chain jumping off sprockets problem

RB said:

I don't know zilch about bikes. My wife wanted to start riding around the
neighborhood for exercise, so bought a bike. Also, with gas prices going
sky high, it'll save us a few coins on short hauls.

It's a Hermosa Huffy, and has 5 gear type sprockets.

For some reason, the chain comes off everytime we turn around. I figure
there's some simple adjustment or something maybe I can do to help stop that
from happening.

Thoughts and suggestions solicited.

Dear RB,

If you have a single front sprocket at the pedals and 5
gears at the axle . . .

And the chain comes off when you shift to the smallest (or
largest) rear gear . . .

Then you can probably fix things by turning a screw:

http://www.sheldonbrown.com/derailer-adjustment.html

The link is explains things, with pictures.

A pair of small screws on the derailleur limit how far the
derailleur can move toward the large and small gears.

They're nothing fancy, just screws that the arms of the
derailleur physically bump into.

If they're sticking out far enough, the derailleur movement
is limited, so it can't drag the chain past the last gear.

One screw limits how close the derailleur can get to the
spokes, while the other screw limits how close it can get to
the rear frame tubes.

If this isn't what's wrong, you'll probably have to explain
the problem in more detail--

When does the chain come off? (During shifting, when you
bumps in the road, as soon as you push on the pedals?)

Where does it come off? (Front sprocket? Small rear gear?
Large rear gear?)

Carl Fogel

RB said:

For some reason, the chain comes off everytime we turn around.

1. From the front or rear? How many sprockets on the front? I'm guessing
the rear has 5?
2. Do you mean 'turn around' as 'often' or when you reverse the bike's
heading?
3. What are you doing just as the chain comes off?
4. What is the condition of the chain/sprockets? Rust? Stiff links?

On Mon, 5 Sep 2005 21:03:37 -0500, "RB" <[email hidden]>

Quoted message said:

I don't know zilch about bikes. My wife wanted to start riding around the
neighborhood for exercise, so bought a bike. Also, with gas prices going
sky high, it'll save us a few coins on short hauls.

It's a Hermosa Huffy, and has 5 gear type sprockets.

For some reason, the chain comes off everytime we turn around. I figure
there's some simple adjustment or something maybe I can do to help stop that
from happening.

Thoughts and suggestions solicited.

As others will no doubt be quick to point out, Huffy's bikes are not
exactly the cream of the crop. (More like the stale moldy imitation
cheese of the crop, in fact.)

That aside, if the chain is jumping off, there are usually a limited
number of probable causes. Given that the Hermosa is most often sold
at Wal-Mart, and that the assembly skill applied to their bikes is
wildly variable, my first suspicion is that the derailleur adjustments
are out of whack. There's a basic primer on how to adjust the ders at

http://sheldonbrown.com/derailer-adjustment.html

which is a good place to start. There's also a possibility that the
chain is stiff from not being properly lubricated; oiling the chain
would probably address that issue. If the chain's jumping has become
worse with successive rides, and if it got jammed between the frame
and the rest of the components at some point, you may have some bent
bits contributing to the misbehavior, possibly including the chain
itself.

All of these issues can be addressed, and it's my opinion that with a
little patience and some fiddling with the adjustments, you'll
probably be able to get the Huffy to shift reliably...but bear in mind
that with this type of setup, it's wise to remember these points:

-- Never try to shift when you are not pedalling, regardless of
whether the bike is moving.

-- Avoid moving the shifter through more than one gear click at a
time; let the chain make one sprocket change before asking it to move
to another.

-- Change gears when pedalling, but NOT when pedalling while
standing up. The shifting system will work best when the gear change
occurs with the chain not under heavy load.

Hope that helps.
--
Typoes are a feature, not a bug.
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Thanks. Good web site. Gave me the info I needed to fix the problem.