Chain length?

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

Hello,

How do you tell how long the chain should be? The chain on my
mother-in-law's bike looks like it is too long because the rear
derailer pulley rides on the the low gear. I took a couple of links
out and then it was too short, it wouldn't shift to all the gears. How
do you tell if it has the right derailer?

If any of the drive train is not the same spec as the original, it may
be impossible to get it to work. Changing the cogs, chainrings or
derailleur may give you a combination in which it's impossible to make
all gears work.

However, you might look into getting a mountain bike derailleur, such as
a Deore. They have a very long cage, which will allow you to use a
chain long enough to handle the big/big combination, and still take up
all the slack in the small/small combination.

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Chris Hansen said:

How do you tell how long the chain should be?

Most common method, which works 95% of the time, is : wrap chain around
big/big sprockets without derailleur, add one link.

Chris Hansen said:

How do you tell how long the chain should be? The chain on my
mother-in-law's bike looks like it is too long because the rear
derailer pulley rides on the the low gear. I took a couple of links
out and then it was too short, it wouldn't shift to all the gears. How
do you tell if it has the right derailer?

See:
http://www.sheldonbrown.com/derailer-adjustment.html#chain

But the problem may be a "B-Tension" screw misadjustment on the rear
derailleur.

See:
http://www.sheldonbrown.com/gloss_ba-n.html#btension

Art Harris