The pinion and spur gears are the gear combination that transfers the power from the motor to the wheels of your RC car. Correctly setting up these gears will take your RC car’s performance to another level.
But what makes a good pinion and spur gear setup?
his article will briefly describe what the spur and pinion gears do. Then we’ll look at how to change the stock gearing to optimize it based on how you drive your RC car.
Keep reading to find out more.
RC Car Pinion & Spur Gears: An Overview
The pinion and spur gears work together in an RC car to transfer power from the motor to the wheels.
In this image of my Traxxas Rustler 2WD, the pinion gear is the small gear on the left attached directly to the motor shaft. The spur gear is the large gear attached to the transmission or differential.
When the motor spins the pinion gear, it meshes with the spur gear and transfers the rotational force to the wheels, causing the RC car to move.
Pinion gears connect directly to the motor’s output shaft and transfer power to the spur gear, so they take a lot of wear.
Official Traxxas Rustler pinion gears vary as follows:
- Rustler 2WD: between 19 and 28 teeth
- Rustler VXL: between 25 and 31 teeth
- Rustler VXL 4WD: between 11 and 20 teeth
Although the pinion gear’s size affects the car’s speed and torque, it must be combined with an appropriately sized spur gear to balance power and acceleration.
The Spur Gear On Your RC Car
The large spur gear meshes with the pinion gear and transfers the power to the RC car’s wheels. Spur gears are often made from hard-wearing plastic, but metal gears are also available.
Unlike pinion gears, spur gears are configured differently depending on whether your car is a 2-wheel-drive or 4-wheel-drive.
If you have a 2WD car, the spur gear is mounted directly on the drive shaft between the two wheels.
In a 4WDrc car, the spur gear is mounted on a central driveshaft that runs between the drive mechanism for the front and rear wheels. The 4WD gearing system can get more complex since you can introduce additional gearing front and rear.
Official Traxxas Rustler spur gears vary as follows:
- Rustler 2WD: between 76 and 86 teeth
- Rustler VXL: between 76 and 83 teeth
- Rustler VXL 4WD: 54 teeth
Pinion and spur gears are typically made from metal or plastic materials. Aftermarket or high-end RC cars may include carbon fiber or aluminum gears.
Metal gears are stronger and more durable. They’re commonly made from steel, brass, or aluminum. Steel is the most common material due to its strength.
Plastic gears, on the other hand, are lighter and less expensive than metal gears. However, they’re not as durable or able to handle as much torque. They are commonly made from nylon, acetal, or polyoxymethylene (POM). They are often used in entry-level or beginner RC cars.
As mentioned earlier, the gear ratio is the number of teeth on the pinion gear relative to the spur gear. A higher gear ratio results in a higher top speed but less low-end torque. In contrast, a lower gear ratio will provide more torque but less top speed.
Taking a few minutes to understand the role of pinion and spur gears in driving your car can help you tweak your car for the best performance for the driving conditions.
How to Match Gear Ratios On Your RC Car
The combination of different pinion and spur gears on your RC car will change the car’s performance.
Setting up your RC car for speed runs and fast acceleration requires a different gear ratio than crawling over rough terrain.
A small pinion gear combined with a larger spur gear will give you a car with fast acceleration off the line. However, the speed will max out very quickly.
A pinion gear slightly larger than the spur gear will give slower acceleration but a faster top speed as the motor gains momentum.
Larger spur gears typically translate into faster acceleration but lower top speeds and power.
However, the size of the gears is not the only parameter to consider.
Both spur and pinion gears will have a tooth count and a tooth pitch, or the number of teeth per inch. These characteristics play a role in balancing power and acceleration.
The higher the tooth pitch on the spur gear, the more torque will be delivered. The higher the tooth pitch on the pinion gear, the more speed will increase the car’s performance.
The combination of the number of teeth on the gears will determine the gear ratio. The RC car gear ratio can be calculated by dividing the spur gear tooth count by the tooth count of the pinion gear.
Here’s an example.
Imagine a spur gear with 100 teeth and a pinion gear with 20 teeth. That makes the calculation look like this.
Spur gear teeth / Pinion gear teeth = Gear Ratio
100 ÷ 20 = 5
The gear ratio in this example is 5:1. This means the pinion gear will rotate 5 times to a single rotation of the spur gear.
A high gear ratio is the equivalent of low gear and will give quick acceleration off the line but a slower top speed. It will also offer higher torque or more power to the wheels, which is excellent for navigating soft sand or obstacles.
A lower gear ratio on your RC car will result in a slower pull-off but a higher top speed. Unfortunately, it also causes more strain on the motor and higher temperatures, resulting in shorter run times. This kind of setup is not suitable for crawlers.
Tweaking the gear ratio helps you get the perfect balance between power, acceleration, and speed. This enables you to tune your RC car to your driving style and the terrain you drive on.
Wrapping It Up
Gearing on an RC car is not complicated, especially once you try a few combinations on your car and see the difference in performance.
Changing the gearing can improve or degrade your car’s performance. The best tactic is to make minor adjustments in the gearing ratio and test the performance difference until you find a combination that works for you.
A word of warning, however. Don’t go to extremes in gearing ratios on your RC car. You may risk burning out your motor, ESC, or both.