Ever pulled apart your RC car for maintenance and found yourself staring at a tiny bearing wondering what "5x11x4" actually means? You're not alone. We see hobbyists at Hearns scratching their heads over bearing codes all the time, especially when they're trying to find replacements for their Traxxas or Arrma vehicles.

Here's the thing - those numbers aren't random. They're actually a pretty clever system that tells you everything you need to know about that bearing. Once you crack the code, finding the right replacement becomes dead simple. No more guessing games or buying the wrong size because the numbers looked similar.

Think of bearing numbers like a street address. Just as "123 Main Street" tells you exactly where to go, bearing codes like "6x13x5" give you the exact dimensions you need. The system's been around forever, and honestly, it works brilliantly once you get your head around it. Whether you're maintaining a basher that cops a beating every weekend or keeping a race car running smooth, understanding these numbers saves heaps of time and frustration.

In this guide, we'll decode the mystery of bearing numbers and show you when size really does matter for performance. From basic measurements to choosing between standard and ceramic options, we've got the practical info that'll help you keep your RC fleet rolling smooth. Plus, we'll share some tricks for identifying worn bearings before they cause bigger problems - because prevention's always cheaper than repairs.

Decoding the Numbers: What Each One Means

Right, let's crack this code. When you see something like "5x10x4" on a bearing or in a parts list, you're looking at three measurements in millimetres. Always in the same order: inner diameter x outer diameter x width. Simple as that. So a 5x10x4 bearing has a 5mm hole in the middle, measures 10mm across the outside, and is 4mm thick.

Some bearings get fancier with their numbering. You might see "MR105ZZ" or "688-2RS" on the actual bearing. Don't panic - these codes just add extra info about the bearing type and seals. The "MR" means miniature bearing, perfect for our Mini-Z cars. The "ZZ" tells you it's got metal shields on both sides, while "2RS" means rubber seals. Both keep the dirt out, but rubber seals do a better job at the cost of a tiny bit more friction.

Now here's where it gets interesting. That first number (inner diameter) needs to match your shaft or screw exactly. No wiggle room here - literally. Too big and your bearing rattles around uselessly. Too small and, well, it won't fit at all. The outer diameter needs to match whatever hole it sits in, whether that's in a hub, gearbox, or suspension arm. Get this wrong and you're in for a world of wobbles.

The width measurement often gets overlooked, but it matters more than you'd think. A bearing that's too wide might not let parts seat properly or could bind up your steering. Too narrow and it might not support the load properly, leading to premature wear. We've seen plenty of replacement bearings returned because someone grabbed a 5x10x3 when they needed a 5x10x4 - that one millimetre makes all the difference.

Types of RC Bearings and Their Uses

Not all bearings are created equal, and understanding the different types helps you pick the right one for each job. The basic ball bearing is what you'll find in most RC applications - steel balls running between an inner and outer race. Dead simple, reliable, and they do the job for 90% of what we need in hobby-grade vehicles.

Shielded bearings (marked ZZ) have metal shields that keep most dirt out while allowing them to spin super freely. These work great in clean environments or sealed gearboxes. But if you're bashing through dirt and mud with your off-road truck, you'll want rubber sealed bearings (2RS). They create a proper barrier against crud, though they do add a touch more resistance. It's a fair trade-off when you consider how much longer they last in harsh conditions.

Then there's flanged bearings - these clever little things have a lip on the outer race. Brilliant for applications where you need to locate the bearing precisely or prevent it from sliding through a hole. You'll often find these in drift car steering systems where precision is everything. The flange acts like a built-in washer, saving space and reducing parts count.

One-way bearings are the special forces of the bearing world. They spin freely in one direction but lock up going the other way. Essential for pull-start systems and some transmission designs. We don't see these as often in electric cars, but nitro guys know them well. And let's not forget thrust bearings - these handle loads pushing along the shaft rather than perpendicular to it. Critical in helicopter main shafts and some steering assemblies where you've got vertical loads to manage.

When Size Really Matters for Performance

Here's where things get proper interesting. Bearing size isn't just about making parts fit - it directly impacts how your RC performs. Larger bearings generally handle more load and last longer, but they're also heavier and create more rotating mass. It's all about finding the sweet spot for your application.

