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Shimano Dura Ace 7800 replace to 7850 or 7900

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Shimano Dura Ace 7800 replace to 7850 or 7900

Old 06-18-10, 11:29 AM
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Shimano Dura Ace 7800 replace to 7850 or 7900

Hello,

I wonder if DA rear hub 7800 freewheel body can be replaced with 7850 to accept 9-speed not only 10 speed cassettes? Replaced to 7900? Thanks for your reply.

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Old 06-18-10, 01:55 PM
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I don't understand you want to replace with 9-speed 7900? As far as I know 7900 is ten speed.
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Old 06-18-10, 02:17 PM
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Originally Posted by v70cat
I don't understand you want to replace with 9-speed 7900? As far as I know 7900 is ten speed.
7800 and 7801 have tall splines because shimano found out that aluminum freehub bodies get gouged by steel cassettes with the 1mm splines. Tall 2mm splines are a 10sp only feature since 7700 used a steel freehub body and only needed 1mm splines.

7850 and 7900 use titanium freehub bodies with the conventional 1mm splines.
8/9/10sp freehub bodies are the same width, and the only thing that makes 7800 freehub bodies 10sp specific are the 2mm tall splines.


and no, you cannot interchange DA freehub bodies between 7700, 7800, 7801, 7850 and 7900, they're all different. You can checkout the exploded view of DA hubs at shimano tech docs to see what I mean.
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Old 06-18-10, 02:17 PM
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I was specifically told by Shimano Technical Department that you can't replace the freehub body on the 7800 with the 7900. The 7800 is only for 10-Speed cassettes and we are all stuck with it.
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Old 06-18-10, 02:24 PM
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as for one reason you might want the normal 1mm spline freehub body, SRAM doesn't offer their 10sp cassettes with tall splines.
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Old 06-18-10, 04:49 PM
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The 7800 series hubs had their drive side bearings moved inboard to allow the Al freehub body so the later and earlier freehub bodies are incompatible with it.
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Old 06-18-10, 04:55 PM
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Thanks AEO. That makes wheel purchase decision really easy. Or should I move on, and upgrade to 10-speed? Nay, too costly.
Thanks everybody for your replies.

Originally Posted by AEO
7800 and 7801 have tall splines because shimano found out that aluminum freehub bodies get gouged by steel cassettes with the 1mm splines. Tall 2mm splines are a 10sp only feature since 7700 used a steel freehub body and only needed 1mm splines.

7850 and 7900 use titanium freehub bodies with the conventional 1mm splines.
8/9/10sp freehub bodies are the same width, and the only thing that makes 7800 freehub bodies 10sp specific are the 2mm tall splines.


and no, you cannot interchange DA freehub bodies between 7700, 7800, 7801, 7850 and 7900, they're all different. You can checkout the exploded view of DA hubs at shimano tech docs to see what I mean.
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Old 09-29-10, 06:49 PM
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Originally Posted by LUCAS
I was specifically told by Shimano Technical Department that you can't replace the freehub body on the 7800 with the 7900. The 7800 is only for 10-Speed cassettes and we are all stuck with it.
I don't mind be stuck with the 7800. It functions perfectly. I knew going in it was only 10 sp compatible.
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Old 09-29-10, 08:08 PM
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Originally Posted by Paul Y.
I don't mind be stuck with the 7800. It functions perfectly. I knew going in it was only 10 sp compatible.

Being stuck with it means that Shimano eventually won't support it with parts (think freehub).
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Old 09-29-10, 08:23 PM
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Paul Y: Wait til the 7800 freehub bodies get all cheap, then buy a pile of em.
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Old 09-30-10, 10:55 AM
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Originally Posted by surreal
Paul Y: Wait til the 7800 freehub bodies get all cheap, then buy a pile of em.
That+1
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