How to Rebuild RC Shocks: A Step-by-Step Guide to Oils, Seals, and Bleeding

If your RC car is suddenly bouncing down the street like a pogo stick, or you are "slapping the chassis" on the dirt every time you land a small jump, it is time to look at your suspension.

RC shock absorbers are packed with specialized silicone oil and tiny rubber O-ring seals. Over time, heavy impacts and microscopic dirt particles tear those seals apart, causing the oil to leak out. Driving on empty shocks will destroy your handling and eventually snap your shock shafts.

Rebuilding your shocks is a necessary rite of passage in the RC hobby. It might seem intimidating, but with the right tools and a little patience, you can get your rig handling like it just rolled off the factory line. Here is your step-by-step guide to rebuilding, refilling, and bleeding your RC shocks.

1. Gather Your Rebuild Arsenal

Before you pull the shocks off your car, make sure your workbench is prepped. Once your hands are covered in silicone oil, you won't want to go searching for tools!

• Premium Hex Drivers: A solid set of 1.5mm and 2.0mm hex drivers (bonus points if they rock a sharp royal blue, black, and white handle design!) to remove the shocks from the shock towers.

• Shock Shaft Pliers: Absolutely essential. These hold the metal shock shaft securely without scratching it. If you use standard metal pliers, you will scratch the shaft, which will instantly shred your brand-new seals!

• A Rebuild Kit: Make sure you have the exact factory replacement O-rings and plastic spacers for your specific model.

• Silicone Shock Oil: Choose your desired weight (more on this below).

• Paper Towels: Rebuilding shocks is a messy job.

2. The Step-by-Step Rebuild Process

Step 1: Teardown and Drain

Remove the shocks from the vehicle and take off the metal or plastic springs. Unscrew the top cap and dump the old, dirty oil into a waste container. Pump the shock shaft up and down a few times to force all the old fluid out of the valve.

Step 2: Disassembling the Cartridge

Using your shock shaft pliers, grip the shaft securely and unscrew the plastic rod end at the very bottom. Once the rod end is off, you can slide the entire shock shaft and piston up and out of the shock body. Next, unscrew the bottom cap of the shock body to reveal the old O-rings and spacers. Throw the old rubber O-rings in the trash.

Step 3: Cleaning and Installing New Seals

Spray the empty aluminum or plastic shock body out with motor cleaner or isopropyl alcohol to remove the gritty residue.

• The Pro Trick: Before installing the new rubber O-rings, soak them in a drop of fresh shock oil (or a dedicated O-ring grease). Dry O-rings will tear during installation. Drop the new lubricated O-rings and plastic spacers back into the bottom of the shock and tighten the bottom cap.

Step 4: Reinstall the Shaft

Carefully slide the shock shaft back down through the body and through your brand-new seals. Re-attach the bottom rod end using your shock shaft pliers.

3. The Most Critical Step: Refilling and "Bleeding"

Filling the shock is easy; removing the trapped air (bleeding) is where the magic happens. If you leave air bubbles in the oil, your shocks will feel "spongy" and inconsistent.

1. The Fill: Hold the shock perfectly upright. Fill the shock body with fresh silicone oil until it is about 2 millimeters from the top threads.

2. The Pump: Slowly—very slowly—pull the shock shaft all the way down, and push it all the way up. Do this 4 or 5 times. You will see dozens of tiny air bubbles rise to the surface.

3. The Wait: Place the shock upright in a shock stand (or a drilled block of wood) and leave it alone for 5 to 10 minutes until every single air bubble has popped at the surface.

4. The Cap-Off: Once the oil is crystal clear, top it off so the oil is perfectly level with the top of the shock body. Slowly screw the top cap back on.

Test it: Push the shock shaft all the way in. It should feel smooth and consistent. If the shaft forcefully pushes your finger back out, you have too much oil (hydro-locked). Unscrew the cap slightly, let a tiny drop of oil bleed out, and retighten.

4. Understanding Shock Oil Weights

Shock oil is measured in "Weight" (wt) or "Centistokes" (cSt). The higher the number, the thicker the oil, and the slower your suspension will react.

• Light Oil (20wt - 30wt): Very thin. The shock compresses and rebounds instantly. Best for: 1/10 scale buggies, technical indoor clay tracks, and highly bumpy, rutted terrain where the tires need to react quickly to stay glued to the dirt.

• Medium Oil (40wt - 50wt): The standard "Goldilocks" zone. Best for: Short course trucks, truggies, and general all-purpose backyard bashing.

• Heavy Oil (60wt - 80wt+): Extremely thick like honey. Best for: Massive 1/8 scale monster trucks and skate-park bashers. Thick oil prevents the heavy chassis from violently slapping the concrete after landing a 15-foot jump.

Hit the Dirt with Confidence

A fresh shock rebuild completely transforms how your RC car handles. Instead of bouncing out of control and flipping in the corners, your rig will stay planted, absorb the heavy hits, and launch off ramps with perfect symmetry.

Time to Reseal and Refill? If you are staring down a puddle of leaking shock oil on your workbench, we have your back. Shop the digital warehouse at Naughty Boy RC for a massive selection of premium silicone shock oils, factory O-ring rebuild kits, and precision shock-shaft pliers. As an online-only, direct-to-door retailer, we ship the exact maintenance gear you need right to your house so you can get back on the track!