How to Change the Gear Ratio: Alpha 2Updated 2 hours ago
The Alpha 2 comes standard with a Gates SideTrack belt drive system. From the factory, it features a 50-tooth front sprocket and a 22-tooth rear cog, resulting in a 2.27 gear ratio. This setup ensures a smooth and easy ride with quick acceleration, making it great for most riders.
However, if you’re a stronger rider or mostly ride on flat ground, you might prefer a gear ratio that gives you more resistance and a faster cruising speed. Gates now offers a 20-tooth rear cog, which increases the gear ratio to approximately 2.5. This means you’ll spin the pedals more slowly at higher speeds and avoid “ghost-pedaling” (when your legs are spinning but not doing much because the motor is outpacing your cadence), especially in Pedal Assist level 1.
Even better, this upgrade still works with the original 118-tooth belt, so no need to buy a new one.
Here’s how to install the 20-tooth rear cog on your Alpha 2.
Tools Required
- 19mm wrench
- Gates belt whip (or equivalent)
- A basic strap wrench will likely work if you don't want to go in on a Gates tool.
- The Park BDT-1 is unlikely to work since we're working with ST, not CDC, CDN, or CDX.
- Park Tool BBT-9 or equivalent
- 4mm T-handle hex
- 5mm hex wrench
Installation
- Remove the rear wheel.
- Use the Gates belt whip and BBT-9 to remove the rear cog from the freehub body.
Ah, belt life. - Install the new cog onto the freehub body, then torque it down
22T cog show, it's the same process with the 20T
This cog is reversed, but you'll install yours with the letter facing outboard 
Torque it down! - Install the rear wheel
- Adjust the belt tension
Woohoo! You've just installed a new rear cog on your Alpha 2! Get ready for many miles of smiles with your new gear ratio. New gear. New YOU!