Starting road biking, need some repair/maintenance knowledge

[Tokay]

I've recently picked up road biking, after having grown up riding
mountain biking. Let me say first that road bikes are surprisingly
unstable by comparison, but also lightning fast!

Anyway, looking for a commuter bike, I came across a $10 ten-speed
junker in a local thrift shop. I've been tuning it up and it's
*almost* in perfect working order.

Other than trying to get used to friction shifters instead of indexed,
It's only got two issues left, now.

One is wheel truing, they're just a tad off. (don't worry, I know how
to true a wheel)

The other is the one I need help with.
The chain slips when I'm putting a lot of power to the wheels, mostly
in higher gears.

I'm not expert bike tech, so I'm not sure what causes this. The cogs
look almost perfect, and chainrings look good, but the rear derailleur
cogs look fairly worn. Is this the source of the problem? The chain
is also in good shape, so I just don't know what it would be...

Also, has anyone here heard of Aurora Custom? That's what's branded on
the bike, but I've never heard of it, and neither has Google.

 

[Arthur Harris]

"Tokay" wrote:

> The other is the one I need help with.
> The chain slips when I'm putting a lot of power to the wheels, mostly
> in higher gears.
>
> I'm not expert bike tech, so I'm not sure what causes this. The cogs
> look almost perfect, and chainrings look good, but the rear derailleur
> cogs look fairly worn. Is this the source of the problem? The chain
> is also in good shape, so I just don't know what it would be...

What you describe is the classic symptom of a new chain on a worn cassette
or freewheel. The skipping may only occur on the most worn cogs. The jockey
and tension wheels of the derailleur are not the problem.

Art Harris

 

[Dan Lenski]

Are you sure the chain's not worn? By rear derailleur cogs do you mean
the freewheel/cassette (the set of 5 gears attached to the back wheel)?

If those are worn, it will cause the chain to skip. The high gears are
most likely to skip because they have fewer teeth to bear the load and
tend to wear out faster. A new 5 or 6 speed freewheel is cheap these
days and easy to replace.

 

[Tokay]

I was under the impression that lower gears wore out first, due to the
torque involved....
The teeth aren't all chewed up, so what are the signs of wear?

 

[Dan Lenski]

I think it may be a question of definition. A "gear" on a bike isn't a
physical object, it's a particular combination of chainring (front
sprocket) and cog (back sprocket), at least on a derailer-geared bike.

The sprockets with fewer teeth tend to wear out faster than the
sprockets with more teeth (assuming equal use), because the sprockets
with fewer teeth distribute the load over fewer teeth.

It is very difficult to visually identify a worn sprocket. Identifying
a worn chain is easy, you just need to measure it with a ruler. It
does sound like your problem is the combination of a new chain with
worn sprockets. For more details, read this page:
http://www.sheldonbrown.com/chains.html , specifically the section on
"Chain and Sprocket Wear."