Take wheel bearings, for instance. A bigger bearing spreads the load over more balls and a larger contact area. This means less stress on each component, which translates to longer life and smoother operation. But go too big and you're adding unnecessary weight right where you don't want it - in the rotating assembly. Racing guys obsess over this stuff because every gram of rotating mass affects acceleration.

Smaller bearings in high-speed applications can actually be an advantage. Less mass means less centrifugal force trying to tear things apart at 50,000 RPM. This is why you'll see tiny bearings in brushless motors - they need to handle insane speeds while adding minimal resistance. But put those same tiny bearings in a steering knuckle and they'll be toast in no time.

Width plays a crucial role too. A wider bearing distributes side loads better, which is why you'll often see wider bearings in steering assemblies and suspension pivots. These areas cop lateral forces that would quickly destroy a narrow bearing. On the flip side, narrower bearings work fine in pure rotational applications like spur gear shafts where side loading is minimal. We stock bearing sets designed specifically for different applications because one size definitely doesn't fit all needs.

Quality Differences: Steel vs Ceramic

Now we're getting into the good stuff - the eternal debate of steel versus ceramic bearings. Steel bearings are the workhorses of the RC world. They're affordable, widely available, and honestly, perfectly adequate for most applications. A quality steel bearing from a reputable manufacturer will give you thousands of runs without issues.

But ceramic bearings? That's where things get fancy. The ceramic balls are harder, lighter, and smoother than steel. They generate less heat, resist corrosion, and can spin at higher speeds with less friction. Sounds perfect, right? Well, sorta. They're also significantly more expensive and can be more brittle under shock loads. Drop your car hard enough and a ceramic bearing might crack where a steel one would just deform a bit.

Hybrid bearings offer a middle ground - ceramic balls in steel races. You get most of the benefits of ceramic at a lower price point, plus better shock resistance. These are popular in racing applications where every bit of efficiency counts but full ceramic might be overkill. The ceramic balls reduce friction and heat, while the steel races handle the structural loads.

Here's the real talk though - unless you're chasing podiums or running extreme applications, quality steel bearings are probably all you need. The performance difference in a weekend basher is minimal compared to the cost difference. But if you're running a high-powered speed run car pushing the limits, or racing where hundredths of a second matter, ceramic or hybrid bearings can give you that edge. Just don't expect miracles - we're talking about small percentage improvements, not transformative changes.

Common RC Bearing Sizes by Vehicle Type

After years of helping customers find the right bearings, we've noticed clear patterns in what different RC vehicles typically use. Knowing these common sizes can save you heaps of time when ordering replacements or planning upgrades. Let's break it down by vehicle type.

1/10 scale touring cars and drift cars usually run 5x10x4 or 5x11x4 bearings in the wheels, with smaller 5x8x2.5 bearings in the steering assembly. The differentials often use 10x15x4 bearings, while the spur gear might have a 5x10x4 or 6x10x3. These cars prioritise smooth operation over ultimate durability, so bearing quality really shows in the performance.

Off-road vehicles like 1/8 scale buggies go bigger and beefier. You'll typically find 8x16x5 or even 10x19x5 bearings in high-stress areas. The extra size handles the abuse of jumps and rough terrain. Wheel bearings might be 12x18x4 or 13x19x4, giving that extra durability needed when landing hard. These vehicles often use more bearings too - sometimes 20+ throughout the chassis.

Rock crawlers present unique demands. They don't need high-speed capability but require bearings that can handle extreme angles and side loads. Common sizes include 5x11x4 for wheels and 8x12x3.5 for transmission components. Many crawlers use sealed bearings exclusively because they're constantly getting dunked in water and mud. The crawler bearing kits we stock reflect these specific needs.

Don't forget about the oddball sizes either. Steering servos often use tiny 3x6x2.5 or 4x7x2.5 bearings. Some motor cans take specific sizes like 7x11x3 or 8x12x4. European brands sometimes use metric sizes that seem random until you realise they're optimised for their specific designs. Always check your manual or measure the old bearings carefully - assuming won't end well.

Bearing Maintenance and Replacement

Alright, let's talk about keeping your bearings happy. The number one killer of RC bearings isn't wear - it's contamination. Dirt, sand, and water get past the seals and start grinding away at the balls and races. Once that process starts, it accelerates quickly. A bit of preventive maintenance goes a long way here.

