Bicycle Mechanics - Excessive cog wear after only 900 miles?

Last night I changed the chain on a new bike I bought in May. I've only put 900 miles on it. This morning with the new chain on, I got some pretty extreme chain slippage while in the two rear cogs I use the most. There's no stiff link on the new chain, and everything was working just dandy prior to changing the chain.

Is it possible that I have that much wear on my cogs after only 900 miles? The old chain did have some stretch on it, but only 1/16 to 1/8 inch.

That is a lot of stretch, actually.

Are you sure you have the same number of links on the new chain?

Are you sure you have the right chain?

You might clean and lube and adjust the derailleur to see if you can improve it.

You might also ride it for a little bit to see if the chain/cog marry better.

But it sounds like you need a new cassette. Many people change chain/cassette together as a matter of habit. I would have hoped that 900 miles would not have required this, but with that kind of stretch, I think that is what you are looking at.

jim

If the old chain was that badly "stretched" it could have worn the most-used cogs pretty quickly.

If the old chain was that badly "stretched" it could have worn the most-used cogs pretty quickly.
exactly. when a cassette is worn enough to warrant replacing, it's usually worth replacing the chain at that time too.

edit: sorry, I missed the part where you said "new bike" so the chain was new, too. I was thinking the chain was old (and probably already stretched) and the cassette was replaced 900 miles ago.

900 miles seems like too quick a lifespan for a chain let alone a cassette. Any ideas on why the chain would have excessive gap between pins in only 900 miles?

Yikes. I never thought that 900 miles would damage my drive train so badly. Who the heck are these people I see on BF who say they go 4000 miles or more without changing the chain?

So, if I replace the cassette, am I going to have to change the chain more frequently in the future? I thought I was cleaning and lubing the chain fairly regularly. Wipe down and lube at least weekly, more thorough cleaning with a degreaser at least monthly.

900 miles seems like too quick a lifespan for a chain let alone a cassette. Any ideas on why the chain would have excessive gap between pins in only 900 miles?

I don't know why.

Every time I've replaced a chain on other bikes, I've seen similar stretch, but I don't know how many miles they had on them. (The new bike I bought in May was the first one that I've used a computer with.) Even with similar stretch on other chains, I haven't had the kind of slipping that I'm experiencing with the new bike.

And just so we're clear, the 1/16 to 1/8 inch stretch is over the entire 112 link chain.

And just so we're clear, the 1/16 to 1/8 inch stretch is over the entire 112 link chain.

The entire chain is 56.125"? or are you saying that you got the same excess 1/8" over various 12 sections around the chain?

And just so we're clear, the 1/16 to 1/8 inch stretch is over the entire 112 link chain.
OK, that isn't very much. Normally chain elongation is reported over a 12" (24 half-links) section and 1/8" is way too much. If you chain is elongated only 1/8" over its entire length then either the cogs were defective or something else is going on.

If your two "worn" cogs are in the middle of the cassette, check to see if your cable is stretched. Often missed shifts and noise from mid range gears are di to cable stretch. 900 miles is right for cable stretch but not chain stretch to the point where gears are worn

If your two "worn" cogs are in the middle of the cassette, check to see if your cable is stretched. Often missed shifts and noise from mid range gears are di to cable stretch. 900 miles is right for cable stretch but not chain stretch to the point where gears are worn

Indeed they are in the middle of the cassette. I'll give that a look. Thanks.

The entire chain is 56.125"? or are you saying that you got the same excess 1/8" over various 12 sections around the chain?

I'm saying that the entire chain is 56.125".

I'm saying that the entire chain is 56.125".

Ahh OK, that is not unreasonable wear after 900 miles. I would not have replaced it.

But, that is no longer the issue. You have two gears that slip. I think Stan's suggestion is the proper next step.

Chains and cassettes wear. It's a fact that can only be avoided by not riding the bike. The key is to minimize it by keeping the chain clean and well lubricated and that's a topic the forum search function will provide you enough opinion on to prevent chain wear forever (cuz you will read til you die and therefore not be riding your bike and wearing things out). If it's clean, lubricated and adjusted properly it will all last longer and run and shift smoothly. My current chain is approaching 3000 miles. My chain wear indicator shows less than 0.75% wear and it runs and shifts smooth and quiet, but at a price - regular care and maintenance (read - kept clean, lubricated and adjusted).

If the teeth on the cogs are not worn to sharp points, then try to adjust the shifter cable with the adjustment screw.

I use cheap chains and only get about 500 miles before they need replacing. I get 1/16" wear over a 12" section of chain.

The key is to minimize it by keeping the chain clean and well lubricated and that's a topic the forum search function will provide you enough opinion on to prevent chain wear forever (cuz you will read til you die and therefore not be riding your bike and wearing things out).

Yes! Not that I want to start trouble, but if you want to hear an argument in a bike shop, just ask what the best way to clean a chain is. Or, state authoritatively that one oil/wax/lube is the best!

Very funny!

If the teeth on the cogs are not worn to sharp points, then try to adjust the shifter cable with the adjustment screw.


Forgive me for asking a stupid question... Is this to increase the overall tension on the chain?

(I'm an ignoramus about bike maintenance, but I'm learning... slowly.)