New chain skips on _new_ cassette

Karl Nelson

I replaced my cassette and chain at the same time. The chain was an
old style with bushings and it skipped on the smaller sprockets, which
I attributed to it being pushed sideways by the ramps because it was
too wide. However, after about three miles I realized that it was
also skipping on the front chainring, which turned out to be very
worn.

Now with new chainrings and a narrower chain ("SRAM-PC58"), I get
skipping on the 13t sprocket. (Both the 15t and 11t seem OK but I have
ridden much yet.) Of the three miles ridden with the wider chain and
worn chainrings, less than 1/2 mile was probably on the 13t sprocket.
Most was probably on the 18t sprocket.

The narrower chain was ridden about 100 feet on the worn chainrings.
I do see wear from this, I think: 24 links measure about 24 1/32
inches.

I don't have the other chain in front of me to measure it.

Is it possible that the chainrings wore the chain which in turn wore
the cassette sprocket to the point where a new chain now skips on it,
all in 1/2 mile? Any other explanations? Anything I can do about it?

Also, does my thought for why the chain with bushings was skipping
seem right? It's called a 6/7-speed chain ("KMC-HP20"), on a 7-speed
HG cassette--it seems like it should have worked.

Thanks,
Karl Nelson.

Ron Hardin

I've had new chains skip on new freewheels (none of this high tech
stuff) and it stopped when the chain wore a little. That was
years ago though.

I'd be surprised if anything skipped on the chainring. The chain
tends to pop off when it skips there. It's winding on under tension
on the chainrings and so doesn't ride up on a tooth the way it does
on a worn cog. So skipping on the chainring is most likely an
optical illusion.

Stiff link is the usual explanation. The stiffness only have to
be stiff against the derailleur tension, not your pedalling tension.

A skip is caused by a hook in a worn cog, which lets the chain pull up
inside the hook, so the oncoming link doesn't clear the tip of the
next tooth (unless the chain isn't stretched); the chain then rides
on top of the teeth until the whole army gets to the top of the cog,
and then everything slips until a random link catches a bottom tooth.
A burr on a cog could conceivably cause the same sort of thing, I guess.
--
Ron Hardin
rhhardin@mindspring.com

On the internet, nobody knows you're a jerk.

Ron Hardin

Ron Hardin wrote:
> next tooth (unless the chain isn't stretched); the chain then rides

unless the chain is stretched

edit error
--
Ron Hardin
rhhardin@mindspring.com

On the internet, nobody knows you're a jerk.

nomisa

kdnelson@my-deja.com (Karl Nelson) wrote in message news:<69197042.0404260912.1272d692@posting.google.com>...
> I replaced my cassette and chain at the same time. The chain was an
> old style with bushings and it skipped on the smaller sprockets, which
> I attributed to it being pushed sideways by the ramps because it was
> too wide. However, after about three miles I realized that it was
> also skipping on the front chainring, which turned out to be very
> worn.
>
> Now with new chainrings and a narrower chain ("SRAM-PC58"), I get
> skipping on the 13t sprocket. (Both the 15t and 11t seem OK but I have
> ridden much yet.) Of the three miles ridden with the wider chain and
> worn chainrings, less than 1/2 mile was probably on the 13t sprocket.
> Most was probably on the 18t sprocket.
>
> The narrower chain was ridden about 100 feet on the worn chainrings.
> I do see wear from this, I think: 24 links measure about 24 1/32
> inches.
>
> I don't have the other chain in front of me to measure it.
>
> Is it possible that the chainrings wore the chain which in turn wore
> the cassette sprocket to the point where a new chain now skips on it,
> all in 1/2 mile? Any other explanations? Anything I can do about it?
>
> Also, does my thought for why the chain with bushings was skipping
> seem right? It's called a 6/7-speed chain ("KMC-HP20"), on a 7-speed
> HG cassette--it seems like it should have worked.
>
> Thanks,
> Karl Nelson.


I had same problem with new chain skipping on new cassette. Stiff
link was the culprit.

Backpedal with the bike in a stand and you can often see the problem
link as it comes off the cogs or pulleys. In my case, it was the one
I drove the replacement pin through. I suspect this is pretty common
- the pin presses the plates together too tightly. Just take a
flat-head screwdriver, stick it btw plates, and gently flex them so
they're looser. I had no problems afterwards. Hope this works for
you.

Nom