Crawler Bearings vs Bushings: How to Tell What You Have and Whether to Upgrade

I spent a few weeks assuming the slight drag I felt when I spun my crawler’s wheels by hand was just how small RC trucks are. Then someone at a trail meetup spun one of his and it kept coasting for a second after he let go. Mine stopped almost immediately.

The difference was bearings. His truck had them and mine, in that particular spot, did not.

This is one of those upgrades that gets recommended constantly without anyone explaining what it does or whether you already have it. So here is the version I wish I had read first, including the part where I tell you that for a lot of people this upgrade changes very little.

Bushings and Bearings, Plainly

A bushing is a solid sleeve. The axle shaft passes through it and slides against the inside surface as it turns. It is cheap, it is durable, and it works. It also produces sliding friction, which is the kind you feel as drag.

A ball bearing is a small assembly: an inner ring, an outer ring, and a set of steel balls between them. The shaft turns the inner ring, the balls roll, and the outer ring stays put in the hub. Rolling friction is much lower than sliding friction. That is the entire pitch.

Both do the same job of supporting a spinning shaft. One does it with less resistance and costs more.

What Actually Ships in Your Rig

Here is where most advice online falls apart. People will confidently tell you that “the SCX24 comes with bushings” or “it comes with bearings,” and both statements have been true at different times.

Axial has shipped the SCX24 in a lot of variants across several years, and what is in the axles and transmission has not been consistent. Some trims and some production runs use bearings in places where others use bushings. The box does not always tell you, and product listings for the truck often copy specs from an older version.

The TRX4M generally ships with ball bearings in the drivetrain, and that is part of what the higher price buys you. But “generally” is doing real work in that sentence, and a truck that has been driven hard by a previous owner can have bearings that are technically present and functionally dead.

So do not buy a kit based on what someone on a forum said about a truck that looks like yours. Spend five minutes and look.

How to Check in Five Minutes

Pull one front wheel. The hex driver that came in the box will do it. Slide the wheel off the axle stub and look at the piece the shaft passes through.

A bushing looks like a plain metal sleeve with a smooth bore. Nothing moves inside it. A bearing has a visible seam between two rings, usually with a rubber or metal shield over the face, and if it is an open bearing you will see the balls.

Then do the spin test. With the wheel off and the truck sitting in neutral, spin the axle by hand. Bushings feel slightly draggy in a consistent, even way. Good bearings spin freely and quietly and coast a little before stopping.

There is a third result worth knowing: rough, gritty, or notchy. That is a bearing that has been contaminated or has started to rust. That is not a “should I upgrade” question. That is a worn part, and it will keep getting worse.

What a Bearing Kit Actually Buys You

Being honest about this matters, because bearing kits get sold as a performance upgrade and they mostly are not one.

What you get is less drivetrain drag. In practice that shows up as wheels that spin more freely, a motor that has slightly less work to do, and runtime that improves by a modest amount rather than a dramatic one. On a rig that already runs warm, less parasitic drag is a real if unglamorous benefit.

What you do not get is climbing ability. Bearings will not stop your truck tipping over, will not add traction, and will not fix a line you keep failing. If stability is the problem, brass weight and better tires are where the money goes, and it is not close. The first five upgrades guide covers that ordering in detail, and bearings are deliberately not at the top of it.

The honest summary: if you have bushings, a bearing kit is a cheap, satisfying, low-risk improvement that makes the truck feel nicer to drive. If you already have healthy bearings everywhere, buying a kit does nothing at all. Check first.

Where Bearings Matter Most

If you are only replacing some locations, do them in this order.

Wheel hubs first. These carry the most load, see the most dirt and water, and are the easiest to reach. They are also where you will feel the difference most clearly when you do the spin test afterward.

Transmission next. Reducing drag close to the motor means the motor works less for the same wheel speed. This is the location where a bearing swap has the clearest effect on heat and runtime.

Everything else last. Steering knuckles and various pivot points can take bearings on some builds, and the gain gets small quickly. This is where diminishing returns start.

The Half Nobody Mentions

Bearings are consumables. That is the trade you make when you install them.

A bushing tolerates grit reasonably well and gets slowly worse. A bearing packed with fine dirt or left wet goes from smooth to gritty to rusted, and once the race is pitted, cleaning it does not bring it back. Micro crawler bearings are small, which means small amounts of contamination matter more than they would on a larger truck.

The fix is not exotic. Dry the truck properly after wet runs, blow the chassis out, and spin each wheel by hand every few sessions to listen for roughness before it becomes a replacement. If you do not already have a routine for this, the maintenance routine I actually follow is the logical next step after fitting bearings, because the install is the easy part and keeping them alive is the part that decides whether the upgrade was worth it. If you run in creeks or snow, driving in water and snow covers the drying process in more depth, and water is the fastest way to ruin a fresh set.

What to Buy

Buy a kit sold specifically for your platform. Bearing sizes differ between the SCX24 and the TRX4M, and occasionally between versions of the same truck, so a generic assortment usually leaves you short one size and holding four you cannot use. SCX24 bearing kits and TRX4M bearing kits both run in the ten to twenty dollar range for a full set from brands like Injora and Hobbypark.

Choose sealed bearings rather than open ones. Open bearings spin marginally more freely on a bench, and that advantage is meaningless at crawling speed. Keeping dirt out is worth far more.

You do not need special tools for this on a micro crawler. A hex driver set, patience, and something small and blunt to press the bearing in square is enough. If your driver set is the one that came in the box, the essential tools guide covers what is actually worth replacing it with, since stripped screws cost more than the bearings do.

One last thing worth saying out loud: replace one location at a time. It gives you a reference for how the part came out, and if something does not fit right you know exactly which step to revisit.

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See also: Your First 5 Crawler Upgrades · Cleaning and Maintenance · Essential Tools · Driving in Water and Snow · SCX24 Platform Guide · TRX4M Platform Guide

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