Thanks again everyone, this is like a crash course in bicycle mechanics. I have a question that may be a silly one. I understand that in the front, the big chain ring is for more speed/power and progressively smaller ones are more for climbing. I also understand that in the cassette in the back, the opposite is true—the bigger the cog (ie, greater number of teeth), the lower the gear.

So my question is this: how do I compare two different cofigurations? For example, how different would it feel to climb in 34 front /25 rear versus, say, 36 front/ 27 rear? (If those are even possible configurations.) You can’t just add the numbers for a comparison. So is it just be experience that you know? Would I even notice the difference? As I demo compacts vs triples, it’s hard to gauge these subtleties. I can only be on one bike at a time, after all, and even if I play with bikes back to back climbing hills, I’m obviously more fatigued the second time around. On the Trek I am considering, the lowest gear combination is 34/25 on the compact, 30/27 on the triple. Is that a huge difference--one gear? Two gears? They only have the compact for me to demo.

Maybe I’m overthinking this, but I do keep getting mixed reactions on the compact vs. triple debate. I visited a second LBS and they, too, thought the compact was the way to go, saying that it shifted much smoother. (And they had both compacts and triples on the floor, so no apparent bias.) I also want to make sure I consider some of the points some of you have made, such as making sure I don’t sacrifice gears in “my” typical spinning range.

And frankly, at this point, I’m just curious about how this gear business really works. I had never even contemplated the term “gear inches” until aicabsolut mentioned it. The big ring/little ring thing seems so counterintuitive to me!