RC car skittish over bumps? Soften and free up the suspension
If the car deflects off bumps instead of soaking them up, the suspension is too stiff or something is binding. Go thinner on shock oil, softer on springs, add droop, and check the chassis isn't tweaked.
Why it happens
Suspension has to let the wheel move up and down quickly to stay in contact with the surface. Thick oil, stiff springs, too little droop or a binding part all stop the wheel following the ground, so the car hops instead.
Check in this order
- Shock oil. Go thinner, one step at a time; 100 cSt is a noticeable change.
- Springs. Softer springs before changing anything geometric.
- Droop. Add droop so wheels can extend down into dips.
- Binding. With springs off, each arm should fall freely under its own weight. Anything that catches is binding.
- Tweak. A bent or twisted chassis leaves one corner unable to absorb anything. Check corner weights on a flat board.
Parts that fix it
- Shock oil: Shock oil
- Springs: Spring
- Dampers and shock parts: Damper
- Shock towers: Shock tower
FAQ
Should I use thinner or thicker shock oil for bumpy surfaces? Thinner. It lets the suspension move faster to follow the surface.
What is droop on an RC car? How far the wheel can drop below its resting height. More droop helps the tyre stay in contact over dips.
How do I check if my RC chassis is tweaked? Set the car on a flat surface and lift each corner slightly; both sides should lift at the same point. If one side lifts first, the chassis or suspension is tweaked.