jonwvara 

Thanks to a fellow bf member, I'm about to rebuild a Suntour sealed bearing rear hub--which came to me with a broken flange--with a new hub shell/bearing assembly. I'll be switching the axles, since the donor hub has a solid axle, not a quick release one.
I figured that while I was at it, I might as well re-space the hub to accept a 7-speed freewheel rather than the original 6 speed. I've done that many times with cup-and-cone hubs--move 3 or 4 mm of spacers from the non-drive side to the drive side, adjust the hub, re-dish the wheel, and you're good to go.
In this case, though, there are a couple of problems. For one thing, there are no spacers on the non-drive side--just a thick (6mm) steel locknut the bears directly against the notched aluminum bearing compression plate, if that's what you'd call it (I've seen that aluminum part referred to as a "locknut" as well, but it seems to me that the steel nut outboard of it is the real locknut, properly speaking). Okay, that may not be a big problem. It shouldn't be hard to find a thinner 3-mm locknut, use it in place of the original, and add 3mm of spacers to the drive side.
But...that would also involve getting a good enough grip on the aluminum compression plate to loosen the steel locknut on that side. Unless you do that, you can't add the spacers and re-center the axle. (Sticking with 6 isn't a problem--you just work exclusively from the drive side, and leave the non-drive side alone.) Naturally, I don't have the special tool, although our man Sheldon say that it's not necessarily easy to loosen it even WITH the right tool.
Maybe I should leave well enough alone. It may even be that this is the C&V gods' way of telling me to stick with 6, since this wheelset is intended for my Miyata 912, which I've run for years with 7-speeds, though it was of course originally meant for 6.
Anyone have any good ideas for dealing with the aluminum compression plate (again, that's my descrition of it, not Suntour's official name)? I don't want to file flats it it, bang it with a punch, or otherwise beat it up in any way.Suntour Sealed Bearing hub axle low res..jpg

Zaphod Beeblebrox 

Unless you are going from a Suntour Ultra6 (which is the same width as 5 speed) to a standard 7 speed freewheel you shouldn't need to move any spacers at all.

Standard 6 speed and 7 speed freewheels are the same width.

desconhecido 

Have you tried the hub and 7-speed freewheel on the frame to see if it fits? Many times it will as the 7-speed freewheel isn't very much wider than a 6 because of the smaller space between cogs (5mm center-to-center as opposed to 5.5mm). If you need a bit more space on the drive side, 2mm should do and you could just add that to the drive side and leave the left alone. You will still be able to fit the hub into the frame easily. That's what I'd do, anyway.

jonwvara 

You're partly right. The overall width is the same--you can use either 6 or 7 speeds with a 126 spaced frame--but the 7 speed is several mm wider, so when you upgrade from 6 to 7 you need extra spacers on the drive side to keep the chain from rubbing against the dropout or chainstay.

Zaphod Beeblebrox 

I've never needed to so I Guess I've just been lucky two or three times!

desconhecido 

I think it depends on the frame. We have a Bianchi that came with a 6-speed freewheel and a 7-speed fit with no adjustment and no difficulty. On another bike we have, though, the chain interferes with the stays when on the smallest cog.

About that width -- six cogs at 5.5mm c-c gives 27.5mm from small to large, c-c. Seven cogs at 5.0mm c-c gives 30mm. So, a 7-speed freewheel should be, at most, 2.5mm wider than a 6-speed.

robatsu

I've had a similar problem using an Ultra 6 on a 120mm hub in my Mondia Special frame. I had to space the hub out to about 122mm to avoid chain/stay interference on the smallest cog.

Chombi

I guess, depending on the design of the hub, a 7 speed frewheel will work with most 126mm spaced hubs. At least with a Mavic 550 rear hub it does, as I found out on my bike build-up last year. It looked close but it worked out great. The 7 speed freewheels have narrower cog spacing to make it fit on 126mm hubbed bikes, but you will have to use a narrow chain so the system shifts good.

Chombi