Replacing cartridge bearings

(Not as simple as it seems)

Extralite hubs employ beefier bearings than the majority of our famous competitors.
Bigger bearings are mounted onto axles of a bigger diameter. This creates a stiffer assembly that significantly increases bearing durability.
Our MTB hubs feature also additional external seals to keep moisture and dust far from the 2RS bearing seals.

Read well these info before ordering new bearings.
Bearing replacement is not an easy operation as it may seem.
Here below you'll find the basics on how to manage properly a cartridge bearing.
If you simply pop in a set of new bearings chanches are that they get damaged right from the start.
Additionally the installation of any kind of Hybrid & Ceramic bearings requires a really good specific expertise.
If your hub was originally equipped with standard bearings it will probably require micro-tolerance adjustments to axle and bearing fittings,
this to allow proper bearing rotation and durability (but these operations are for real experts only).
Alternatively send your hub to us for a proper servicing.


Extralite's Factory Installed Bearing Options

See here pro and cons for each type.


Removing a Worn-out Bearing
In most cases, when you have to extract a hub bearing, you can only push it out from its internal race.
This operation will generally damage or compromise the bearing races, however, if you are going to replace a worn-out bearing with a new one, this is a marginal problem.

Removing a Bearing that's Still Good
In case you wish to re-install a previously-used bearing you'll need to extract it in a safer way. Avoid hitting the internal race with a mallet at all. Even a threaded extractor or a bench-press can damage the bearing races.
Try to warm up the hub-shell with a hairdryer to facilitate an easier extraction of the bearing. The heat expands the alloy hubshell more than the bearing steel allowing to gently push it out by hand pressure and will also soften
Loctite (or other coaxial glue) that could have been eventually applied at the factory original assembling.

Inserting a New Bearing
A new bearing should always be inserted by pressing it on the same race that's going to be pressed into the hub fitting.
Cartridge bearings are generally fitted into the hub-shell with some interference on the outer bearing race, these cases apply pressure on the bearing external race only.
Note that the pressure should be applied exclusively onto the outer race, do not push flat on both races.
Pressure or hits on the bearing's internal race will permanently damage the balls and races of your new bearing.
To properly press in new bearings are normally used specific insertion tools (each bearing size needs its specific insertion tool). Use only an inserting tool that is made for your exact bearing size.
Extralite offers complete tool-sets for hub maintenance: the Pro-tool kit 1 and Bearing-sitter includes bearing inserting tools in every bearing sizes used on UltraHubs / HyperHubs / CyberHubs.

Using an Old Bearing to Protect the New One
tAs a last resort, in absence of proper inserting tools, you could use the old bearing to carefully press in the new one as follows (use this method for emergency only)
- the 2 bearings should be perfectly aligned
- the mallet should hit only the external race of the worn bearing
- tap the bearing down in small increments and periodically make sure it's getting in perfectly flat.
- make sure the cartridge has reached it's final position contacting the bore end-shoulder, than do not over press.

Axle insertion
As your new bearings are finally in their correct position rmemind that the hub axle has to slide into the bearings with only a mild pressure (the pressure amount is directly related to the bearing side-load capacity).
Forcing the axle through the bearings can again permanently damage balls and races of the new bearings.

Hub-Shell / Cartridge Bearing Interference Criteria
As general rule the pressing interference between hub-shell and bearing should be around 0.01mm. An interference of 0.02mm applied on a thin bearing (ex. 6802 - 6803 etc.) can compromise the ball-races tolerance.
On high quality bearings the matching/coupling of the parts leaves less than 0.003mm of play between races and balls before the installation.
If the races get pressed by a excessive pressure of the fitting bore or by the axle the balls will rub against their races and won't rotate smoothly and this brings to premature wear too.
The opposite case of a slightly loose bearing fitting can generally be properly dealt using Loxeal 83.21 / Loctite 260 or equivalent "coaxial coupling" products; bearing removal will require to warm it up to 60° with an hair-dryer.

Hybrid Ceramic Bearings
The installation of ceramic bearings is rather difficult and requires a very good specific expertise. These expensive bearings require an even more precise tolerance match.
A proper bearing and axle insertion is critical when you are planning to mount hybrid-ceramic bearings. The ceramic balls feature a very hard surface that can ding the steel races very easily. Excessive interference of the bearing outer-race with its hub shell fitting will often result in a rough-rolling bearing. The same happens when the axle requires too much pressure to be slid into the bearing's inner-race. Both these conditions compromise bearing effectiveness and durability right from the start.

Note: If your hub was originally equipped with standard bearings axle and bearing fittings will probably require micro adjustments of their fitting tolerances to allow proper bearing rotation and durability (these operations are for real experts only).
Alternatively send your hub to us for this servicing.

