CUSCINETTI BRONSON SPEED CO DAVID GRAVETTE PRO BEARINGS G3 U

Skateboard bearings keep your wheels rolling one spin at a time. Skateboard bearings play a pivotal role in the functional performance of your skateboard. Bearings can be steel, ceramic, titanium or a combination of materials. These are mounted inside of the wheels and onto the truck’s axle. Generally, the higher the bearing’s abec rating, the longer they will last, thanks to the heightened “tolerance” rating it entails.

The abbreviation ABEC stands for "Annular Bearing Engineers Committee" and is a standard for how finely the rolling elements (this is what the balls in the bearing are called) are machined.
The higher the ABEC rating, the lower the fault tolerance in the manufacture of these components.

Since comparatively low speeds of the bearings are achieved during skating, the ABEC rating can be neglected. The full potential of the ABEC rating is not nearly exhausted when skating.
ABEC 7 or 9 bearings only develop their actual power at 20,000 - 30,000 revolutions per minute. With a 54 mm wheel this would correspond to a speed of over 200 km/h.

As the ABEC rating for skateboard bearings is of no real significance, manufacturers are increasingly moving away from the ABEC designation.
Bearings developed for skateboarding are now increasingly marked as "Skate-Rated".

BALLS
A set of six to seven balls roll freely along a track formed by the races and are held in place by the retainer.
The rotating and rolling balls are the crux of how the bearing works. Less balls means less friction and more speed.

INNER AND OUTER RING/RACES
The races form the track for the balls to roll, and also create the inner and outer walls of the bearing.

RETAINER
The retainer keeps the balls in place, equal distances from each other to reduce friction in increase strength.

SHIELDS
Shields cover the sides to help protect the balls from dust and debris. Some bearings have shields that are removable for easier cleaning.
Some have one or zero shields for reduced friction.

BEARING SPACERS
Some sets of bearings come with bearing spacers.
They are small cylindrical pieces that fit on the axle, between the bearings in the core of the wheel.
These spacers are meant to keep your bearings properly aligned and allow you to fully tighten your axle nut without restricting the spin of the wheel.
They are optional for most types of skating.
(TIP: If you want to powerslide on soft wheels, bearing spacers will reduce vibrations and make your slides much smoother and easier to control.)

STEEL
Steel bearings are the industry standard, and are both durable and economical. The quality of the steel can vary. Higher grade steel in premium bearings can make the bearing faster and more durable. The downside of steel is its tendency to rust when exposed to moisture. If you want your bearings to last, keep them well-oiled avoid rolling through puddles or skating in the rain. If you do get them wet, drop in some extra lube, keep rolling or put them by a heater to dry them quickly.

CERAMIC
Ceramic bearings are harder than steel and deform less when pressure is applied to them. Since they are also heat resistant, they expand less and create less friction at faster speeds. Another benefit is that they do not rust when exposed to moisture, making them great for cruisers and rain boards. The only downside to ceramic bearings is that ceramic itself is a brittle substance. The ceramic is susceptible to breaking if skated under high impact, meaning ceramic bearings are great for commuting and low impact skating, but not ideal for skating big gaps or stair sets.
TIP: While the balls in ceramic bearings cannot rust, the steel races still can. They’ll be more resilient, but you should still avoid water when possible.

TITANIUM
Titanium is lightweight, durable and highly rust resistant. Bearings made from titanium perform similar to steel bearings, but can last longer due to titanium's strength and resistance to corrosion. Like steel bearings, keep titanium bearings lubricated to reduce excess friction.