Derailleur capacity

Paul Boyd said:

Some opinions please (what, on this group? :-) )

On my MTB I have a 24/36 double on the front with an 11-32 cassette.
This gives a required derailleur capacity of 33T. The mech I have
has a capacity of 33T. All well and good.

I'm thinking about putting a 44T on the front to give a 24/36/44
triple. This means I theoretically need a mech with a capacity of
41T. BUT... isn't this only the case if I was going to use the
extremes of crossover, i.e., 44front/32rear or 24f/11r or
thereabouts? In other words, if I kept the short cage mech and
avoided the extreme chain angles (which I do anyway) will things
still work? I just wouldn't use the positions where the mech is
either pulled all the way forward or relaxed all the way back.

It will work until your brain disengages, and you try to shift to an illegal
gear. Then you may regret it. Might work OK if its only the two extremely
crossed over gears.

My tourer has one illegal gear, big rear to big front. But I've always
avoided that combination on every bike I've owned, so it doesn't catch me
out. Small to small is permitted (though only used when brain fails).

I've had a tighter arrangement on my station hack bike (couple of gear at
each end of the range were illegal). I got fed up with graunches and near
calamities by forgetful shifting. I gave in and bought a cheap long cage
rear mech.

- Nigel

--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

in message <[email hidden]>, Paul Boyd

(') said:

Some opinions please (what, on this group? :-) )

On my MTB I have a 24/36 double on the front with an 11-32 cassette.
This gives a required derailleur capacity of 33T. The mech I have has a
capacity of 33T. All well and good.

I'm thinking about putting a 44T on the front to give a 24/36/44 triple.
This means I theoretically need a mech with a capacity of 41T. BUT...
isn't this only the case if I was going to use the extremes of
crossover, i.e., 44front/32rear or 24f/11r or thereabouts? In other
words, if I kept the short cage mech and avoided the extreme chain
angles (which I do anyway) will things still work? I just wouldn't use
the positions where the mech is either pulled all the way forward or
relaxed all the way back.

I would not recommend this. You only have to accidentally go into big/big
once (and let's face it we've all done it) and you'll write off your
derailleur, your derailleur hanger, and possibly your frame. Not worth the
risk.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

<p>Schroedinger's cat is <blink><strong>NOT</strong></blink> dead.</p>

Thanks both. I think "it will work but isn't worth the risk" is the
summary there. As the reason for having a short mech is to slightly
reduce the risk of it being smacked against a rock I won't risk it in a
different manner - I'll either stick with a double on the front or go
for a long cage mech (which I just happen to have spare, as you do)

The frame this will be going on is an Orange P7, and there is no way I
want to risk that!

--
Paul Boyd
http://www.paul-boyd.co.uk/

Simon Brooke said:

in message <[email hidden]>, Paul Boyd

(') said:

Some opinions please (what, on this group? :-) )

On my MTB I have a 24/36 double on the front with an 11-32 cassette.
This gives a required derailleur capacity of 33T. The mech I have
has a capacity of 33T. All well and good.

I'm thinking about putting a 44T on the front to give a 24/36/44
triple. This means I theoretically need a mech with a capacity of
41T. BUT... isn't this only the case if I was going to use the
extremes of crossover, i.e., 44front/32rear or 24f/11r or
thereabouts? In other words, if I kept the short cage mech and
avoided the extreme chain angles (which I do anyway) will things
still work? I just wouldn't use the positions where the mech is
either pulled all the way forward or relaxed all the way back.

You can push a mech's capacity a bit. I think by 8 teeth would be too much,
though. You'd have to avoid more than just the extremes anyway.

Quoted message said:

I would not recommend this. You only have to accidentally go into
big/big once (and let's face it we've all done it) and you'll write
off your derailleur, your derailleur hanger, and possibly your frame.
Not worth the risk.

That's a danger if the chain was too short for the big-big. I don't think
such terrible things would happen otherwise.

~PB

Pete Biggs said the following on 22/04/2007 21:52:

Quoted message said:

You can push a mech's capacity a bit. I think by 8 teeth would be too much,
though. You'd have to avoid more than just the extremes anyway.

Yes - the way I ride is to normally sit in the middle ring, and just use
the big ring with the smallest 2 or 3 cogs, and the small ring with just
the biggest 2 or 3. Usually.

Quoted message said:

That's a danger if the chain was too short for the big-big. I don't think
such terrible things would happen otherwise.

The chain would be the right length.

When the new frame arrives, I think I'll just try it with it up on the
stand. If I have any doubts though, I'll play safe.

--
Paul Boyd
http://www.paul-boyd.co.uk/

in message <[email hidden]>, Pete Biggs

(') said:

Simon Brooke wrote:

Quoted message said:

Quoted message said:

I would not recommend this. You only have to accidentally go into
big/big once (and let's face it we've all done it) and you'll write
off your derailleur, your derailleur hanger, and possibly your frame.
Not worth the risk.

That's a danger if the chain was too short for the big-big. I don't
think such terrible things would happen otherwise.

Yup. But if you don't have enough take-up in your derailleur cage, then
either it's too short for big-big or it's massively too long for
small-small. Which I grant you, is less of a problem - there was a fashion
in France between the wars for riding with a very loose chain.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

The Conservative Party is now dead. The corpse may still be
twitching, but resurrection is not an option - unless Satan
chucks them out of Hell as too objectionable even for him.

Paul Boyd usenet.dont.work@plusnet said:

Pete Biggs said the following on 22/04/2007 21:52:

Quoted message said:

You can push a mech's capacity a bit. I think by 8 teeth would be too much,
though. You'd have to avoid more than just the extremes anyway.

Yes - the way I ride is to normally sit in the middle ring, and just use
the big ring with the smallest 2 or 3 cogs, and the small ring with just
the biggest 2 or 3. Usually.

thats genurally what i do, though with my mountain bike. though i try to
predict what's coming so i'm in the right ring.

on the road bike (old mountain bike with marthons) i tend to hold it in
the top ring as it zips about well and kingston upon thames area pritty
much flat.

snips

roger