How To: Set a Gear Mesh on an RC Vehicle

'Gear Mesh' is referring to how well any two gears mesh together.

A poorly set gear mesh is the most common cause of stripped or melted spur gears. The gear mesh should be checked and adjusted regularly and also when the spur gear, pinion gear and the motor is replaced.

In this article, I’ll cover how to check and adjust your gear mesh on your radio controlled car.

Don't like reading? Watch the video below or watch how to set your gear mesh here.

So close, and yet so far. This describes the correct gear mesh setup. It also describes the success I had during early attempts to do it myself. On many modern high-performance radio control cars, the mesh between the pinion gear (the little one on the motor) and the spur gear (the big one the little one goes onto) is adjustable. This enables fine tuning of acceleration and top speed through changing gear ratios. This also enables the gears to completely shred themselves almost immediately if the distance between the two gears, and therefore the contact patch of the teeth, is not right.

Too loose and you’ll be stripping teeth faster than you can say “what’s that funny grinding noise?” and too tight and you’ll be burning out electronic components faster than you can say “what smells like burning?”

Whether you’ve changed to a new pinion, you’re a maintenance hero, or your car sounds funny after that last massive jump that you almost landed, it’s time to check your gear mesh.

Access your gears

The first step is to gain access to the pinion and spur gear – this varies from vehicle to vehicle. On most rear wheel drive cars, the motor is mounted at the back of the car and the gears can be accessed by taking off 2 screws that hold on the gear cover. 4wd cars have the same principle, the distance between the gears, but accessing the motor mount to actually adjust this can be much more difficult.

Check your gear mesh

Once you’ve made it into the motor mount to adjust the gear mesh, the rest is easy. Before we go loosening any adjustment/mounting screws, it is a good idea to check the gear mesh as it sits. To do this, hold the pinion still, and gently rock the spur gear back and forth.

We are after a small amount of backlash between the spur and pinion. Too much movement and the gears will strip. Too little and the gears can still strip, too. A too-tight gear mesh also can overheat the motor and ESC, reduce performance, and ruin battery runtime.

Adjust your gear mesh

If the mesh isn’t where it should be, loosen off the motor screws a little, and move the motor closer or further until the mesh looks good.  A good way of getting the right distance is putting a small strip of paper between the pinion and spur. Tighten down the motor screws, remove the paper, and you’ll be left with a near-perfect mesh. Move the spur gear around by hand a full revolution to make sure the mesh stays even as the gears turn.

Check your gear mesh again

Lastly, this is a good time to check that the pinion and spur are making full contact across their teeth. The pinion can move up and down the motor shaft, and sometimes only half of the gear’s teeth will actually be making contact with the spur – I’ve been guilty of this on many cars, not that I’d ever admit it. To adjust, loosen the grub screw on the pinion, and position it so it matches the spur, making full contact across the whole tooth. If the pinion is thinner or wider than the spur, put it as close to the middle as you can. A small amount of blue thread locker on the grub screw will hopefully help this stay in place, too.

If you’ve done this right, your car (and wallet) will thank you, and you can sleep well knowing your gear mesh is perfect.