Spur and Pinion Gear Explained (Simplified)

Want to tune your gears other than just gear ratio? the Advantages of Smaller Pinion vs Bigger Pinion – Smaller Spur vs Bigger Spur for Spur and Pinion Gear Explained (Simplified)

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Tuning with Pinion

The Pinion should be the main gear you change. It has a bigger impact on the gear ratio and overall has more options for your gear ratio.

Bigger Pinion Advantages

Gives more speed – if too big you will lose out on both top speed and acceleration
Better gear mesh – more teeth engagement – mainly making the two gears last longer.

Smaller Pinion Advantages

Always give more torque
Gives more acceleration – if too small you will lose out on both top speed and acceleration
On most 2wd cars it will move – (Rear Motor cars weight is more forward) – (Mid Motor cars weight is more rearward)
On most 4wd cars (shaft-driven) it will move the motor weight to the middle
Generally, a slightly better handling and balance car – the keyword is “slightly” It’s better to have the right gear ratio.
Takes less power from the motor – just less rotating mass on the motor shaft.
The motor has less stress and runs cooler

Smaller Pinion has more advantages

But the advantages are small!!! You should only go to Smaller Pinion if you can achieve the Top Speed you need or if your motor is running hot.

Tuning with Spur

The Spur is more for fine-tuning the gear ratio. For many RC models, you will find you only need or use one size.

Bigger Spur Advantages

Like the smaller Pinion
- Always give more torque
- Gives more acceleration – if too small you will lose out on both top speed and acceleration
Like the bigger Pinion (Below)
- Better gear mesh – more teeth engagement with the spur has many advantages – mainly making the two gears last longer.

Smaller Spur Advantages

Like the bigger Pinion
- Gives more speed – if too small you will lose out on both top speed and acceleration
Like the smaller Pinion (Below)
- On most 2wd cars it will move – (Rear Motor cars weigh more forward) – (Mid Motor cars weigh more rearward)
- On most 4wd cars (shaft-driven) it will move the motor weight to the middle
- Usually, a slightly better handling and balance car – the keyword is “slightly” It’s better to have the right gear ratio.

Why Bigger Spur is usually better.

I generally run the biggest recommended or commonly used Spur for the model that I’m running. The reason is more to do with the ability to run a smaller Pinion – I’m able to keep less rotating mass off the motor, giving the car a slight power advantage. You also have better gear mesh.

When should I run a Bigger Pinion? paired with Smaller Spur…

(In short) If you’re on tracks where you are wide open and need to carry speed with momentum. It’s sometimes better to have more rotating mass (Bigger Pinion) to carry the car – for instance, keeping speed up over a hill or a long turn trying to slow down your momentum. Think like a train being pushed by its weight to keep its momentum – whereas if it did not have the weight it would scrub speed off on such hill or turn.