7/8/9 speed upgrading on MTB



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J

James Annan

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Time to update an old bike drivetrain, for various reasons.

The bike is about 6 years old with 135mm rear spacing and a shimano freehub. It was actually
previously equipped with a 7 speed shimano cassette using campag 8 speed ergo shifters and rear
derailler, which is a perfect match (5mm per shift). Back in those days I thought I knew about the
compatibility of the different options...but that was before 9 speed (before _I_ was interested in 9
speed, at least).

I'm now trying to put on a new 9 speed gripshift system. A 9 speed cassette doesn't seem to fit on
the hub but I can put on 8 of the cogs (actually the biggest 7 from a 9-speed cassette and then a
12T with lockring from an old 8). I've got new gripshifters and a matching rear derailleur (I've
been told the front shimano derailleur should work ok with non-indexed shifting, it can be changed
later if it causes trouble).

AIUI this ought to work fine as it's only the last 12-14 jump which may be fractionally incorrect.
I'm not really all that fussed about the 9th gear, since (a) it's only an 11T for a non-racing and
non-road-riding MTB which already sports a 50T front chainring (b) it's not my bike! But if I did
want to change to a full 9 speed, would it be difficult? Obviously it needs a few freehub, and maybe
respacing the axle, or is this not necessary?

Thanks,

James
 
R

Russell Pinder

Guest
James Annan <[email protected]> wrote in message
news:[email protected]...
> Time to update an old bike drivetrain, for various reasons.
>
> The bike is about 6 years old with 135mm rear spacing and a shimano freehub. It was actually
> previously equipped with a 7 speed shimano cassette using campag 8 speed ergo shifters and rear
> derailler, which is a perfect match (5mm per shift). Back in those days I thought I knew about the
> compatibility of the different options...but that was before 9 speed (before _I_ was interested in
> 9 speed, at least).
>
> I'm now trying to put on a new 9 speed gripshift system. A 9 speed cassette doesn't seem to fit on
> the hub but I can put on 8 of the cogs (actually the biggest 7 from a 9-speed cassette and then a
> 12T with lockring from an old 8). I've got new gripshifters and a matching rear derailleur (I've
> been told the front shimano derailleur should work ok with non-indexed shifting, it can be changed
> later if it causes trouble).
>
> AIUI this ought to work fine as it's only the last 12-14 jump which may be fractionally incorrect.
> I'm not really all that fussed about the 9th gear, since (a) it's only an 11T for a non-racing and
> non-road-riding MTB which already sports a 50T front chainring (b) it's not my bike! But if I did
> want to change to a full 9 speed, would it be difficult? Obviously it needs a few freehub, and
> maybe respacing the axle, or is this not necessary?
>

A new wheel (hub) is required I'm afraid - the hub is different for 8 & 9 speed as opposed to 7
speed, no respacing however - an 8 speed cassette is spaced the same as a 7 speed and is therefore
wider by 1 ring - a 9 speed cassette is the same width as an 8 speed but with closer spacings. 8 and
9 speed hubs are the same.

You might have fun with running the narrow 9 speed chain on an 8 speed 12T ring - I suspect it'll
slip a bit but this may not be an issue.

Russ
 
E

Eddie Dubourg

Guest
"Russell Pinder" <[email protected]> wrote in message
> > AIUI this ought to work fine as it's only the last 12-14 jump which may be fractionally
> > incorrect. I'm not really all that fussed about the 9th gear, since (a) it's only an 11T for a
> > non-racing and non-road-riding MTB which already sports a 50T front chainring (b) it's not my
> > bike! But if I did want to change to a full 9 speed, would it be difficult? Obviously it needs a
> > few freehub, and maybe respacing the axle, or is this not necessary?
> >
> A new wheel (hub) is required I'm afraid - the hub is different for 8 & 9 speed as opposed to 7
> speed, no respacing however - an 8 speed cassette is spaced the same as a 7 speed and is therefore
> wider by 1 ring - a 9 speed cassette is the same width as an 8 speed but with closer spacings. 8
> and 9 speed hubs are the same.

I've just upgraded from 7-9 speed on my emptyb, and I was able to keep my rear hub, I just had my
wheel redished, and had to move the spacers on the axle (and a new freehub, natch) and it's
running fine. The axle now only fills about 2/3s of the drops, but with QRs I believe they don't
need to be fully there (see what Sheldon says about using this to enable him to build a fixer with
vertical dropouts)

Take it into your lbs and see if they can re-dish it.

E
 
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