How to Make Suspension for an RC Car: Designs, Parts, Tuning
The simplest RC car suspension is a pivoting arm held up by a spring: that alone soaks up bumps on a DIY or 3D-printed car. Hobby-grade cars add an oil-filled damper inside the spring (a coil-over shock), which stops the car bouncing. To make or improve suspension you choose a layout (swing arm, double wishbone, solid axle with links), fit springs that hold the car at the right ride height, and tune the shock oil. Here are designs you can build and the settings that matter.
By Kyle HilsonUpdated: October 20264 min read
Which suspension layouts are used on RC cars?
| Layout | How it works | Found on | DIY difficulty |
|---|---|---|---|
| Spring-only swing arm | Arm pivots at the chassis, spring pushes it down | Toys, simple DIY cars | Easy |
| Double wishbone (A-arms) | Upper and lower arm per wheel, coil-over shock | Buggies, short course, touring cars | Medium |
| Solid axle with 4-link | Axle located by four links, coil-overs | Crawlers (Axial SCX10, Traxxas TRX-4) | Medium |
| Leaf springs | Axle on flexible spring packs | Scale trucks and trailers | Medium |
| Trailing arm | One arm per side pivoting at the front | Rear of some on-road cars | Easy–medium |
How to make a simple suspension for a DIY car
- Pivot: mount each wheel’s arm on a pin or screw through the chassis, with a bushing or bearing so it moves freely without play.
- Spring: a compression spring (from a ballpoint pen for very light models, or RC shock springs) between the arm and a chassis mount. Place it as far out on the arm as possible for a softer, more controlled feel.
- Stop: limit travel with a screw or strap so the arm can’t overextend.
- Damping (optional): buy cheap RC coil-over shocks; they include springs and screw on with ball studs.
- Test: push the car down and release: it should come back once and settle, not bounce several times.
3D-printed cars often use printed arms with metal pins and off-the-shelf RC shocks, which is far more reliable than printed springs. Frame design is covered in how to build an RC car frame. A servo is not used in suspension; servos are for steering and gear shifting.
How do RC shocks work?
A shock is a cylinder filled with silicone oil and a piston with holes. When the suspension moves, oil flows through the holes and slows the movement. The spring carries the car’s weight; the oil controls how fast it moves.
| Setting | Change | Effect |
|---|---|---|
| Shock oil | Thicker (higher cSt) | Slower, firmer damping; less bouncing, slower response |
| Piston holes | Fewer or smaller | Firmer damping, especially on big hits |
| Spring rate | Stiffer | Less body roll, rides higher, less grip on rough ground |
| Preload collar | More preload | Raises ride height (doesn’t make the spring stiffer) |
| Shock angle | More upright | Firmer feel |
Typical starting oils: about 300–500 cSt for 1/10 buggies and short course trucks, thinner for crawlers that need soft, slow articulation. Your car’s manual gives the stock values.
Tuning ride height and fixing problems
| Problem | Try |
|---|---|
| Car bounces after jumps | Thicker oil or fewer piston holes |
| Bottoms out on landings | Stiffer springs or more preload; check ride height |
| Rolls over in corners | Stiffer springs, lower ride height, sway bars |
| Skips over bumps, loses traction | Softer springs or thinner oil |
| Shock leaks | Replace O-rings, refill and bleed air out |
| Uneven ride height left/right | Equalise preload; check for bent arms or shafts |
How to refill an RC shock
- Remove the shock, unscrew the cap and empty the old oil.
- Push the shaft fully down (or to about 2/3 for emulsion shocks, per manual).
- Fill with oil to just below the top, move the piston slowly to release air bubbles, and let it rest.
- Top up, fit the cap slowly so excess oil escapes, and check the shaft moves smoothly without air pockets.
- Rebuild both shocks of an axle the same way so they match.
FAQ
How do I make easy suspension for an RC car?
Pivoting arms with a spring on each, plus a travel stop. For better control, add cheap coil-over RC shocks.
What shock oil should I use?
Start with the manual’s value. Roughly 300–500 cSt suits many 1/10 bashers; crawlers often use softer setups.
Do preload spacers make the spring stiffer?
No, preload only changes ride height. Change the spring for a different rate.
Can I use a servo for suspension?
Not in normal cars. Servos do steering and shifting; suspension needs springs and dampers.
More on this topic: the complete RC Cars guide covers the basics behind this article.
About 20 years in RC. Mostly boats in the NAVIGA Mini Eco Expert class, with many self-made parts; also a King Motor Baja 5B, a home-built electric plane, home-built nitro planes he has flown, and an RC helicopter. More about SwellRC
