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Dura Ace 7400 8 speed/ 7800 hub

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Dura Ace 7400 8 speed/ 7800 hub

Old 01-27-14, 09:13 AM
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riceman
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Dura Ace 7400 8 speed/ 7800 hub

I have a bike with Dura ace 7400 8 Speed group set. I have a set of dura ace wheels with D/A7800 hubs I tried to put the D/A 7400 8 speed cassette on the D/A 7800 wheel but can't seem to get it to fit.? I thought all 8/9/10 cassettes fit fit the same hubs. Is there any way to use my 8 speed cassette on the D/A 7800 hubs?

Appreciate any help
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Old 01-27-14, 09:16 AM
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There are a few DA hubs that are 10s only, I think the 7800 is one of those. It's pretty sneaky but @RobbieTunes will show up and tell you how to alter it to get it to work. It involves filing the hub I believe but don't quote me.
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Old 01-27-14, 11:03 AM
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IIRC, the 7800 series freehub body has a deeper profile spline for more purchase with the titanium spiders of the DA cassettes. I think the body is also titanium.
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Old 01-27-14, 12:02 PM
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Originally Posted by shoota View Post
There are a few DA hubs that are 10s only, I think the 7800 is one of those. It's pretty sneaky but @RobbieTunes will show up and tell you how to alter it to get it to work. It involves filing the hub I believe but don't quote me.
Because the 7800 freehub body is aluminum, it has taller splines to hold up better against the forces exerted on it by the cassette . Thus is accepts only 10-speed cassettes. I personally wouldn't file the freehub body as then there won't be as much material to hold the cassette cogs and you might get cogs carving into the freehub body splines - especially any cogs that are "loose" when the cassettte is apart (IIRC, the biggest 5 cogs are held together with small allen screws but the 6th, 7th, and 8th cogs are all separate).

Edit: I think I'd go the other way and Dremel or file the notches in the cassette cogs.

Last edited by Gonzo Bob; 01-27-14 at 12:09 PM. Reason: add recommendation
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Old 01-27-14, 12:12 PM
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Originally Posted by Gonzo Bob View Post
Because the 7800 freehub body is aluminum, it has taller splines to hold up better against the forces exerted on it by the cassette . Thus is accepts only 10-speed cassettes. I personally wouldn't file the freehub body as then there won't be as much material to hold the cassette cogs and you might get cogs carving into the freehub body splines - especially any cogs that are "loose" when the cassettte is apart (IIRC, the biggest 5 cogs are held together with small allen screws but the 6th, 7th, and 8th cogs are all separate).

Edit: I think I'd go the other way and Dremel or file the notches in the cassette cogs.
To be more specific it only takes 7800 series 10 speed cassettes. There are plenty of 10s cassettes that will work 0n 74XX, 77XX, 785X and 79XX hubs.
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Old 01-27-14, 01:31 PM
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Those wheels have been turning up as unwanted orphans at low prices for many years. Their lack of back-compatibility gave Shimano some well-considered second thoughts, and they soon returned to using their proven steel and titanium freehub bodies (that thankfully also don't require the much stiffer axle needed with the bulbous "Campag-style 4-bearing freehub").
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Old 01-27-14, 02:52 PM
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Originally Posted by dddd View Post
Those wheels have been turning up as unwanted orphans at low prices for many years. Their lack of back-compatibility gave Shimano some well-considered second thoughts, and they soon returned to using their proven steel and titanium freehub bodies (that thankfully also don't require the much stiffer axle needed with the bulbous "Campag-style 4-bearing freehub").
I see lot of these wheels and other orpanied DA 7800 stuff turning cheap also. A lot of it is even getting donated to the local bike coop for free. While really nice stuff it just isn't worth a lot because it is only really fully compatiable with other 7800 stuff. It has likely frustrated many who thought they got a deal on some really nice DA stuff cheap.
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Old 01-27-14, 04:33 PM
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Is it possible to change the free hub body to one that would work with the 8 speed.

cheers
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Old 01-27-14, 04:55 PM
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Originally Posted by riceman View Post
Is it possible to change the free hub body to one that would work with the 8 speed.

cheers

No, although some of the lower-tier, 10sp Shimano wheelsets from the very same period used their traditional-style steel freehub body, attached by splines and hollow bolt, and with a conventional Shimano freehub axle assembly.

I believe that even the ball bearings supporting the axle in the 7800 hubshell are designed around a larger-diameter ball track, due to the use of a thick aluminum axle that is stressed nearer to it's center.

Last edited by dddd; 01-27-14 at 05:02 PM.
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Old 01-27-14, 05:42 PM
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Because Shimano switched to 2mm deep splines in lieu of 1mm deep splines for those years, other makers did, as well. I know of Zipp and Formula doing the same thing on some models. It's not too bad if you pick up these 10-sp only wheels at a great price now, as there are plenty of cassettes available and 10-shifters and RD's are now widely available used, at good prices.

However, 3-4 years ago, that was not true. I picked up a great set of wheels for $60 that were only 10-sp compatible, from a bike shop employee who swore they were 8/9/10, then swore at me when I asked for a refund. The deal was outside the realm of the shop, but he knew better. I've since answered several ads for great prices on wheels, and in 2 cases have discovered they were 10-sp only. Only recently has there been cheap used 10-sp gear to use with those wheels, and I made a nice bike out of them and sold it. You'll often see these wheels for sale "cassette included."

I've had the 7400 8/9/10 wheels, the 7700 8/9/10 hubs, the WH-7700 wheels (8/9/10) and now run a set of C24 7900's and a hand-built set on 7900 hubs. Part of that hand-built set was paid for by the DA 7800 wheels I got for $175 and had a heck of a time flipping for $325, "cassette included."
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Old 01-28-14, 05:41 PM
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Thank you for all your help. Much appreciated.
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