To start learning about longboard bearings, scope this amazing video from Rat Vision.
Skateboard and longboard bearings are built using five different parts. There are variations between these parts, which you can optimize for your specific application. Bearing balls, ball retainers, and closures (seals and shields) can all change slightly. The purpose for each part can help when choosing the right set based on price, speed, durability, and serviceability. Knowing the different parts involved can assist you in making a more informed decision when selecting your first or next set of bearings.
Skateboard Bearing Parts
- Seven or Six Balls (made from steel, titanium, or ceramic) - One Or Two Closures (aka shields) - Outer Ring (aka outer race) - Inner Ring (aka inner race) - Ball Retainer/Cage (aka bearing crown)
Just about every bearing out there has a slight variation from the next. However, with the exception of ceramic and/or six balls, these variations do not drastically affect the price. Price is usually determined by brand name, and the quality of material and manufacturing.
What's the ABEC Rating?
ABEC Ratings are a measure of tolerance. The governing body that sets forth bearing standards is called the Annular Bearing Engineering Committee, or ABEC (pronouced A-Bek). Tolerance is how precisely the components of the bearing fit together. A more precise fit between bearing parts makes for a more smooth and efficient bearing.
Please note that just because a bearing has a higher ABEC Rating does not mean it is faster. ABEC ratings are just one feature of a bearing. Other factors such as the strength of the components, the lubricants used, and the load on the bearing play a role in determining how fast the bearing can go. To imagine this, think of a bearing where all the components fit together flawlessly. If this bearing carries a load of a 500 pound rider, it will perform differently than when loaded with a 100 pound rider, or no rider at all. Additionally, if this bearing is made from steel it will perform differently than if made from plastic.
So What Does This Mean for Skateboarding?
ABEC Ratings were designed for industrial applications where bearings are being used in controlled environments. The actual measurements for ABEC tolerances are listed below. For scale, a human hair is roughly 0.180086mm thick.
- ABEC 1: 0.0075 mm (0.000295")
- ABEC 3: 0.0050 mm (0.000197")
- ABEC 5: 0.0035 mm (0.000138")
- ABEC 7: 0.0025 mm (0.000098")
- ABEC 9: 0.0012 mm (0.000047")
One little tiny piece of dirt in your bearing, in the most technical sense, will completely void the ABEC Rating. When buying a bearing for a skateboard, they should be purchased with the knowledge that they degrade immediately when the bearing is placed in the harsh skateboarding environment. Spending 2-4 times as much money for the ABEC 9 means you're spending cash on something that will almost immediately become void.
This being said, we are not telling you to go buy ABEC 1s. Absolutely not. Higher ABEC Rated bearings usually use better lubes and quality of materials. These kinds of things matter a lot for how the bearing will perform over time in the environment of skateboarding. Higher ABECs often mean a better bearing because they also use better lubes, materials, etc. However, do not make the mistake that it is better because of the ABEC Rating alone. An ABEC 9 from Company X could be completely different than an ABEC 9 from Company Z.
The term "Skate Rated" came from top companies trying to differential from the often misleading ABEC scale. Most top of the line bearing companies know that the ABEC scale is just one criteria in bearing selection and strive to get away from it. This is to avoid comparing their brand on par with another brand of equal ABEC. Top companies do things to their bearings to make them more ideal for skateboarding environments and this cannot be shown in an ABEC Rating.
Balls - Ceramic vs. Steel
Row, row, row your balls, gently down the inner race... Yep, the balls are the part of the bearing that do the rolling (surprised?). Because of this, they are arguably the most important piece of the bearing. Furthermore, balls land center stage for the hottest debate in longboard bearings: Ceramic or Steel? We'll put that to rest once and for all.
It is believed that ceramic balls are superior to the standard steel balls because they are stronger and smoother. Ceramic balls are significantly more expensive than steel balls, but this does not directly translate to a higher quality product.
There are 3 commonly used ceramics in ball bearings:
- Silicon Nitride (Si3N4)
- Zirconium Dioxide (ZrO2)
- Silicon Carbide (SiC)
Silicon Nitride ceramic is the hardest of the three and most often used in ceramic hybrid bearings. It's important to keep in mind that "ceramic" only refers to the balls. The races remain stainless steel, hence the term hybrid. Ceramics are not stronger than all steel balls, although the marketing headlines claim them to be. Ceramic balls are made from a ceramic powder, which is hardened on the ball surface. However, the center of the balls remains an unhardened ceramic powder. When a ceramic ball surface is compromised, the powder inside just falls apart.
Ceramic is brittle and does not handle vertical loads the way steel can. This can make their use in skateboarding seem somewhat impractical. However, the real test of a bearing is in its performance. In our experience, a high quality set of steel bearings is just as fast as a top of the line ceramic bearing. Sorry for killing the hype.
