Originally Posted by ericm979

You may or may not be able to do it. It depends on your frame's derailleur hanger geometry. The only way to find out is to try it.

Make sure that your chain is long enough to go over the large chainring and large cog. If it isn't and you accidentally shift into that combo your ride will be over. It's better to have the chain a little loose in the small-small combo. That just makes noise but doesn't break things.