For sealed bearings, your maintenance options are limited by design. You can't really clean inside them without destroying the seals. Best practice is to spin them regularly and listen. Smooth and quiet is good. Gritty or notchy means it's time for replacement. A drop of light oil on the seals can help keep them supple and sealing properly, but don't overdo it - excess oil just attracts dirt.

Shielded bearings offer more options. You can pop the metal shields off with a small pick or knife (carefully!) and actually clean inside. Soak them in degreaser, blow out with compressed air, then add a tiny drop of bearing oil. Some racers spend hours cleaning and oiling their bearings before events. Is it worth it? For racing, probably. For bashing, just run sealed bearings and replace when needed.

Now, when should you actually replace bearings? If they feel notchy when you spin them, they're done. If there's play when you wiggle the inner race, they're done. If they're noisy during runs, definitely done. Don't wait for complete failure - a seized bearing can take out gears, driveshafts, or worse. We keep plenty of replacement bearings in stock because they're essentially consumables in this hobby. Think of them like tyres - they wear out with use.

Upgrading Your Bearings: Worth It or Not?

So you're thinking about upgrading from the stock bearings. Smart move, or waste of money? Like most things in RC, it depends on what you're trying to achieve. Stock RTR bearings are usually pretty basic - they work, but they're built to a price point. Upgrading can definitely improve performance and longevity, but let's be realistic about the gains.

The biggest improvement comes from replacing bushings with ball bearings. Some budget entry-level cars still use plastic or brass bushings in less critical areas. Swapping these for proper bearings reduces friction dramatically and makes the whole drivetrain feel smoother. This is probably the best bang-for-buck upgrade you can do on a budget vehicle.

Moving from basic steel bearings to quality steel bearings is the next logical step. The difference between a no-name bearing and something from a reputable manufacturer is real. Better tolerances, smoother operation, and longer life. You might not feel a huge performance difference, but you'll definitely notice when you're not replacing bearings every few months. Quality bearings from brands like Fast Eddy or Boca Bearing pay for themselves in the long run.

The jump to ceramic or hybrid bearings really only makes sense for specific situations. Racing? Yeah, every little bit helps. Running a high-KV motor that spins at insane speeds? Ceramic bearings handle the heat better. But for general bashing or casual running, the cost isn't justified by the minimal gains. We've seen people spend $200 on ceramic bearings for a basher that gets run in dirt and sand - that money would've been better spent on a few sets of quality sealed steel bearings and maybe some proper tools.

Troubleshooting Bearing Problems

When your RC starts acting weird, bearings are often the culprit. But diagnosing which bearing is causing issues can be tricky. Let's run through the common symptoms and what they usually mean. Getting good at this saves you from the parts cannon approach - randomly replacing stuff hoping to fix the problem.

A grinding or rumbling noise that changes with speed usually points to a bad wheel bearing. Jack up each wheel and spin it by hand - the bad one will be obvious. Sometimes you can even feel the roughness through the tyre. If the noise only happens under load (driving but not on the stand), check the diff bearings. These take huge loads and often fail first in high-powered vehicles.

Excessive play or slop in the drivetrain often means worn bearings. Grab the wheel and try to rock it. Any movement at the hub indicates shot wheel bearings. Play in the spur gear or pinion suggests those bearings need attention. This kind of wear accelerates quickly because the misalignment causes uneven loading on gears and other bearings. Don't ignore it hoping it'll get better - it won't.

Temperature can tell you a lot too. After a run, carefully feel around the bearing locations. They should be warm but not hot. If one bearing area is significantly hotter than others, something's wrong. Could be contamination, lack of lubrication, or excessive preload. Over-tightened wheel nuts are a common cause - they compress the bearing and create excess friction. Same goes for diff bearings if the mesh is too tight.

Sometimes the problem isn't the bearing itself but what's around it. We've seen countless "bad bearings" that were actually caused by bent axles, worn bearing seats, or misaligned components. Before condemning a bearing, check that everything else is straight and true. A bent hinge pin will kill bearings quickly, as will an out-of-round bearing pocket. Having the right measuring tools helps diagnose these issues properly.