Can worn rings cause chain lengthening?

zil

Well as the title says really. I know that a worn/lengthened chain can cause your cassette and rings to wear out, but can worn rings cause your chain to lengthen?

Personally I would have thought that as long as the rings and chain aren't skipping under load then worn rings shouldn't decrease the life of the chain but I was wondering if anyone knew for sure?

Civilian_Target

No, it causes skipping, the chain to hop in and out of the cogs of the cassette under pressure. I guess each skip decreases the chain life.

blorg

Apart from the skipping I believe it does also accelerate the chain wear, yes, until the new chain pitch matches your worn rings. Sheldon agrees:

Sheldon Brown wrote:

A new chain on a worn sprocket. Most of the driving is happening on the left side, where the chain first engages the sprocket. Due to the mismatch in pitch, the rollers in the part of the chain that is about to leave the sprocket is doing very little to push their teeth forward, instead, they are being forced upward by the slope of the teeth.

Since the teeth/rollers on our left are doing most of the work the load is concentrated on them.

In addition, as the roller follows its tooth around the sprocket it rolls up the "ramp," while under load. This promotes wear to the insides of the rollers and to the "bushings" they roll on. With a properly meshed chain, the roller only turns a tiny bit as it rolls onto and off of the chain.

Due to the pitch mismatch, the chain will not reliably mesh with the sprocket under load, and will tend to jump forward, skipping over the teeth.

Jack Bracken

If you have a worn ring, consider getting a new saddle.

[/terrible pun]