The advances in tyre, suspension, and frame technology have enabled mountain bikers to ride increasingly daring trails, and better riding apparel allows riders to ride throughout winter. That creates increased wear potential on bearings. Moisture and grit seepage from riding through the winter can trigger bearing corrosion. This makes knowing how to replace hub bearings a valuable home mechanic skill.

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The two bearing types 

Mountain bike hubs feature two bearing configurations: cup and cone, and sealed cartridge. With cup and cone bearings, you have direct access to the individual ball bearings once you’ve opened the hub. That gives you the option of removing bearings, cleaning, and regreasing. Cup and cone bearings can come in cages or as loose balls.

Sealed cartridge bearings feature on most high-end hubs, and true to their name, the bearings are encased in grease and sealed. With these, you don’t deal with the individual exposed bearings but replace the entire sealed cartridge that contains them, if the bearings are worn or corroded. 

Before you start with the hubs

Once you’ve removed the wheels, also remove the brake rotors. There’s nothing worse than inadvertently bending or contaminating a brake rotor when you’re working on hubs. If you’re working on the rear wheel, the cassette must be removed. 

Use the chain whip tool to get a grip on the cassette and engage its lockring with the splined tool specific to your cassette. Turn counterclockwise to disengage the lockring. Don’t be alarmed – it makes quite a loud sound as it’s loosening. Slide off the cassette stack. 

That said, some hub systems on the market don't require tools to remove the freehub, thus the cassette can stay in place as the freehub is pulled from the main hub body.

Tools you need for a cup and cone hub-bearing service 

The tools needed include cone spanners, an adjustable spanner, and a magnetic hex screwdriver. Cleaning items to have ready are grease, degreaser, paper cloths and dependable all-purpose rags. 

1. Remove the cones

To access the cup and cone bearings, you'll need to loosen the locknut. Attach a cone spanner to the cone, and then a regular spanner to the nut for undoing. Once the primary fastening tension is released, gently unscrew everything by hand and remove the axle. 

2. Removing the bearings

Getting the individual ball bearings out of a cup and cone hub requires dexterity and the correct tools. You don’t want to spill them onto your garage floor and have to search for bearings, which love to roll and come to rest in the hardest-to-reach places. A magnetic tip screwdriver does the job splendidly, allowing you to pluck the bearings out of the race without spilling them. 

3. Inspect and clean the bearings

Cup and cone bearings that have developed some play and signs of wear usually need a mere regrease. Use a degreaser and a paper towel to clean the bearings. Once they are clean, visually inspect them for surface wear or corrosion. If they look good, they can go back in. Before repacking those bearings, you can clean the race and apply new grease. 

If you suspect the wear is more pronounced, with bearings mechanically worn, you’ll need to discard them. And replace them with new bearings. 

4. Reassemble and set the preload

With your cleaned or new bearings ready to be reinstalled, you can grease the hub races before using the magnetic screwdriver to pack the individual bearings into place. 
Slide in the axle, pressing it against the bearings, to confirm it’s seated properly.

Now you can start reassembling the hub by hand tightening the cone on the non-drive side until it meets the bearings.

Check the axle rotation for smoothness and tug it a touch, to see if there’s any play. If there is, try another incremental tightening of the cone. 

5. Tighten it all up

If you are happy with the axle’s spinning and lateral stability, you can add all the fasteners you dissembled initially. Reversing the order. 

Be sure not to overtighten the locking nut when making the final adjustment. It’s annoying having freshly serviced bearings and an overtightened hub that’s not spinning freely. 

What if the cups are worn?

Although cup-and-cone bearings have a proven mechanical design and are known for durability and simplicity, you'll probably need a new hub once wear has spread to the cups. 

Shimano’s cup and cone hubs are rather ubiquitous, especially among entry-level and value mountain bikes. Once the cups on these hubs are worn, they can’t be replaced. This is another argument favouring preventable maintenance, which can keep cup-and-cone hubs spinning for decades. 

Servicing sealed bearings

This is the configuration for most mid- to high-performance hubs. Sealed bearings require a bit more skill and tools to service, but it’s still well within the ability of a home mechanic with some time to spare on a rainy weekend afternoon. 

The tool selection tallies several cone spanners (sizes 13 through 16mm), those trusty Allen keys, a soft mallet, bearing remover, grease and a bearing press tool, which is a great investment. Bearing press tools can also extract and set bearings on your dual-suspension mountain bike’s pivots, giving them multi-use adaptability. 

