Modifying 9 speed cassette to fit 10 speed freehub body


New Member
Jul 29, 2003
The new Shimano 10 speed aluminium freehub body, as used on Dura-Ace and now the Ultegra WH-R600 wheels, has splines that are too high for the older 9 speed cassettes to fit. However, the spline patterns are the same.

Has any one tried, or have an opinion on, modifying a 9 speed cassette by filing the spline grooves to sufficient depth to fit the 10 speed freehub body?

A 10 speed cassette will fit a 9 speed freehub body, but needs a spacer. Does this mean that the 10 speed freehub body is narrower than the 9 speed, so that a modified 9 speed cassette will be too wide for a 10 speed freehub body?

Are there any other reasons why a modified 9 speed cassette can't be used on an aluminium 10 speed freehub body?