Why your RC car pulls to one side
A drift to the left or right is almost always trim, binding, or a tweaked chassis — here is how to find which.
A steady pull to one side has a short list of usual causes. Work through them in order:
1. Steering trim. Hold the car off the ground, leave the sticks centered, and adjust the trim until the front wheels point dead straight. This fixes most pulls in seconds.
2. Binding or drag. Spin each front wheel by hand — they should coast freely and equally. A dragging brake, a tight or dirty bearing, or debris in the driveline on one side will pull the car that way.
3. Servo saver / linkage. A servo saver that is too loose will slip under load and let the wheels wander. Check it isn't slipping and that the steering links aren't bent.
4. Tweak. If the chassis sits with unequal corner weight (a 'tweak'), it will launch to one side. Set equal ride height left-to-right and check the shocks are matched.
5. Alignment. Uneven toe or a bent hub/arm from a crash will steer the car on its own. Compare left and right and replace anything bent.
Source: Standard RC setup/troubleshooting technique