For a 24-speed mountain bike with a 3-ring front and 8-ring rear, which gears should you use while riding? With so many gear combinations, how do you choose and switch between them?

1. For everyday riding, use the 2nd chainring up front and select the 5th, 6th, or 7th cog in the back (avoid using the largest cog).
2. On flat roads, if you want to increase speed, shift the rear cog to the 8th position to create a 2-8 gear combination, achieving speeds of around 30–35 km/h. If you want to go even faster, shift to the 3rd chainring to create a high-speed 3-8 gear combo. At a constant pedaling cadence, this can reach speeds of 35–40 km/h. To slow down, first reduce the chainring to the 2-8 combo, then shift down the rear cog to 2-7, 2-6, or 2-5.
3. When going uphill, keep the chainring gear the same and shift down the rear cog. Depending on the slope’s steepness, you can shift to the 4th, 3rd, 2nd, or even 1st rear cog.
4. The 1st chainring is generally not used unless you’re climbing uphill.
Among all the gear combinations on a mountain bike, it is recommended to use the 2-5, 2-6, or 2-7 combos for the following reasons:

First, it reduces resistance when starting off.
Second, it protects your knees: consistently using high-output combinations like 2-8 or 3-8 keeps your knees under constant tension and strain, which can cause significant damage over time.
Third, it reduces wear on the rear cogs and extends their lifespan: frequently using high gear ratios accelerates wear on the most stressed parts—the largest chainring and smallest rear cog—impacting the overall longevity of the drivetrain.