Shimano freehub swap - do I need this thin washer?
11-13-23, 05:31 PM
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Shimano freehub swap - do I need this thin washer?
I've got a wheel with an 8/9/10-speed freehub running a 7-speed cassette with a spacer, and a wheel with a 7-speed freehub that I'd like to use in a 10-speed system. Both are older Shimano wheels so I figure I'll just swap the freehub and the drive-side cone assemblies. This all seems fine, but I've run into one question: behind the 7-speed freehub there was a washer with flat sides. Do I need this washer? If so, do I keep it with the freehub, or with the wheel? Any other concerns with doing this swap? Although the 10-speed hub is longer, the cone sits further inside it, so I don't expect any issues with spacing or dish.
11-13-23, 05:42 PM
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Whenever I'm faced with something like this, I try to figure out WHY the part is there and WHAT is does.
Sometimes I'll "trial"assemble and check spacing and clearance or rubbing.
Not being able to do that, and lacking arrears view of the freehubs, I'll speculate that it MIGHT be there to prevent the back of the freehub from biting into the shell. Or simply be a spacer to produce proper freehub/shell clearance.
Until or unless someone gives you a definitive answer, you.might assemble both ways and see what that tells you.
Sometimes I'll "trial"assemble and check spacing and clearance or rubbing.
Not being able to do that, and lacking arrears view of the freehubs, I'll speculate that it MIGHT be there to prevent the back of the freehub from biting into the shell. Or simply be a spacer to produce proper freehub/shell clearance.
Until or unless someone gives you a definitive answer, you.might assemble both ways and see what that tells you.
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11-13-23, 06:25 PM
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The hub in pic #1, with the plastic disk, appears to already have a washer on it, the black ring. You can check with a magnet.
I believe that the washer provides support for the hub shell by distributing the load of the freehub body, and/or help to seal the rear of the freehub body. Older Shimano EV tech document call it a 'freewheel body dust cap' and newer doc call it a 'freewheel body washer'.
In your case, probably keep it with the hub that it came with. If the hub in pic # already has a washer, don't swap it, the washers look to be different.
I believe that the washer provides support for the hub shell by distributing the load of the freehub body, and/or help to seal the rear of the freehub body. Older Shimano EV tech document call it a 'freewheel body dust cap' and newer doc call it a 'freewheel body washer'.
In your case, probably keep it with the hub that it came with. If the hub in pic # already has a washer, don't swap it, the washers look to be different.
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11-14-23, 11:20 AM
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I tend to use digital calipers when doing a mix-n-match freehub bodies to get an understanding how well the swap will end up.
I have not encountered that type of washer, it is odd but I imagine others have. The freehubs I have encountered that have a symetrical washer usually have a recess in the freehub for it to fit into. Without that recess the body will be sitting slightly out further than without it. This does result in slightly less spline engagement.
This is where taking measurements hub spline height, body spline depth, hub recess depth (noting chamfers), etc. you don’t want the body to bottom out on the splines.
Looking up the exact freehubs on Shimano’s Tech Docs May help you figure out the purpose of such an odd shaped washer.
The only thing on the swap that I’d look at a bit closer would be the cassette stops on the 8/9/10 body to the 7 body for spoke/spoke head clearance.
Finally, it does seem a bit odd if both wheels had an OLD of 130mm, especially the 7 speed. But I’ve had 7 speed135mm OLD so 130mm might not be that odd.
John
I have not encountered that type of washer, it is odd but I imagine others have. The freehubs I have encountered that have a symetrical washer usually have a recess in the freehub for it to fit into. Without that recess the body will be sitting slightly out further than without it. This does result in slightly less spline engagement.
This is where taking measurements hub spline height, body spline depth, hub recess depth (noting chamfers), etc. you don’t want the body to bottom out on the splines.
Looking up the exact freehubs on Shimano’s Tech Docs May help you figure out the purpose of such an odd shaped washer.
The only thing on the swap that I’d look at a bit closer would be the cassette stops on the 8/9/10 body to the 7 body for spoke/spoke head clearance.
Finally, it does seem a bit odd if both wheels had an OLD of 130mm, especially the 7 speed. But I’ve had 7 speed135mm OLD so 130mm might not be that odd.
John
11-14-23, 12:59 PM
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A bit more detail: the 7-speed hub is an FC-M550 and the 8-speed is an FC-MC38. The 8-speed hub is definitely 135mm OLD. I'm not quite sure if the 7-speed hub is 130mm or 135mm, it was available in both lengths with just a slight difference in axle length and an additional spacer. I'm using the original axle and non-drive side cone assembly (where the extra spacer would go for 135mm) so I'm hoping it will just work. The 8-speed hub came off a mid-90s mountain bike, and I'm swapping it onto a wheel for a 1992 Trek Multitrack.
11-14-23, 03:20 PM
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A bit more detail: the 7-speed hub is an FC-M550 and the 8-speed is an FC-MC38. The 8-speed hub is definitely 135mm OLD. I'm not quite sure if the 7-speed hub is 130mm or 135mm, it was available in both lengths with just a slight difference in axle length and an additional spacer. I'm using the original axle and non-drive side cone assembly (where the extra spacer would go for 135mm) so I'm hoping it will just work. The 8-speed hub came off a mid-90s mountain bike, and I'm swapping it onto a wheel for a 1992 Trek Multitrack.
Best recommendation is to keep the freehub spacer washer and NDS cone/spacers matched with the hub shell (which it seems you intended). And keep the drive side cone/spacers with the freehub body. This will keep the seals/interface together properly.
After install, check for the proper OLD and wheel dish. Expect that there may be minor changes since the relationship between the locknuts and the hub shell flanges may change. Adjust spacers stack as needed based on OLD and with consideration of how the dish will be affected (based on your personal preference of tolerance and ability to make dishing changes).
The FH-M550 is older MTB so has a slightly lower flange to flange width. Probably since it was 130/135 OLD. Not sure if the other FH is a MC38, looks more like MC18 based on the freehub body & washer, (but not really important).
Should work out OK, just expect to make minor tweaks.
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