bobonker

Hi there,

A buddy of mine is letting me run his old Dura Ace WH-7800 wheelset. The problem I'm having is that my 9 speed Ultegra cassette does not fit on the Dura Ace freehub body. There is "step" in the freehub body that prevents the cassette from sliding all the way down.

I have an almost new 9 speed Shimano freehub mounted on an Alex hub and I figured I could just transplant it over, but I'm running into multiple problems.

1. On the Dura Ace hub, I removed the outer locking nut that holds the freehub on (using a 5mm allen wrench). After doing this, I can lift the freehub body away from the hub, but it will only move about 1/2" off before it gets stuck. I'm hesitant to force anything.

2. On the Alex hub, I've removed all of the internals, but I can't get the freehub off. A long 10mm allen wrench slides right through, but there is nothing to grab. So, I tried a 12mm allen. Before I continue though, I'm wondering if this will even work. The Dura Ace axle is large and hollow. The Alex axle is thin and solid.

I really hope I can run this setup because these wheels are a sweet upgrade over what I currently have.

Any tips/advice would be much appreciated.

Pics:



Bob

Ingleside

Sorry to tell you but its not going to happen. The Dura Ace freehub is completely different than the one on the Alex hub. You either need to upgrade to 10 speed Shimano to get that wheel to work or ditch the wheels.

bobonker

Man, that's a bummer. Thanks for the quick response.

Looks like I'm not the first to run into compatibility issues with the 7800 freewheel body. Several old posts outline peoples' frustration with this design.

Regarding the freehub body...any idea why I can't remove it?

https://techdocs.shimano.com/media/te...9830607464.pdf

That doc says that all have to do to remove it is remove the outer fixing nut and spacer and then I can replace it. It moves some, but won't come completely off.

Thanks,
Bob

Kimmo 

Couldn't you make your shifters work with 10spd spacing via a Shiftmate or possibly alternate cable clamping?

Are those deeper splines only for the spider-mounted cogs, or can you get individual cog cassettes to fit?, If so, you could respace a 10spd cassette with nine cogs...

Or maybe you could cut the splines in a 9spd cassette deep enough to fit... that'd be a bastard of a job, though

bobonker

Or...I could machine the splines down on the existing freehub (which is why I'm trying to remove it). That would solve the existing compatibility issue and all future ones, too. It'd be an easy job in a lathe and the guy I got the wheels from is a top-notch machinist. The only issue I can see is that I don't know what is inside the freehub and whether it would tolerate being spun in a lathe without tossing its guts all over the place.

Bob

Ex Pres 

You don't only have a spline issue, but IIRC the 10s only freehub body is also 1mm shorter than an 8-10s body as a 10s cassete is narrower than an 8-9

AEO

no, don't do that. WH-7800 splines are made from aluminum and won't withstand the amount of force the steel cogs will put on the splines.
The splines get chewed up, and eventually the cogs just cut right through.

AEO

this won't work unless you can find a freehub that is designed in a similar fashion.
by the looks of it, the freehub on the WH-7800 is a silent clutch type, but not like the ones you can find for HB-5600/6600/6700.

maybe try and find the docs for WH-7850, which is an updated WH-7800 with a titanium, low profile spline freehub. They might be similar, they might not.

helicomatic

The 7800 freehub bodies have the pawls on the back, and the ratchet ring is in the hub shell itself, unlike almost all other Shimano rear hubs. The 7850 freehub body is the same one on the XTR rear hub FH-M975, and attaches to the familiar splines. They're not compatible.

Kimmo 

If you're extra-keen, you could turn the splines down, then mill away the load-bearing face of the splines and epoxy steel strips in there... but that's getting pretty silly

DannoXYZ 

Exactly, the design of the alloy freehub is that way for a reason. If you simply substitute aluminium for steel and build it to the same shape, you'd end up a freehub that looks like this after some use:

https://www.sheldonbrown.com/images/aluminum-body.jpg

Actually no. A 10-spd Shimano 10-spd cassette measures 37.15mm across on the outer edges. A 9-spd Shimano cassette is 36.5mm wide, or 0.65mm narrower than the 10-spd. The reason you have to use 1 mm shim when installing the 10-spd cassette on some freehub-bodies is due to the design of the 10-spd cog-carriers for the largest cogs. It actually places the cogs over the inside edge of the freehub-body closer to the spokes. This end up placing the top-cog on the 10spd cassette closer to the spokes than the 9-spd one, giving the illusion that the 10-spd is narrower when it really isn't. The further-in 10-spd cassette ends up causing a gap between the top-cog and lockring on some freehub-bodies, thus requiring the 1mm spacer.

Additionally, the hanging-over-the-inside-edge feature of the 10-spd cassette-carrier ends up rubbing on the stationary part of the freehub-body on some freehubs, giving you a 10-spd fixed-gear wheel.

bobonker

Thanks for all of the input, guys. I've shelved the idea of running these wheels. It's not worth converting my bike to a 10-speed setup. I'll pick up some Ksyrium SLs instead.

Bob