Seals Stiction
Bearing seals are often the first resposable of bearing durability.
Tighter seals increase friction however do not over-estimate that effect, here is why: rubber seals beak-in and seat quite rapidly, so wait before judging. Additionally note that the effective bearing friction shouldn't be judged simply rotating the axle with your fingers, that shows only seals and grease stiction. Don't get excited by silly advertising of a bearing that spins for minutes in seller's hand, that's the effect of absent lubricant and non effective seals (bullshit). Good seals are a must for any smooth and durable bearing.

Raeal Friction under use
In the real world bearings get highly loaded by chain-pull, rider weight etc. and that's the cause of a real friction. When the bearing spins its balls rotate under load, but balls are also forced to slightly rub between races. This causes a much greater friction than a properly-fitted protective seal that helps keeping your bearings clean and smooth for a longer time. This is the reason why harder races with quality ceramic balls offer a performance advantage over others.

Bearing Durability
A quality Abec-5 steel bearing mounted on any Road Extralite hub can last for a really long mileage, we have serviced several properly kept hubsets with over 40.000Km of usage with their original bearings still in good conditions.
Bearing durability is related to a great number of factors such as seal type and their conditions, bike washing mode and frequency, bike use and environment, hub maintenance and more. All that makes each individual case quite different.
However note that water and moisture left inside any bearing after bike washing will soon start to corrode the bearing races of any steel or hybrid-ceramic bearing if the bike get parked and not used again for days or weeks. Keep this simple rule well in mind!
The only exceptions to the above happen with fully stainless bearings and XD-15 bearings. In highly corrosive environments the XD-15 ceramic balls resist to corrosion and help to clean their races that are made with an extremely hard non-corrodible steel.

Ceramic Bearings

Bearing Friction
Bearing friction should be judged under load when the balls rub and rotate between races. In these circumsances the use of hybrid ceramic bearings can offer an advantage.

Today’s Quality Standards
Hi-end bearing manufacturers have now acheived much higher quality standards than only few years ago. Quality hybrid ceramic bearings are now made with incredibly hard steel races that can survive the coupling with ceramic balls for a much longer life.

The latest generations of hybrid-ceramic bearings, such as ABI Zero and HDC, offer durability comparable to a steel unit. Earlier generations of bearings could only offer a fraction of the durability of a regular steel bearing.
In highly corrosive environments the ceramic ball resists corrosion and helps to clean the hard steel races. In such circumstances the overall durability could be even higher than steel bearings, however this is generally an uncommon situation

Advantages and Disadvantages

Do not over-estimate the advantages of hybrid ceramic bearings. Their durability is equal or lower than steel ones, price is higher,all to gain a slightly lower rolling resistance.
When you are choosing to use hybrid-ceramic bearings be aware that the lower rolling resistance is the sole advantage they can offer besides a very very slight weight reduction (ca 1gr. less on each hub bearing).

Beware of Cheap Gimmicks

To enhance the feel of low-rolling resistance some non-serious manufacturer equip their bearings with non-contact seals and you can see them spinning for minutes, that's just for fun; an absolute fake.
Those bearings in reality last only few rides, as they collect dirt directly into their ball races and shortly thereafter require replacement (no surprise)

Full-ceramic Bearings
Among bike enthusiasts have tried to employ full-ceramic bearings in order to save weight and further reduce rolling resistance. Unfortunately with today's technology a properly dimensioned steel bearing cannot be replaced with a full-ceramic bearing of the same dimensions. Size should increase commensurately when moving from steel to ceramic and this nullifies any weight savings and requires a specifically designed hub-shell.
Additional note: even full-ceramic bearing manufacturers are openly not recommending their products for bicycle applications due to the ceramic material's fragility. Typical bicycle applications involve high impact resistance at low rpm (10-100 rpm) while the typical full-ceramic bearing application is at very high rpm (over 20,000 rpm) and absorbs only low impacts.

Load ratings of ceramics bearings
Ceramic has a modulus of elasticity higher than that of high carbon chrome bearing steel.
In the ceramic bearing, therefore, less deformation on the rolling elements (balls or rollers) generates higher stress at the contact point between the rolling element and raceway, when compared to a steel bearing.

Therefore, the contact stress between rolling elements and races of ceramic bearing would be significantly higher than that of steel bearing, under the same amount of load.

Bearing type
Dynamic load
Impact load
Hybrid ceramic
ca. 80% of steel bearing
ca. 70% of steel bearing
Full ceramic
ca. 80% of steel bearing
ca. 20% of steel bearing

Load ratings of ceramic bearings compared to steel bearings.

The load capacity of ceramic bearings is accordingly decreasing when working temperature is increasing. HSC suggests choosing a larger load rating capacity bearing when using a full ceramic bearing for your application. Due to the brittleness of ceramics, full ceramic bearings are not capable of withstanding too much impact load. The outer races or inner races will generate cracks or even suddenly break under a certain amount of impact load.