Joe wrote:
> ...I like the bike, it feels comfortable but the chain keeps
> falling off. I'm pretty sure the rear and front cogs are shot.
The chain "falling off" is generally a symptom of a mis-adjusted
derailer, not worn parts.
When worn-out sprockets are an issue, the usual symptom is the chain
jumping forward on hard pedaling in some gears, and sometimes slow
shifting.
See:
http://sheldonbrown.com/derailer-adjustment
> Is this worth fixing?
Almost certainly.
> Is it possible for a novice to replace these parts
> myself?
It is unlikely that any parts need to be replaced, on the basis of your
description of the problem.
Possibly relevant oilerplate:
Back in the old days, every tooth on a chainring was the same as every
other tooth on that ring.
Beginning in the 1980s, however, Shimano started experimenting with
different shaped teeth in different parts of the chainrings, with the
aim of improving shifting.
Newer chainrings typically have some teeth much shorter than others,
usually the teeth that are picking up the chain when the cranks are
vertical (this is when chain tension is lowest, and is the best time to
make the shift.
These special stubby teeth, often coupled with "shift assist" pins and
ramps on the side of the chainrings, make a great improvement in
shifting.
However, one drawback of this is that folks who aren't aware of this
design will sometimes discover the short teeth and will assume that
their chainrings are damaged or worn out! They aren't!
It is very rare to actually wear chainrings out, takes many, many
thousands of miles with a worn-out chain. When a chainring is worn
out, _all_ of the teeth show the wear, usually acquiring a hooked
appearance on the sides of the teeth that drive the chain.
For further information on this, see:
http://sheldonbrown.com/chains
Don't be embarrassed about this...this is a _very_ common question, so
common that I have prepared this generic boilerplate response to save
re-typing.
Sheldon "Adjustment" Brown
+--------------------------------------------------------+
| There is no conclusive evidence of life after death. |
| But there is no evidence of any sort against it. |
| Soon enough you will know, so why fret about it? |
| --Robert A. Heinlein |
+--------------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
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