Chain slipping off freewheel after installing a new chain

(JBAfromNY) said:

Here's the situation:

I have a 7-speed indexing Suntour freewheel/triple front
drivetrain (not cassette; yes, it's an old bike). I just
replaced the chain (some flavor of Sedis, IIRC), after
many years, with a new SRAM PC 48. When I had the bike up
on the stand, it shifted perfectly with the new chain.
However, when I actually rode it, the chain slipped on the
3 middle cogs, .

I fiddled extensively with both the indexing adjustment and
the b-tension adjustment. This didn't help.

The chain length looks OK (no obvious slack in small-middle
combos; no trouble shifting to big-big combos).

The cogs from which the chain slips all show greater
wear than the cogs that work OK, leading me to think
that the freewheel is the likely culprit. Is this it, or
is there something else I should check out before going
on a parts hunt?

Pretty typical symptoms following replacement of a chain
that has been used far beyond acceptable wear. As a chain
wears the distance between pins increases beyond the 1/2
inch at which it started out. This increase subsequently
wears the rings and cogs, especially the cogs that are most
heavily used. A new chain will no longer register properly
in the worn cogs, this the slipping/shipping you're
experiencing.

If you still have the old chain, try measuring it. There
should be a pin exactly every half inch. If the 24th pin
falls more than 12 1/8 inches from the first, you
probably waited too long to replace it. I'm guessing
"after many years" of use you'll find it measures
noticeably more than that.

Good luck finding new cogs for your Suntour freewheel. ;-)

jeverett3<AT>earthlink<DOT>net
home.earthlink.net~jeverett3Open ↗

Quoted post said:

Originally posted by Jbafromny
Here's the situation:

I have a 7-speed indexing Suntour freewheel/triple front
drivetrain (not cassette; yes, it's an old bike). I just
replaced the chain (some flavor of Sedis, IIRC), after
many years, with a new SRAM PC 48. When I had the bike up
on the stand, it shifted perfectly with the new chain.
However, when I actually rode it, the chain slipped on the
3 middle cogs, .

I fiddled extensively with both the indexing adjustment and
the b-tension adjustment. This didn't help.

The chain length looks OK (no obvious slack in small-middle
combos; no trouble shifting to big-big combos).

The cogs from which the chain slips all show greater
wear than the cogs that work OK, leading me to think
that the freewheel is the likely culprit. Is this it, or
is there something else I should check out before going
on a parts hunt?

TIA, John

Yes, it sounds like new freewheel time.

<http://www.yellowjersey.org/stfw.html>

Yellow Jersey specializes in these things.
The tooth profile on your old cogs has worn so that when you put a good load on the chain it rides up and jumps.

A good article on chains that will help explain is on Sheldon Brown's site:

<http://sheldonbrown.com/chains.html>

[email hidden] (JBAfromNY) wrote in news:13f5f670.0405140713.5e103f23
@posting.google.com:

Quoted message said:

I have a 7-speed indexing Suntour freewheel/triple front
drivetrain (not cassette; yes, it's an old bike). I just
replaced the chain (some flavor of Sedis, IIRC), after
many years, with a new SRAM PC 48. When I had the bike up
on the stand, it shifted perfectly with the new chain.
However, when I actually rode it, the chain slipped on the
3 middle cogs, .

Sounds like the freewheel is worn out.

JBAfromNY said:

I have a 7-speed indexing Suntour freewheel/triple front
drivetrain (not cassette; yes, it's an old bike). I just
replaced the chain (some flavor of Sedis, IIRC), after
many years, with a new SRAM PC 48. When I had the bike up
on the stand, it shifted perfectly with the new chain.
However, when I actually rode it, the chain slipped on the
3 middle cogs, .

I fiddled extensively with both the indexing adjustment
and the b-tension adjustment. This didn't help.

The chain length looks OK (no obvious slack in small-
middle combos; no trouble shifting to big-big combos).

The cogs from which the chain slips all show greater
wear than the cogs that work OK, leading me to think
that the freewheel is the likely culprit. Is this it, or
is there something else I should check out before going
on a parts hunt?

Yes. Read this: draco.acs.uci.edu8d.2.htmlOpen ↗

and then maybe this: yellowjersey.orgstfw.htmlOpen ↗

--
Andrew Muzi www.yellowjersey.org Open every day since 1
April, 1971