Ceramic Bearing Races
As we mentioned before, only the balls within the bearing are ceramic. The outer and inner races are still steel. While the ceramic balls might be "harder" and "invincible against rust", the steel races can get rusted and pitted. This will greatly affect the feel and performance of the bearing. Race surfaces come in direct contact with the ceramic balls, degrading what higher qualities the ceramic balls may have offered.
Steel is ductile and has elasticity that enables it to retain its original shape after loads are applied. The one advantage ceramic has over steel is resistance to corrosion, meaning rust. But, remember ceramic bearings are hybrids; therefore the inner and outer races are still susceptible to corrosion. Applications exist that specifically require ceramic bearings, but for skateboarding, we recommend saving your wallet and going with quality steel bearings.
Closures (Rubber Seals and Metal Shields)
Bearing closures are like walls that protect the bearing from outside debris, and help keep lubricants inside the bearing. Typically, skateboard bearings come with one closure, which is either a bunna rubber seal or metal shield. In rare occurrences, metal shields are replaced with plastic shields. There are 2 types of metal shields– pressed in non-removable metal shields, and removable metal shields held in with a C-ring. Pressed in shields do not allow for easy, if any, bearing maintenance.
Bunna rubber seals are considered a better choice for sealing lubricants in the bearing, and for not allowing contaminants, like dirt and moisture, to enter the bearing. There are two types of rubber seals. Located on the inside edge of the bearing seal is a thin flap of rubber. This flap is either lightly touching or not touching the inner ring of the bearing. These are known as "light contact rubber seals" or "non-contact rubber seals". Light contact rubber seals do a better job at protecting the bearing and keeping lubricant in. This light contact does not create any noticeable reduction in speed while skateboarding.
Removing Seals and Shields
Rubber seals and metal shields are known as closures and provide an important functionality, which is to keep bearings well lubricated and protected from contaminants (aka dirt n' shiz). There are three types of bearing closures that are featured on bearings. These closures are either rubber seals, metal shields, or non-removable metal shields.
We do not recommend following any trend that permanently removes seals and shields.
Metal shields and rubber seals dramatically increase bearing life and extend optimum performance. They help keep lubricants in and contaminants out. Once a bearing is exposed, its useful life will soon come to an end. So, why are the majority of bearings sold with only one shield or seal? Price. Higher quality bearings generally come with two shields.
One shield is almost like having half a raincoat. It leaves an opening on the side of each bearing that faces the inside of the skateboard wheel assembly. Sure, the wheel itself helps shield the bearing components, but keep in mind there is space between the skateboard truck axle and the bearings. They don't fit together super tightly. This space can allow contaminants to enter inside the wheel assembly. Once inside the wheel assembly, if bearing seals are not there to protect the bearings, contaminants will foul the bearings.This also means skateboard lubricants that allow proper functionality spill onto the truck axle.
We should also note that a minimal amount of contaminants and lubricant can get into or out of a skate bearing between a shield or seal and the inner ring. Bones and Dragon Bearings addressed this with their Labyrinth shielded bearings. However, even this solution cannot keep every piece of dirt out. Get used to it kids, skateboarding is a dirty business.
Wrapping up this section, you better know by now that bearing seals and shields are an important feature. We recommend riding bearings with two closures to ensure a longer bearing life, less maintenance, and higher performance.
Seal and Shield Codes
Below is a guide to inform you of the different codes seen on shields and seals. These codes represent the type of closure and the quantity (1 or 2).
Inner and Outer Races
The inner and outer races (aka inner and outer rings) are the tracks on which the balls roll on. These are almost always made out of steel. Races are kept together by the balls themselves, so it is important to note that bearings are not particularly well suited for side loads. When a side load is placed on the bearing, the inner and outer races want to separate. This creates pressures that can damage your balls and races. To combat this to some degree, we always recommend using bearing spacers.
Why Wheels Can Wobble
Why don't bearings and axles fit tightly together? It is because manufacturers of skateboard trucks and manufacturers of skate bearings don't use exact standards of precise measurement to create a tight fit. And why not? It's so there is no difficulty putting one company's bearings on another company's axles. The typical fit is relatively loose. Yep, this is kinda janky, but it is the best option for how many different choices out there. Again, this is why bearing spacers are always recommended.
Read more about why bearings spacers really matter.
Ball retainers are used to space out the balls evenly around the raceway. Nylon ball retainers can offer lower coefficient of friction than steel or brass retainers. Nylon retainers are better suited for speed, but are not as durable as metal retainers, which are better suited for the abuse brought on by street skating.
Pictured below are various types of ball retainers. The gold and silver in the top middle and top right are often called "cages" and usually cannot be removed easily. The other four pictured are often called "crowns" and can be removed easily.
Is it a Bearing Seal or a Ball Retainer?
The image below is to help with any confusion between a rubber seal and a ball retainer or cage. Sometimes people try to remove the ball retainer when cleaning. Removing the bearing ball retainer is unnecessary. Only the seal or shields needs to be removed during maintenance.
Questions? Join the discussion and throw a comment below!