Just thinking out loud really....
I have a 7sp commuter bike. Now, an 8sp cassette won't fit the freehub, that much I know. BUT I have a couple of 8/9 sp freehub bodies chucking about.
In therory, if a 9sp body fits the hub, all I have to do is bugger about with the axle spacers and possibly re-dish the back wheel for it to work, yes?
(I have an 8sp cassette, chain is the same, so I only need a new shifter)
Why bother? True enough, but why not, just to see if I can? 😀
Yes I'm pretty sure I did this with an old STX hub a few years ago. I might be wrong though. It might have been Mountain LX. Can't remember.
Sure there isn't a spacer of the 7 speed freehub?
I didn't think Shimano still made 7-speed freehubs. I thought cheaper stuff was screw-on freewheels.
Depends on the 7sp hub length+ 9sp freehub and if the bike is 135mm rear axel.
If the hub is longer than a 9sp hub you could get 5mm extra and open up the rear by 2.5 if its steel frame.
Best getting your tape meansure out and checking first.
I've done it - re-spacing is needed to get it back to 135mm.
Many 9s freehubs use different sealing arrangements so you may need the matching cone/locknut etc.
Bike is a newish Carerra Subway. Hubs are non branded (But surprisingly good quality and well sealed) Shimano-compatible ones. There's a lot of room either side of the cassette as it is, but there's definately no spacer behind the cassette.
If it's not a shimano hub I doubt it will work.
so you may need the matching cone/locknut etc.
I actually have 2 complete spare M475 hubs knocking about, so I have axles, cones, seal etc. No probs!
As above the freehub body will be different from Shimano, other wise yes it would have worked with a bit of respacing and a redish.
Edit, it's probably a Quando hub so you could in theory get another 8 spd freehub body but they are difficult to get hold of and lots of different fitting patterns.
If it's not a shimano hub I doubt it will work.
Why?
As I said in the OP, the only stumbling block is [i]"if a 9sp body fits the hub"[/i], so I'm already aware of that 🙂
Different companies attach the freehub to the hub in different ways, that's why - had presumed that your 7s was a shimano, as this is an obvious stumbling block.
I could just rebuild with an M475 hub I suppose, but where's the fun in that? 😉
If non-Shimano, then I'd be very surprised if the freehub is the same pattern, as Shimano kind of like their patents...
Still odd to hear of a 7-speed FH on a current bike. As I said; anything less than 8 usually involves a screw-on freewheel.
Sure there's not a spacer? Have a measure of the spline depth on the hub and the Shimano ones.