Of course, your fitness level is an important factor when it comes to chainring choice. If you don’t ride that often, but still ride in mountains / hilly terrain, I would recommend riding a smaller chainring. This keeps you pushing the same cadence as you switch gears to head up the mountain. For a long time, I thought I could ride a 34 tooth chainring on every type of trail. When I decided to test out a smaller ring, I found that I was saving tons of energy riding uphill sections because my cadence remained the same. If your have the feeling that you don’t have enough gears halfway up the mountain, you should also switch to a smaller chainring. However, when you are riding downhill and you cadence increases to out of control, you might want to consider looking into a larger chainring.