New Cassette & Chain length?

[Carbon]

Hello all!

I currently have a 12 - 25 cassette, I have just treated myself to some new wheels and am looking at a new cassette to go with them, got my eye on a nice Dura Ace 11 - 23.

Question is will I be O.K with the existing chain without shortening it or because it's a slightly smaller cassette should the chain be shortened? (It's a Shimano HG chain so is compatible with the Dura Ace cassette).

I'm thinking the rear derailleur should cope with the new cassette without adjustments to the chain length but I've been wrong in the past!

Any advice appreciated.

Thanks.

 

[RecordAceFromNew]

Assuming the chain was of the correct length then you will likely want to shorten it by 1 link. In case it wasn't and to establish the collect length see:
http://bicycletutor.com/calculate-chain-length/

 

[HLaB]

I've asked a similar question in the past and was told it makes no difference and they were right.

 

[andrew_s]

The new cassette having 2 teeth fewer means that the chain ought to be shortened by 1 link (0.5").
However you can only shorten chains in pairs of links (1"), so it's only possible if the chain is currently slightly long.

Check the chain stretch. If 24 links measures much more than 12 1/16" you'll want a new chain, in which case you should size the chain from scratch rather than just copy the old one.

 

[Carbon]

Thanks all.

The existing chain only has 300 miles on it and is spot on for length, no stretch yet.

So looking at what you're saying I should be O.K with the existing chain because removing two links would likely make it to short!

I guess the proof of the pudding will be in the eating.

 

[Paulus]

The tension in the rear mech should take up the small amount of slack there may be in the chain.