Bearings are the least glamorous parts on your truck. Nobody posts a bearing on social media. But a bearing costs a few bucks, and a seized one can melt a hub carrier, chew up an axle and turn a fast truck into one that drags to the left like it is mad at you. On our repair bench, "my truck pulls to one side and I already checked the steering" very often ends with a crunchy little bearing in a wheel hub.
This guide covers how to tell when a bearing is going bad, how to clean and re-oil the ones worth saving, and how to size and replace the ones that are done. It works for most electric 1/10 and 1/8 cars and trucks. The method comes from RC Car Action, the FMS Hobby bearing guide and plenty of dirty fingers at the bench.
The Short Answer
Pull the wheel and spin the bearing by hand: smooth and quiet is good, gritty or notchy means clean it, and if it is still rough after cleaning (or has a torn seal, pitting or rust), replace it with the same size, which is printed as inner diameter x outer diameter x width in millimeters.
- Check: after wet or dusty runs, and any time the car pulls to one side for no obvious reason.
- Clean: pop the rubber seal with a hobby blade, flush with motor spray, dry, then add one or two drops of light bearing oil.
- Never use soap and water. Leftover moisture turns into rust.
- Replace: match the size exactly, and choose rubber-sealed (2RS) bearings for bashing in dirt and water.
1. How to Tell If an RC Bearing Is Bad
You cannot judge a bearing with the wheel on. Tires, diffs and the slipper all add drag, and they hide what is going on. Pull the wheel, then turn the axle or hub by hand. FMS Hobby puts it simply: rotation should be "fluid and silent." Everything else is a clue.
| What you notice | Likely bearing problem | What to do |
|---|---|---|
| Wheel spins smooth but sounds gritty | Dirt or sand inside the races | Clean and re-oil, then re-test |
| Notchy or "clicky" feel when turned slowly | Debris or a damaged race | Clean once; replace if it is still notchy |
| High-pitched squeak | Lubricant washed out | Re-oil (one or two drops) |
| Rust on the outer race, milky grease | Water got in | Clean and re-lube; replace if pitted |
| Car pulls to one side with trim and toe set right | A seized or dragging bearing | Find it by spinning each wheel; replace it |
| Torn, dented or missing seal | Seal damage | Replace. No cleaning fixes that |
The spin test, step by step
- Battery out first. Always. Then remove the wheel nut and wheel.
- Turn the axle slowly between your fingers. Feel for notches, grinding or tight spots.
- Flick it faster and listen. Gritty means dirt. Crunching usually means sand inside the races. A squeal means the oil is gone.
- Wiggle it. A little play is normal. Clunking or visible wobble means a worn bearing or a hub that has worn oversize.
- Look at the seals. Dented, torn or missing seals mean that bearing is going in the trash.
The "pulls to one side" clue
RC Car Action notes that a car that pulls even with the steering trim and toe set correctly may have a seized bearing. A locked bearing makes the axle spin inside the bearing's inner race, or the bearing spin in the hub, and that friction makes heat. Plastic hub carriers do not like heat. If one wheel is noticeably harder to turn than its partner on the other side, start there.
When to check them
Do a quick spin test after any run in water, mud, snow or loose sand, and every few weeks for normal bashing. Wheel hubs and axle carriers take the most abuse because they sit right next to the dirt. Bearings deeper in the transmission and diffs are more protected, so check those when you have the gearbox open anyway.
2. How to Clean and Re-oil RC Bearings
Cleaning makes sense when a bearing still spins freely but feels gritty. If it is notchy after a good cleaning, the race is damaged and no amount of solvent will fix it. Here is the process RC Car Action and FMS Hobby both describe, with our bench notes added.
Get them out without wrecking them
Do not hammer bearings out. Press evenly on the outer ring with the largest tool that fits, or slide the axle partway in and wiggle the bearing loose. RC Car Action warns that too much force can permanently damage a bearing. If you must push from the inside, push on the metal rings, not on the seal.
The cleaning procedure
- Wipe the outside with a rag and a shot of motor spray so you are not pushing dirt in when you open it.
- Lift the rubber seal on 2RS bearings: slide a hobby blade under the inner edge of the colored seal and work around slowly without cutting it. Metal shields are a different story; see below.
- Flush with solvent. Motor spray works well. FMS also lists brake cleaner and high-percentage isopropyl alcohol. Spin and flush again until the solvent runs clear and the bearing feels smooth.
- Never use soap and water. FMS warns that leftover moisture speeds up rust, and RC Car Action says never to use a water-based cleaner on bearings.
- Dry with compressed air while holding the inner race. FMS warns that spinning a dry, unlubricated bearing at high RPM with compressed air can score the balls.
- Re-oil with one or two drops of light bearing oil, spin to spread it, then press the seal back until it snaps into place.
Metal-shielded bearings
Shielded bearings (the shiny metal covers) are harder to open without damage, and FMS treats them as replaceable. RC Car Action's method is to shake them in a sealed container of solvent, swap in fresh solvent when it gets dirty and repeat, then drip oil in while spinning the bearing on its axle. It works for a quick refresh, but in a basher we would rather swap to rubber-sealed bearings.
Oil or grease?
