Bicycle Mechanics - When to replace chain and sprocket

Hi Guys,

For mountain biking, or any riding where your chain is exposed to dirt, sand etc, how do you know when to replace the chain? I've heard 2 theories:

1. Wait until the chain is slipping off the sprocket and then replace both the chain and sprocket. The chain wears to that sprocket.

2. Replace the chain frequently and have a sprocket that last a whole lot longer.

Both ideas make sense and it almost seems like personal perference. I'm temped to go with the 2nd as my sprocket appears to be in descent condition--the non-shifting teeth don't have rounded edges. How do you know when it's time to replace the chain? Currently mine seems to have a bit of lateral flexibility, which I've heard is a sign. Also, what advantages are there of more expensive chains than cheaper ones? As far as I know, the chain it's job as long as it isn't slipping off or breaking. It seems like it would be better to buy inexpensive chains and replace them frequently.

Thank you for the help.

#2 option is the best and only way to go. Buy a tool from Park (chain gauge) that measures stretch or wear on the chain.

If you replace your chain before it is excessively worn (ya need to get a tool to measure) then you can get several chains out of your cassette.

chains are fairly inexpensive compared to the cassette and c rings. Have seen many people that will run a chain well after its worn and end up wearing out the drive train completely needing new chain, cass and c-rings which is a very expensive.

Actually, you don' t need a tool. You can measure chain wear easily with a good ruler.

I prefer a tool because with my presbyopia I have trouble reading the ruler. http://www.thesmilies.com/smilies/mad0197.gif

Hi Guys!

Thanks for the replies.

Well I stopped by the local bike shop and asked the guy to check out my chain (don't have one of the tools). It checked out ok as far as stretch goes--the tool would not go down in-between the links, which I'm assuming indicates that you still have some chain life left. For now this one's going back on. I'm going to invest in one of those tools and change it the moment the tool indicates. Also it would be nice to make the cassette last as long as possible for the pain it takes to change it as much as what it costs. Last time I changed the chain, I changed the cassette with it and paid $20 for each component.

What are the advantages of having more expensive chains? It should be durable, minimal wear rate and resistant to breaking--but other than that, it seems pointless to spend $50 or more.

Hi Guys!

I'm going to invest in one of those tools and change it the moment the tool indicates.

What are the advantages of having more expensive chains? It should be durable, minimal wear rate and resistant to breaking--but other than that, it seems pointless to spend $50 or more.

No need to buy a gauge. You can measure "stretch", see: http://www.sheldonbrown.com/chains.html
I admit I do use the Park gauge and it's a quick go/no-go check. I find that the more convenient a tool is, the more I am likely to use it. I do check my chain about once every two months, and historically, I replace my chain once a year.

One of the benefits of a more expensive chain is bragging rights. For most riders, a middle of the road chain (like the SRAM PC971, ~$25) is just fine.

better to change chain often, like changing oil in your car
safer than fixing engine

I change the chain often, and recently changed the cassette after running it for 12,000+ miles -- it just started slipping. Can't believe how much more smoothly the bike runs and shifts.. Next time I will change the cassette after half that mileage.

But, to answer the question, replace the chain at conservative intervals and get more miles out of the cassette.

The other alternative is to rotate chains. The problem is the chain wears faster than the sprockets. If you know by how much you can rotate several chains so the chain wears at approximately the same speed as the sprockets.

For example if you normally use three chains per cassette you buy three chains and rotate them periodically. The overall chain wear will be the same but distributed over three chains.

The advantages are that you don't have to measure for stretch and you have lots of time to clean and lube the dirty chain before it is required again.
The disadvantage is the up front cost and remembering to rotate the chains.

Hm... That's an interesting thought. One thing I'm not sure about is if I should wait until the chain reaches the state of being "stretched" by standard of the chain gauge, or go ahead and get a new chain. I certainly don't want to get rid of a chain that still has life. However, I dislike the fact that the spocket increases it's effective spacing between teeth to match the chain. Currently I still have one chain that is not yet "stretched," but pehaps I should go ahead and get a new chain while the sprocket is still able to acept on. Otherwise, I would only be able to use the current sprocket with the current chain and have to replace both of them later.

Cycling chains could be the answer. I think it's a pretty dumb suggestion to sacrifice several chains to one single sprocket, discarding the only partly-worn ones and forgetting that chains cost money just like the sprockets (no offense intended towards anyone). Now, the question is (slightly long-term) when should one stop buying new chains and start the old group of chains on their 2ndary usage, tertiary usage etc?