Adjusting and maintaining shock absorbers: how to make your RC car drive better

Shock absorbers are one of the most important parts of your RC car when it comes to handling. They determine how your car lands after a jump, how much it leans in a corner, and how well the tires stay in contact with the ground. The good news: with a few simple adjustments, you can significantly improve handling.

In an earlier article, we discussed how to choose the right shock oil. Here, we'll cover the rest of the setup and maintenance.

Spring and shock: two different jobs

A shock absorber consists of two parts, each with a different job:

• The spring supports the car's weight and determines how stiff the suspension is.
• The shock (oil and piston) determines how quickly the suspension compresses and rebounds.

A common mistake is trying to compensate for a spring that's too soft with thicker oil. That doesn't work: the car will still bottom out; it will just do so more slowly.

1. Set ride height with preload

Use the clips or adjuster ring above the spring to change the preload. More preload raises the car, but does not make the spring stiffer. So use preload only to set the ride height.

A handy rule of thumb for bashers and buggies: drop the car from a height of about 20 cm onto a flat surface. After landing, it should return to the correct height without bouncing. Measure the ride height at the front and rear, and make sure it's the same on the left and right.

2. Springs: softer or stiffer

• Softer springs provide more grip on bumpy terrain and let the car lean more in corners.
• Stiffer springs keep the car flatter in corners and on landings, but provide less grip on rough terrain.

Want your car to turn in more? Make the rear a little stiffer or the front a little softer. Want more stability? Do the opposite.

3. Mounting points

Most cars have several holes in the shock tower and suspension arm. Moving the shock changes its angle and leverage:

• More angled (with the top further inward) makes the suspension softer and more progressive. More grip, more body roll.
• More upright makes the suspension stiffer and more direct.
• Further out on the suspension arm makes the suspension stiffer; further in makes it softer and increases suspension travel.

4. Oil and pistons

Thicker oil or a piston with smaller or fewer holes provides more damping: the car moves more slowly and lands more smoothly. Thinner oil or larger holes gives a faster response. Always change one thing at a time so you know what effect it had.

5. Crawlers are different

With crawlers, you want as much suspension travel and grip as possible. Soft springs and long shocks let the axles articulate more, keeping all four wheels in contact with the ground. Don't use too much preload, or the car will lift itself up and become unstable on slopes.

Maintaining shock absorbers

Shock oil wears out, gets contaminated, and leaks over time. You'll notice leaking or "empty" shocks when the car keeps bouncing after a jump. We recommend checking your shocks every 10 to 20 driving sessions, and more often if you drive a lot in dust or mud.

How to change the oil

1. Remove the shock and take off the spring.
2. Unscrew the cap and pour out the old oil. Clean everything with a cloth.
3. Check the O-rings and the piston rod. A scratched rod or worn O-ring can cause leaks.
4. Push the piston all the way down and fill the shock almost to the top with fresh oil.
5. Slowly move the piston up and down a few times, then let the shock rest for a few minutes so the air bubbles rise to the top.
6. Add more oil if needed, fit the cap or membrane, and tighten it. Excess oil will escape through the hole in the cap.
7. Check that all the shocks rebound at the same speed. Always do this in pairs (front left and right).

Use good tools for the job, such as shock pliers, so you don't damage the piston rod.

Conclusion

Start with the correct ride height, then choose springs that match your car's weight and set the oil to suit your terrain. Change one thing at a time and keep track of what you do. Regular maintenance will also help your shocks keep working reliably for a long time. Looking for new shocks or parts? Browse our collection of shock absorbers.