Join Date: Feb 2004
Location: St Peters, Missouri
Bikes: Rans Rockst (Retro rocket) Rans Enduro Sport (Retro racket) Catrike 559, Merin Bear Valley (beater bike).
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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.