Hollowtech’s twin pinch bolts, or the alternative one bolt fixing a crank to an integrated spindle (eg. It has further evolved into the more sophisticated square-taper wedge but then disappeared when integrated cranks were introduced. The wedge-bolt that is the cotter pin still does the job of fixing cranks to the spindle on a limited range of low end - or classic - bikes. Wedges have been an efficient means of connecting bike components over the years. Wheel axles aside, then, bikes rely on spindles with the bottom bracket being the most important point of installation. The hub’s outer race attached to the spokes rotates around the ball bearings allowing the wheel to turn freely. They are fixed against the inner race of the wheel hub bearings on one side, and bolted or clamped into the dropout on the other. Wheel axles are the most instantly recognizable axles on a bike. While the earth’s axis is an imaginary line, axles on bikes have a mass and diameter, although they also center on an imagined point. Think of an ‘axis’ as in the earth’s axis-the earth revolves around its axis which remains stationary at its center. The definition of both axle and spindle is clearly contained in the words themselves even thoughĪn axle is a stationary rod around which components rotate. Integrated Crank Spindles – 24mm, 30mm, 28.99mmīefore we get into details, let’s firstly take note of the important distinction between axles and spindles.Three Types of Bottom Bracket Spindle – Wedges (2) and Splines (1).Axle or Spindle?-What’s the Difference?.But also a description of the present since most forms of BB and crank spindle that have appeared since Starley developed his safety bike, are available today in one form or another. I’ll confine the discussion to bottom brackets and cranks, leaving out pedal spindles, and trace the key developments in design down to the present. A bike spindle refers to one of three things:Īlthough the term “bike spindle” is not used amongst industry insiders, I’ll treat it as though it is.

Cotter pins bicycle