If you’ve ever looked at a factory specification sheet for an
Electric tricycle differential gearbox, you’ve probably noticed two numbers popping up everywhere: 16T and 18T.
To a procurement manager, these might just look like random numbers. But to an engineer like me, those two teeth represent a fundamental difference in how your vehicle will perform. One of the most common emails I receive is: "Which one should I buy?" Today, I’m breaking down the "Teeth Count" mystery so you can make the right call for your fleet.
Don't Let the Numbers Confuse You
When we talk about 16 or 18 teeth, we are usually referring to the input shaft gear or the internal sun gears. This count dictates the "Gear Ratio" and the "Module" (the size and strength of each gear tooth).
In my experience, choosing the wrong teeth count doesn't just affect speed—it can lead to a "mismatch" that causes excessive vibration, noise, and eventually, a total transmission failure.
The Impact of Teeth Count on Motor Output
The relationship is simple: the number of teeth affects the mechanical advantage.
The 16-Tooth (16T) Gearbox: In most standard setups, fewer teeth on the input side often mean a higher reduction ratio. This is my "Go-To" for torque-heavy applications. If your motor is a standard 800W or 1000W and you need to move heavy loads, 16T provides that extra "punch" to get the wheels turning from a dead stop.
The 18-Tooth (18T) Gearbox: More teeth generally result in a "taller" gear. This is designed for speed and efficiency. If you are building a lightweight passenger trike or a mobility scooter that needs to reach 35-40 km/h comfortably, the 18T setup is much smoother and more energy-efficient.
Technical Comparison: 16T vs. 18T Differential Gear
Based on the stress tests I've conducted in our lab, here is how they typically stack up:
Spline Count and Axle Compatibility
Here is a mistake I’ve seen even experienced buyers make: focusing on the teeth count but forgetting the splines.
The spline is the grooved part of the shaft that connects to your motor or axle. I always double-check the diameter (usually 20mm or 25mm) alongside the teeth count. If the differential gear specifications don't match your motor's output shaft, you'll end up with "slippage," which will strip the gears in a matter of days.
My Advice: Test Before You Bulk Buy
Before you place an order for 500 units, I always recommend requesting a sample of both.
My Insider Tip: Install a 16T and an 18T on the exact same trike model. Measure the battery consumption over a 10km loop. You’ll often find that for your specific vehicle weight, one "teeth count" will be significantly more energy-efficient, saving your end-users money on electricity.