Light bearing oil gives the least drag but washes out fast in wet conditions. RC Car Action does not recommend grease for RC bearings because dirt sticks to it easily. The exception is a crawler or trail rig that sits in water: FMS suggests marine grease, packed to only about a third of the bearing's inside space, because overfilling pushes grease past the seals.
3. How to Size, Choose and Replace RC Bearings
Sometimes cleaning is a waste of an evening. FMS Hobby lists the replace-it signs: grittiness that stays after cleaning and drying, pitting or heavy rust after solvent, and torn or warped seals. When a truck needs a lot of bearings, a fresh set can also be faster than cleaning each one.
Reading bearing sizes
RC bearings are sold by three numbers in millimeters: inner diameter x outer diameter x width. So a 5x11x4 bearing has a 5 mm bore, an 11 mm outside diameter and is 4 mm wide. Check your exploded view in the manual, or measure the old bearing with calipers. Sizes like 5x10x4 and 5x11x4 look almost identical in your hand but are not interchangeable, so measure twice.
2RS vs ZZ: which to buy
A 2RS bearing has rubber seals on both sides; ZZ means metal shields on both sides. NRB Bearings explains the trade-off: rubber seals touch the inner ring, so they block dust and moisture better but add a little friction and limit top RPM. Metal shields do not touch, so they spin freer but only stop larger particles. For bashers that see dirt, grass and puddles, rubber-sealed is the right call.
Installing the new ones
- Clean out the hub or carrier bore so there is no grit left in there.
- Press the bearing in square, pushing on the outer ring. It should seat flush without forcing.
- Replace both bearings in a hub at the same time. If one died from water, its neighbor saw the same water.
- Reinstall the wheel and snug the nut until the play is gone, then stop. An overtightened wheel nut preloads the bearings and adds drag.
- Spin-test again. New bearings should be quiet and free.
Aftercare that makes them last
After wet runs, Traxxas recommends drying the vehicle and spraying a rust inhibitor such as WD-40 on exposed bearings and drive cups, then letting it finish drying somewhere warm (Traxxas cleaning guide). That five-minute habit saves more bearings than any upgrade.
Conclusion
Bearings are a maintenance item, not an upgrade. Spin-test them after rough runs, clean the gritty ones, replace the notchy or rusty ones, and buy rubber-sealed bearings in the exact size your manual lists. Do that and you will stop finding melted hub carriers, and your truck will roll straighter and run a little cooler.
Not sure what size you need or which bearing is making the noise? Bring the truck to our Cumming showroom and the repair bench will help you sort it out. You can also browse our bearings, the Traxxas 4x4 parts we stock, or contact the shop to check a part number before you order.
Gear Mentioned in This Guide
Traxxas Rubber-Sealed Ball Bearings 8x16x5mm (5118)
Rubber-sealed 8x16x5mm bearings that Traxxas lists for the Rustler 4X4, Slash 4X4 and Stampede 4X4, among others.
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Traxxas Ball Bearing 5x11x4mm (5116)
A blue rubber-sealed 5x11x4mm pair used across many Traxxas models.
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Traxxas Ball Bearings 6x12x4mm (5117)
Another size from the Traxxas 4x4 platform. Measure yours or check your exploded view before you order.
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5x10x4 Rubber-Sealed Bearings MR105-2RS (10 pack)
A 10-pack of 2RS bearings, handy when a whole corner needs refreshing.
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Pro Boat Marine Grease, 5 oz
Water-resistant grease for crawler and wet-weather bearings. Use a little.
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Traxxas Speed Bit Master Set (8710)
Hex and nut drivers for pulling hubs and carriers without stripping anything.
Shop nowFrequently Asked Questions
How do I know if my RC car bearings are bad?
Take the wheel off and spin the axle by hand. A good bearing turns smoothly and quietly. Grit or a gritty sound means it needs cleaning. A notchy feel that stays after cleaning, rust, pitting or a torn seal means replace it. A car that pulls to one side with the steering set up correctly can also point to a seized bearing.
What should I use to clean RC bearings?
Motor spray is the usual choice. Brake cleaner or high-percentage isopropyl alcohol also work. Do not use soap and water, because moisture left inside causes rust. Dry with compressed air while holding the inner race, then add one or two drops of light bearing oil.
Should I oil or grease RC car bearings?
For most cars and trucks, use light bearing oil. It has less drag, and grease tends to collect dirt. For crawlers and trail trucks that go through standing water, marine grease holds up better. Fill only about a third of the bearing so it does not push past the seals.
What do the numbers on RC bearings mean?
They are millimeters: inner diameter x outer diameter x width. A 5x11x4 bearing has a 5 mm bore, an 11 mm outside diameter and a 4 mm width. Match all three numbers when you buy replacements.
Are rubber-sealed or metal-shielded bearings better?
For bashing, rubber-sealed (2RS) bearings are better because the seals keep out dirt and water. Metal-shielded (ZZ) bearings spin with slightly less friction but only block larger particles, so they suit clean surfaces more than dirt and mud.
How often should I replace RC bearings?
There is no set schedule. Check them after wet or sandy runs and every few weeks of regular use. Replace any bearing that stays rough after cleaning or shows rust, pitting or a damaged seal. When one wheel bearing fails from water, replace its partner in the same hub too.
