Dura Ace 7850 freehub replacement

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hitchhiker
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Dura Ace 7850 freehub replacement

Postby hitchhiker » Sun Nov 11, 2018 5:26 pm

Hi, I need to replace the freehub on a set of 7850 wheels, does anyone know if I have to use a dura ace part or are there other options?

I’m not fussed about saving a few grams and would prefer a cheaper option than the $200 plus for a titanium dura ace part

Thanks

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Tim
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Re: Dura Ace 7850 freehub replacement

Postby Tim » Sun Nov 11, 2018 8:09 pm

I think you might be out of luck finding any other compatible and cheaper freehub.

Sheldon Browne's words:

"Virtually all Shimano Freehub bodies are interchangeable. The exceptions are:
....
....
....
FH-7850 and FH-7900 Dura-Ace bodies, which have returned to a splined attachment between Freehub body and hub shell, but it is larger than the usual one. It is similar but not interchangeable between these two models.
...."

Shimano Tech Docs show that the FH-M970 freehub is interchangeable/identical to the 7850, being titanium and XTR level, it is also expensive.
http://si.shimano.com/pdfs/ev/EV-FH-7850-2714A.pdf

Duck might be along to clear matters up, but I don't think it'll be good news, unless he's got an old one sitting in the junk box.
Maybe try negotiating a price with some of the ebay or other sellers.

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Duck!
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Re: Dura Ace 7850 freehub replacement

Postby Duck! » Sun Nov 11, 2018 8:44 pm

Digging through the Shimano tech docs, it appears that 7850 and XTR M970 through to M9000 quick release versions use the same body (M988/M9010 through-axle variant is different). Interestingly, there is - officially at least - no compatibility between 7850 and 7900, which I would have thought more likely to be compatible than crossing between Dura-Ace and XTR. I do know that XTR hubs (and apparently 7850 by extension) have a longer spline interface between the hub shell and freewheel body than at least some Dura-Ace, so maybe that's why the 7900 body won't fit; its female splined recess is too shallow to match with the hub shell properly.

There is no cheaper alternative because Dura-Ace/XTR used a larger diameter axle than all other hubs of their vintage, so nothing else will fit.
I had a thought, but it got run over as it crossed my mind.

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hitchhiker
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Re: Dura Ace 7850 freehub replacement

Postby hitchhiker » Sun Nov 11, 2018 8:56 pm

Thanks for the replies, sounds like bad news

My problem is an earlier owner of the wheels filed down the freehub to take an 11 speed cassette, the ridge at the bottom of the freehub is so low that the cassette binds up against the hub outer face. I run them 10 speed with a spacer so thought a new freehub would solve my problem

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