[ryder]

I have an old 9 speed mountain bike with an extremely rusted chain, anybody have any suggestions as to what I should replace it with?

[CTD50]

A new 9-speed chain. (Sorry, just too obvious to pass up)

SRAM 951 will do you just fine. Chains are a 'wear-out item', so spending crazy money on them is just...well, crazy. The 951 is under $20.

[hophead]

Keep in mind that the cassette and chainrings wear together with the chain and should also be replaced. Sometimes you can just get away with replacing one or two of the chainrings. For instance, if you primarily use your middle ring, that one may be worn, but your big ring and granny may be fine. The cassette should always be replaced with the chain.

[Grape Ape]

Originally Posted by hophead

Keep in mind that the cassette and chainrings wear together with the chain and should also be replaced. Sometimes you can just get away with replacing one or two of the chainrings. For instance, if you primarily use your middle ring, that one may be worn, but your big ring and granny may be fine. The cassette should always be replaced with the chain.

I have seen this mentioned many times. What if the chain is not worn out due to use. The OP mentioned rust. What if the chain is bad due to rust from the bike setting around and not worn out due to use. If the chainrings and cassette are not worn and not rusted should they be left as is and just replace the chain?

[hophead]

Originally Posted by Grape Ape

I have seen this mentioned many times. What if the chain is not worn out due to use. The OP mentioned rust. What if the chain is bad due to rust from the bike setting around and not worn out due to use. If the chainrings and cassette are not worn and not rusted should they be left as is and just replace the chain?

"Old and extremely rusted" to me means that most likely it's gonna need more than just a chain. I suppose if the bike was not ridden much, it's possible that the cassette is ok. 9 speed drive trains aren't very forgiving though. To insure that it shifts properly, I would at least replace the cassette and inspect chainrings and replace those as necessary.

[froze]

I'm weird, but here it goes anyways. I get about 12 to 15,000 miles on a chain, I replace the chain but I don't replace the cassette because it's not worn. I can get 30,000 on a cassette, so this means I'm replacing the cassette every other time not every time. And even when I do replace the cassette it was still shifting just fine. I use the Park chain wear tool cc-2c I just bought...niffty but a ruler works too.

[wild]

Here is my .02 if the chain is rusted, the rust is hard and will act like a file on the cassette and chain rings, I guess you could clean it but a new chain is the better way to go. My .02

[maxjasper]

Extreme rusted chain means bike has been left in a west place, under rain, etc. for a long time. Not only the chain can not be trusted but even all parts of the bike should be properly inspected and lubricated before any riding.