Gear Mesh

Gear mesh is how deeply an RC car's pinion engages the spur gear, set by sliding the motor in its mount. Team Associated's check: the spur should rock back and forth without moving the pinion.

Also called:

Mesh, backlash, gear lash

In practice

You set mesh by loosening the motor screws and sliding the motor toward or away from the spur, then locking it down. The RC10B6.4 manual gives the check in one line: “You should be able to rock the spur gear back and forth in the teeth of the pinion gear without making the pinion gear move.” Associated is blunt about the stakes: “a gear mesh that is too tight or too loose will reduce power and damage the gear teeth.” Reset it after every pinion or spur change and after any crash hard enough to move the motor. Pinion and spur must share a pitch, and So Dialed notes finer pitches have smaller, more fragile teeth than coarse ones — less margin when the mesh is wrong.

Why it matters

Mesh never shows up on a setup sheet, but a bad one strips a spur in the middle of the main and turns a cheap gear change into a DNF.

Go deeper

Read the full post:

RC Gear Mesh and Backlash: Setting Spur and Pinion Right

Sources

RC10B6.4 Team Kit Manual — Team Associated (PDF) — manufacturer’s rock-the-spur mesh check, the loosen-and-move-the-motor fix, and the warning that too tight or too loose reduces power and damages teeth
Gear Pitch — So Dialed — meshing gears must share a pitch, and finer pitches have smaller, more fragile teeth than coarse ones