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 http://home.earthlink.net/~jeverett3

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?
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:
http://draco.acs.uci.edu/rbfaq/FAQ/8d.2.html

and then maybe this:
http://www.yellowjersey.org/stfw.html

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