Will I have a low enough gear for this 9% climb? A big enough one so I don’t spin out on the descent? How many genuinely different gears do I actually have on my bike? You usually answer these by feel, or by swapping a cassette to find out. 2PEAK’s new Gear Calculator gives you the answer in black and white: for every chainring-and-sprocket combination, it shows the gear ratio, the rollout and your speed at a given cadence — and it flags the gears that duplicate each other and the combinations to avoid. Let’s look at what it does and how to use it.
