Originally Posted by
rccardr
I suggest caution with regard to Dura Ace 10 speed hubs. IIRC, 7800 hubs are limited to DA/Ultegra 10 speed cassettes due to the taller splines.
Yes, the FH-7800 uses a aluminum freehub body that had the taller splines to prevent the cassettes from damaging the body. This limits the compatibility, and will not allow the use of most common Shimano HG or HG compatible cassettes from other manufacturers. This limitation means that speed will be limited to 10 speed only.
Dura Ace FH-7402 takes a special 8 speed cassette and requires a threaded outermost sprocket.
Other models of Dura Ace FH (7403, 7700, 7900) don't have the same cassette compatibility limitations but could present a problem if the freehub body needs to be replaced. The DA models use a different mount from most Shimano models and accepts only certain freehub bodies. Since these are usually quite old, parts availability is very scarce and expensive.