End caps come off in myriad ways

Sealed cartridge-bearing hub designs use several end cap fastenings on their sealed bearing designs. Depending on your mountain bike wheelset’s hub brand, you could get away with an easy tool-less removal with end caps that pull off by hand.

Some might require you to use a bit more force. That’s when the trusty vice clamp becomes handy. Place the wheel’s hub endcap in a vice and clamp it. Now place your hands on opposite ends of the rim to give you the best leverage when pulling. This should remove the hub end caps. 

Others require spanners to unscrew the caps. It's usually easy to remove the other by hand.

1. Remove the freehub (if servicing a rear wheel)

While not something you'll do on the front wheel, the rear wheel will have a freehub to contend with. Most often, freehubs can be removed by hand, simply by pulling it off the hub body. Many pawl-based freehubs have no extra parts to consider.

If you run a star-ratchet-driven freehub, there will be a pair of star ratchets and that'll come loose. Keep these in a safe place while replacing your hub bearings.

2. Remove the bearings

This is where the mallet comes into play. Sealed cartridge bearings need significant force to be dislodged. You want to place the wheel horizontally on a work table, with a section of tubing to support the hub flange. This gives you something to strike into for the bearings to dislodge and drop into. 

A Delrin tube is ideal for this. With the wheel correctly positioned, you can use an old axle or appropriately sized drift tool as the driver to force the bearings out. A few strong knocks with the rubber mallet might be required to dislodge your hub’s sealed bearing cartridges. Flip the wheel and repeat for the opposite side until both sealed bearing cartridges are removed. 

3. Clean and regrease

Using a degreaser and a rag, clean the whole hub of any old grease. Then, give the bearing races, bearings and areas on the axle where the bearings sit a coating of grease.

4. Replace the drive side bearing

There are two ways of fitting sealed cartridge bearings. One method foregoes a bearing press tool, where you can use a similarly sized old bearing as the driving tool, tapping the new sealed bearing cartridge into place with a mallet. Some patience and precision are required to avoid damaging the new bearing cartridge. A superior method is to use a bearing press tool. 

If you're using a bearing press, or a makeshift variant, assemble the press with the corresponding drifts and the correct bearing for that side of the hub – it's best to press one bearing in at a time for the best alignment and, if you're servicing a rear hub, it's best to start with the drive side bearing. Wind both handles of the press towards the hub, pressing in the bearing.

Assuming you're replacing a rear hub's bearings, setting the drive side bearing first is best as this is the side with the most axle showing from the hub – it'll be hard to find a drift that'll fit over this part of the axle.

5. Replace the non-drive side bearing

Once the bearing's in place, replace the axle and do the same with the non-drive side. However, as the axle is in place, you'll need to source a drift that can be used with a hammer that'll fit over the axle. A bearing press won't work here.

6. Reassemble the hub

All that needs to happen now is for everything to be reassembled. Apply a light lubricant to the freehub engagement teeth on the hub – a drop of dry chain lube will do. Pop any seals back in place, and return the freehub (a bit of string around the pawls pull them down so the freehub can slide back properly) that string can be pulled out when needed. Put the drive side end cap back.

Give the freehub body a fresh coat of grease before putting the cassette back in place. It's also good to clean and regrease any thru-axles.

Note - When servicing the rear hub, check the bearings inside the freehub (the bit the cassette sits on). If it feels rough or the freehub is binding (you'll know if it is when you roll the bike forward and the pedals rotate at the same time), you'll need to replace the freehub bearings. A freehub bearing service is an identical process to a wheel hub service but a bearing press will cover the whole job.

Why a bearing press is worth it

Suppose you’re anxious about misalignment and the damage these can cause when replacing sealed bearing cartridges on your hubs. In that case, the bearing press is one of those application-specific tools that can make even the most amateur home mechanic feel like a slickly skilled pro. This is a tool for life that you’ll use every season. 

A bearing press tool has several drift sizes to match against the bearing you need to press back into place – or press out. It’s easy to align and explicitly designed to press sealed cartridge bearings back into place, so you cannot get it wrong when using one.

How to identify bearings

Not every bearing is the same. Each has different inner and outer diameters as well as seal types. To find the bearings you need, each bearing has a bearing code moulded onto the seals and sometimes etched onto the outer race. 

For example, a 6903 LLU bearing is best used for a bike's pivots. 6903 is the bearing code that identifies the bearing variant, outer size and bore size where the 'LLU' denotes the seal type. An LLU seal is a medium contact, double lip seal that sits in grooves cut into the bearing's races.

When choosing your replacement bearings, find some with the same bearing code.

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