many in the past few years is the Cannondale BB30 crank spline.
SRAM has used this for a while, with BB30 cranks and DUB cranks. Many small brands in the current market work with it. Some have more information or better information than others.
Anyone working in the crank space for the last decade has needed this elusive and difficult to measure spec. I’ve wasted too many hours searching for it. I did my best to reverse engineer it.
Suddenly, the hunt for this pirate treasure came to an end last week. Tim Lane of Digit Bikes posted some information about this on Instagram. I immediately reached out to him for more information. Tim responded quickly.
And there it is, the OEM drawing (anonymized).
I spent some time with this. It’s a confusing interface drawing but it is simple at it’s core.
I updated my DUB spindle drawing with the new information. I was off 0.01mm on a diameter and 0.4 degrees on the taper. Close, and would have passed inspection. It’s good now.
The DUB pattern is identical to BB30, just with the tops of the outer spline clipped for the 29mm OD.