Bicycle Mechanics - New cassette - new chain?

Hey. I just got a new cassette to help with climbing and have heard that I should put on a new chain as well. My current chain (Dura-Ace) has 400 miles on it and I don't want to have to buy a new one unless I should. . .what is the prevailing wisdom on this?

Thanks
Adam

Hey. I just got a new cassette to help with climbing and have heard that I should put on a new chain as well. My current chain (Dura-Ace) has 400 miles on it and I don't want to have to buy a new one unless I should. . .what is the prevailing wisdom on this?

Thanks
Adam
My advice. Measure old chain for elongation (cheap tool from Park or search the forum/see Sheldon Brown's site for formula) and if it is within specs no need for new chain. I would think that with only 400miles on it you should be good to go (assuming you did not change the cogs so much that it would now be too short).

+1

have it checked, but 400 miles shouldn't have hurt the chain.

+3, but I think your main concern should be chain length(# of links). Not knowing where you started from and exactly what you changed to cant say for sure w/out more info.

Currently 11-23 going to 12-27.

Going up from a 23t to a 27t you'll need a couple more links in your chain plus a longer cage derailleur to take up the slack.

Going up from a 23t to a 27t you'll need a couple more links in your chain plus a longer cage derailleur to take up the slack.
But other than this, there's no reason to replace a barely-used chain, unless you kept the bike outside all the time and it started to rust. And with a D/A chain, I doubt that you did so.

I'm not so sure.

Depending on how your chain was sized before you might not need to add links. The issue is if the chain is long enough to safely cover the big/big combination. If it was my bike I'd shift up (gingerly) with the bike on the workstand. If you still have a little slack in your derailleur arm, your chain length is good.

The same goes for your rear derailleur. In most cases, a short arm rear derailleur will handle a 12/27 with a double crankset. If you have a triple, your bike would have already needed a long cage rear derailleur for the 11/23.

+1 Rg