RC Shock Absorbers 101: How to Replace and Tune Your Car's Suspension

Quick Answer

To replace and tune your RC car's shock absorbers, start by removing the old shocks, then disassemble, clean, and refill them with the correct weight oil. Adjust spring preload and ride height to match your driving surface, and always check for leaks and smooth operation before reinstalling. For most bashers, a medium-weight oil and a slightly softer spring setup offer a balanced starting point.

Shock absorbers are the unsung heroes of your RC car's suspension. They control how your tires stay in contact with the ground, absorb impacts, and keep your car stable through corners. If your car bounces excessively, bottoms out, or feels twitchy, worn or poorly tuned shocks are likely the culprit. In this guide, you'll learn how to replace and tune your shocks step by step, so you can get back to driving with confidence.

Whether you're running a brushless monster truck or a drift car, understanding shock oil, springs, and preload is key to unlocking better performance. We'll cover the tools you need, the disassembly process, and how to choose the right oil weight for your conditions. By the end, you'll be able to diagnose and fix common suspension issues without guesswork.

Why Shock Tuning Matters

Shock absorbers do more than just smooth out bumps. They control the rate at which your suspension compresses and rebounds, which directly affects traction, braking, and cornering. Too much oil or a stiff spring can make the car feel skittish and lose grip on rough surfaces. Too little damping can cause the car to bottom out and bounce, reducing control.

For off-road driving, like with a 1/16 monster truck, you need shocks that can absorb big impacts without letting the chassis slap the ground. On-road racers prefer a firmer setup for precise handling. The key is to match your shock oil viscosity and spring rate to your driving style and terrain. Start with the manufacturer's recommendation, then adjust in small increments.

• Always note the current oil weight and spring preload before making changes so you can revert if needed.

Tools and Parts You'll Need

Before you start, gather the right tools. You'll need a shock wrench or small pliers, a hex driver set, a small container for oil, and a clean workspace. For replacing shocks on models like the RCG Racing MT-One, check if you need a complete shock set or just internal parts like seals and shafts.

If you're upgrading, consider aftermarket shock towers or stiffer springs to handle more power. But for most maintenance, a simple rebuild kit with new O-rings and oil is enough. Always check your manual for the correct oil weight and recommended settings.

• Use a shock stand or a block of wood with holes to hold shocks upright while filling them with oil.

How to Remove and Disassemble Shocks

Start by removing the shock from the car. Use a hex driver to unscrew the top cap or the bottom eyelet. Be careful not to lose the small springs and clips. Once removed, place the shock in a clean area and disassemble it: remove the spring, then unscrew the top cap to access the oil and piston.

Drain the old oil into a waste container. Check the piston and shaft for wear or bending. If the shaft is bent or the piston is damaged, you'll need a replacement. Clean all parts with a mild solvent and let them air dry before reassembly.

• Take photos before disassembly to remember the order of parts and any shims or spacers.

Choosing the Right Shock Oil

Shock oil viscosity is measured in weight (e.g., 30wt, 40wt, 50wt). Heavier oil provides more damping, which is useful for large jumps and high-speed stability. Lighter oil allows quicker suspension movement, which can improve grip on bumpy or low-traction surfaces.

For a basher like the MT-One, a 40wt to 50wt oil is a common starting point. For drift cars, you might go lighter to allow the chassis to roll. Always test and adjust based on how the car feels. If it's too bouncy, go heavier; if it bottoms out too easily, go heavier or add more preload.

• Write down the oil weight and spring rate you used for each track or terrain so you can replicate a good setup.

Refilling and Bleeding Shocks

Fill the shock body with oil to about 80% full. Slowly move the piston up and down to release air bubbles. Then top off the oil until it's just below the top. Screw on the top cap slowly to allow excess oil to escape. This process is called bleeding and ensures there are no air pockets in the shock.

Air in the shock causes a spongy feel and inconsistent damping. Take your time with this step. After reassembly, compress and extend the shock by hand to check for smooth operation. It should move with resistance but not stick.

• If you see bubbles after capping, repeat the bleeding process—it's better to take a few extra minutes than to ruin a run.

Adjusting Spring Preload and Ride Height

Spring preload is adjusted by turning the collar on the shock body. More preload increases ride height and makes the suspension stiffer initially. Less preload lowers the car and allows more sag. For most driving, you want a slight sag of about 10-15% of the total suspension travel.

Set the ride height so the suspension sits in the middle of its travel when the car is on the ground. This gives you equal compression and rebound for bumps and jumps. If the car sits too low, it will bottom out; too high and it will feel tippy in corners.

• Use a ruler or ride-height gauge to measure the chassis height at all four corners for consistency.

Reinstalling and Testing

Once your shocks are rebuilt and tuned, reinstall them on the car. Make sure the shock mounting screws are tight but not over-torqued. Check that the suspension moves freely without binding. Then do a bounce test: press down on each corner and release. The car should return to its original height without excessive bouncing.

Take your car for a test run on a surface similar to where you'll drive. Listen for clunks and watch for leaks. If the car handles well and doesn't bottom out, your setup is good. If not, make small adjustments to oil or preload and test again.

• After a few runs, recheck the shock oil level—it can settle and need a top-up.

Step-by-Step Shock Replacement and Tuning

1. Remove the shock: Unscrew the top and bottom mounting points with a hex driver. Keep the springs and clips in a safe place. Checkpoint: Make sure you don't lose the small retaining clips.
2. Disassemble and clean: Take off the spring and unscrew the top cap. Drain the old oil and clean all parts with solvent. Inspect the shaft for bends and the piston for wear—replace if damaged.
3. Refill with fresh oil: Choose the correct oil weight and fill to 80%. Bleed out air bubbles by cycling the piston, then cap slowly. Checkpoint: No air bubbles should remain; the shock should feel smooth.
4. Set preload and ride height: Adjust the spring collar to set ride height. Aim for 10-15% sag when the car is on the ground. Measure all corners for consistency.
5. Reinstall and test: Mount the shocks back on the car, ensuring no binding. Do a bounce test and then a short test drive. If the car bounces excessively, go up in oil weight or preload.

Upgrade and Replacement Parts for Your Shocks

• RCG Racing Tracer / MT-One Shock Towers (Front & Rear): Spare part for the RCG Racing MT-One series.These parts are also compatible with the FTX Tracer, and BlackZon Slyder range, as they share the same chassis. If you're upgrading your MT-One's suspension, these shock towers let you mount longer or differently positioned shocks, which can improve travel and adjustability without changing the whole chassis.
• RCG Racing Storm Rider Bodyshell - Red: Replacement body shell for the RCG Racing Storm Rider buggy and Monster truck.This body shell is made of heavy duty plastic and is very flexible, making it strong and long lasting. A flexible, durable shell protects your shocks and suspension from impacts and debris, reducing the chance of damage that can misalign your tuning.

Replacing and tuning your RC shock absorbers is a straightforward process that can dramatically improve your car's handling and durability. By following these steps and making small adjustments, you'll be able to dial in your suspension for any surface. Remember to keep your shocks clean and well-oiled, and don't forget to check for wear on parts like shock towers and bodyshells to protect your investment.