You won't need to shorten the chain. As noted above, my crank is 46-36-24 and cassette is 11-34. The chains I use are 116 links and I put them on without shortening them on my Surly LHT. In most cases a long chain is not an issue unless you run in the 24 crank and 11 cassette combination then you will get sage and perhaps the rear derailleur touching the cassette if not properly adjusted. The real issue is when one runs a chain that is too short -- that could lead to a broken rear derailleur.