Wheel - 7sp to 9sp - Must I re-dish?
 

So I've got an old 7 speed rear wheel with a crapped out RX100 freewheel (ok, I can't ever remember which one is a freehub and which is a freewheel - but it's the modern sort, just for 7 speed, circa 1992).

If it doesn't prove to be too difficult, I'd like to rebuild it using whatever cheap and/or used parts I can get my hands on, to use as 9 speed - to have with a turbo trainer tyre just for trainer use.

My question - can I just replace the freewheel (freehub?) with a 9-speed one? Is the difference in width there what makes rear dropout spacing wider on modern bikes? Or will I have to re-dish the wheel?

If I'd have to re-dish the wheel, I figure I'm probably better off just picking up some old 9-speed hub from e-bay and replacing the whole hub. Wouldn't be a bad way to teach myself wheel building, I suppose, either.

Any other options?

the width of the 9sp cassette is wider, it won't work right.

what material is your frame. if it's steel then just buy a rear wheel, unless you really like the other parts on the wheel

8-9sp ==> 130mm spacing(road hubs)
7sp ==> ~127mm spacing

check sheldon browns site

i don't know what a rx100 is?

You can re-use the entire wheel, including the RX100 hub, but to update to 9 speed you'll have to replace the freehub with the 8/9/10 speed freehub referenced by revolator. The RX100 hub will accept the new freehub but you'll have to redish the rim. Still, that's a heckofalot less work than rebuilding with a new hub and it will cost less.

Frame is fine. It's getting a 9 speed cassette on the wheel which is the issue. And the whole point is to save cash by not buying a whole new wheel.

RX100 used to be the groupset below 105.

Excellent - that's what I needed to know.

Don't know about costing less though - I expect the cheapest way to get my hands on a freehub will be to buy a whole used hub and pull the freehub off it - not many freehubs floating around on Ebay by themselves really.

No real point in buying new - I'm only going to use it on the trainer so as to avoid wearing out my 'real' tyre and not deal with the hassle of switching back and forth with one of those training tyres.

+1

Treefox,

if you can work the redish yourself, and replace the freehub, then thats the way to go.

If your getting someone else to do it, the price of a good used rear wheel might not be much different and less of a hassle. If the frame is aluminum, they advise not to use a rear wheel that doesn't match the spacing.

Bingo! That's what I do. I buy the entire hub off ebay, then remove the freehub and place it on the wheel I want to upgrade.

For any who may come after me, if the search function ever really works:

After a bit of rummaging around Sheldon's site, I found this: http://sheldonbrown.com/k7.html

Pretty much all that one needs to know is about 3/4 of the way down.

new rear wheel on ebay $38 + shipping as of now, expires in ~5hrs

ebay


Mentions Sora hub, but I'm not sure it's a 8/9/10 sp? Also the picture side doesn't show the freehub.
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freehubs (new)
jensonUSA

air bomb

Here is an even cheaper alternative. Since the wheel is destined for a trainer, do you really need all 9 cogs? If 8 of them will do, you can install 8 cogs from a 9-speed cassette on a 7-speed freehub body.

Get a 105-level 9-speed cassette (HG79) since all of the cogs are "full plate" and none are combined on spiders. You can remove which ever single cog, and it's spacer, you can get along without (except the smallest) and install the remaining 8 on the current freehub body.

The cog spacing and chain width requirement will still be 9-speed but you won't have to change your freehub or redish the wheel.

At full bike shop retail a 105 freehub body is only about $30.00. Tiagra is about $23.00.