Quote Originally Posted by Melalvai View Post
Keep riding, it'll be second nature to you in no time.

I've been riding for a couple years and I had no idea that road bike shifters don't have numbers. I'm not ashamed to admit it.

Crosschaining is when the chain is on the biggest gear in front, and the biggest gear in back. If you look, you'll see that it is as far to the right as it can be on front, and as far to the left as it can be in back. Or, smallest and smallest, then it's as far left and far right front/back.

If you only have two chainrings up front, I think it doesn't matter? But if you have 3 chainrings, it's bad to have it in those extremes, because it can cause chain stretch, which will wear out the teeth on the thingies, I mean the sprockets, and then you won't be shifting smoothly. You don't need to use those extremes, because they overlap with gear ratios you can achieve using the middle chainring.
It still matters with a double, but it will be harder to crosschain than with a triple. You just don't want to be spending much time, if any, in your little ring little cog or big ring big cog. There will still be too much chain rubbing on the FD. There's a much smaller range of rear cogs that don't cause you to crosschain when you have a triple up front because of the limitation with the rings and FD position per ring.