Skateboard speed relies on many aspects, the most important one is the RPM (revolution per minute) of the "Ball Bearings", the higher the RPM the higher the velocity you are skating. The ball bearing consist of inner race, outer race, balls, balls retainer and optional closures. As you may all know, any skateboard has 4 wheels (DUH), each wheel has 2 ball bearings, makes them all 8 Ball bearings, and they are (of course) sold as a set of 8 ball bearings. RPM of the ball bearings can be increased by reducing the friction between all the moving elements, here are the factors affecting the RPM:

1- Quality: The quality of any bearings are categorized by the "American Bearing Manufacturers Association" as ABEC rating, the more the ABEC rating the more precise they were made, the most common and good choice ABEC rating is ABEC-11.

2- Inner and Outer Race Material: Carbon, Chrome and Stainless steel are your options, I wouldn't choose anything but Chrome Steel, well .. it is the widest used bearings steel.

3- Balls material: Again the bottom line is to reduce friction, your options are (sorted best to "not bad") silicon nitride ceramic, Zirconia ceramic and steel.

4- Retainer material: Your options are (sorted best to "not bad") bakelite, nylon, bronze and steel.

5- Lubrication: I suggest just any multi-purpose oil, since a skateboarder can always take good care of his hardware, grease will make your wheels hard to free-spin

6- Closures: used to protect the moving parts of your ball bearings from outside contaminations. If you are skateboarding in a perfect environment (there is no such thing) with no dirt, no water and no humidity then you can always use your ball bearings without closures. Your options are (sorted best to "not bad") Teflon seals, metal shields, non-contact rubber seals, and contact rubber seals.

Confusing? .. Just search ebay for Skateboard Bearings and you will even learn more about what is new in the market, well... thanks to eBay; that was the way I learnt about skateboard bearings and became one of the sellers :)

irvineman