Chain lenght

[simmi]

I am going to change my 9 speed cassette from a 12-23 to a 12-27.
Obviously the chain path on the lowest cog will be the same but on the highest I have calculated it will be about 1" longer.
Will I need to add an extra link to my chain or will I get away with it?

 

[Rickshaw Phil]

It's best to use a new chain when fitting a new cassette (old chain on a new cassette will accelerate the wear on the cassette).

The usual method of judging the length of new chain is to wrap it round the biggest chain ring and the biggest sprocket without running it through the derailleurs. That length + 2 links is the length needed.

 

[slowmotion]

Smokin Joe (of this parish) posted a link to this chain length calculator back in 2008.
http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html
There are other ones online too, eg...
http://www.epicidiot.com/sports/chain_length_calculator.htm

The Shimano techdocs web pages give advice on how the cage should be oriented when the chain is the correct length.

 

[Rickshaw Phil]

I don't like that 2nd one. They show 2 links and state that represents one link (don't know about everyone else but the last chain I bought was described as 116 links not 58). Great way to confuse newcomers.

Edit, the other does the same thing.