8 Speed/9 Speed mixture on MTB



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Candt

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Without wanting to incur the wrath of the newsgroup purists (you know who you are), I need to ask a
technical question, but one specific to MTB's, so I'm asking here rather than rec.bicycles.tech...

I had an 8 speed bike... STX 8 speed shifters, 8 speed cassette... I was recently talked into buying
an XT front mech by my wife (her brother was working in the shop, and told me I had to buy something
to make him look good - how cool is that!!)

Now, because the XT mech was incompatible with my crappy chainrings (24-34-42), I bought a set of
deore hollowtech 22-32-44 9-speed rings with cranks, and of course - the essential XT rear mech
too.... (This shop had 35% off a bunch of shimano stuff - so it was a great price)

Now, I'm quite good at setting up gearing, and I bought a new BB to improve the chainline which was
too wide at the front with the lower profile cranks, and am basically there, all gears can be
shifted into. The trouble is - the chain just about rubs on the front derailleur on one side of the
other. ie Lets say your in the middle chainring, if the chain is just touching one side on the 1st
cassette cog, I can tighten the cable so its not, but then it will touch on the 8th cog...

Now I know a 9 speed cassette would be preferable, and matching shifters too - but I've already
spent the budget on these other parts, and I thought that a 9 speed cassette is the same high to low
width than 8 speed, its just the spacing which is different. So - the only thing I can think of is
that the chain is too thick...

So in my usual round about way - all I need to know is - will a 9-speed chain help? Is it indeed
thinner, as I only need to save about 1mm to prevent the rubbing? and will a 9-speed chain work with
an 8-speed cassette?

Cheers then

CandT
 
CandT <[email protected]> wrote

> Now, because the XT mech was incompatible with my crappy chainrings (24-34-42), I bought a set of
> deore hollowtech 22-32-44 9-speed rings with cranks, and of course - the essential XT rear mech
> too.... (This shop had 35% off a bunch of shimano stuff - so it was a great price)
>
> Now, I'm quite good at setting up gearing, and I bought a new BB to improve the chainline which
> was too wide at the front with the lower profile cranks, and am basically there, all gears can be
> shifted into. The trouble is - the chain just about rubs on the front derailleur on one side of
> the other. ie Lets say your in the middle chainring, if the chain is just touching one side on the
> 1st cassette cog, I can tighten the cable so its not, but then it will touch on the 8th cog...

I have never been able to adjust my front mech on an 8-speed system so using the middle ring, that
it reaches all 8 rear cogs without rubbing. I set it up so that I can easily get the smallest 4-5
cogs with the big ring, all but the smallest cog with the middle ring (want to avoid using the
smallest cog as it will wear out so quickly) and the largest 4-5 cogs on the small ring.

You could try to spread out the cage of the front mech a bit, I suppose, but I'd be happy with what
you've already achieved.

I don't think a narrower 9-speed chain is a good idea. It probably won't work well on an 8-speed
cassette (but I haven't tried it) and it will wear out more quickly.

-Myra
 
[email protected] (Myra VanInwegen) wrote
> I have never been able to adjust my front mech on an 8-speed system so using the middle ring, that
> it reaches all 8 rear cogs without rubbing.

<snip>

Same here. When I got the bike it was fine, but when I had to replace my front mech cable it went to
pot. Even the bike shop couldn't fix
it. I can have no-rub on most combinations, but rub on others, or visa-versa. I'm taking a
large pair of pliers to it when I can be bothered - anything Shimano can do, I can do with
a mole wrench!
 
stephen pridgeon <[email protected]> wrote in message
news:[email protected]...
> [email protected] (Myra VanInwegen) wrote
> > I have never been able to adjust my front mech on an 8-speed system so using the middle ring,
> > that it reaches all 8 rear cogs without rubbing.
>
> <snip>
>
> Same here. When I got the bike it was fine, but when I had to replace my front mech cable it went
> to pot. Even the bike shop couldn't fix
> it. I can have no-rub on most combinations, but rub on others, or visa-versa. I'm taking a large
> pair of pliers to it when I can be bothered - anything Shimano can do, I can do with a mole
> wrench!

IME it's a sure sign that the mech is wearing - I've had this a few times now (I'm just about to put
my 4th front mech on my mtb) and every time I can set it up perfectly with a new mech but not with
the old one. If you try wiggling the mech cage you can see the wear fro yourself - there shouldn't
be any movement.

Anyone know if XTR has more adjustment than XT ? I'm thinking I might be able to delay the
onset that way.

Russ
 
"Russell Pinder" <[email protected]> wrote in message
news:[email protected]...
>
> stephen pridgeon <[email protected]> wrote in message
> news:[email protected]...
> > [email protected] (Myra VanInwegen) wrote
> > > I have never been able to adjust my front mech on an 8-speed system
so
> > > using the middle ring, that it reaches all 8 rear cogs without rubbing.
> >
> > <snip>
> >
> > Same here. When I got the bike it was fine, but when I had to
replace
> > my front mech cable it went to pot. Even the bike shop couldn't fix
> > it. I can have no-rub on most combinations, but rub on others, or visa-versa. I'm taking a
> > large pair of pliers to it when I can be bothered - anything Shimano can do, I can do with
> > a mole wrench!
>
> IME it's a sure sign that the mech is wearing - I've had this a few
times
> now (I'm just about to put my 4th front mech on my mtb) and every time
I can
> set it up perfectly with a new mech but not with the old one. If you
try
> wiggling the mech cage you can see the wear fro yourself - there
shouldn't
> be any movement.
>
> Anyone know if XTR has more adjustment than XT ? I'm thinking I might
be
> able to delay the onset that way.
>

I binned one XTR mech trying to solve that problem (among others) and concluded (along with several
bike shops) that it is a characteristic of the beast. In short, XTR does it too - and from fresh out
of the box.

Of course if the BB and hubs are using rubble for bearings a certain loss of precision in the drive
train is inevitable.

Peter
 
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