Inline Skates Parts Descriptions

Wheels
  In-line skating wheels are usually made from polyurethane, with different thickness and hardness. Recreational skates usually come equipped with 70-72 mm wheels for a better center of gravity. You can go up to 72-76 or a 80 mm for more speed if the skates track will accommodate them. Hockey wheels are smaller and may be more tapered for better turning. Aggressive wheels are usually 55-67 mm and are the smallest and hardest, to stand up to all the grinding and jumping. Racing wheels are the thinnest for more speed but allot less stability.

Wheels Hardness
  Wheel hardness is measured in durometers. Lower numbers mean a softer wheel and higher numbers mean a harder wheel. You can recognize the durometer because it is followed by the letter A (example - 78A) (pic #1). The average recreational wheel is 78A or 82A. Softer wheels are for a lighter ride and a better grip when turning, but are a bit slower. Harder wheels are faster, but may even slip in a sharper turn.

Frames
  Most frames nowadays are made of aluminum alloy or nylon and fiberglass composites. Aluminum frames are stiffer, faster, and lighter, but are usually more expensive (pic #2).

Bearings
  Most bearings have an ABEC rating (Annular Bearing Engineers' Committee). Supposedly, the higher the rating, the better the performance and speed. They are usually ABEC-1, ABEC-3 (pic #2), ABEC-5, or even ABEC-7 at the extreme end. Does ABEC affect the speed of your skates? Not likely, unless you are skating at 330 mph that is. Speed is affected first and foremost by your choice of lubricant
  You can get serviceable or non-serviceable bearings. The serviceable ones have a shield with a removable "C" ring, or it may be removable on it's own. These are the ones you can take apart. (check our cleaning bearings tutorials) The non-serviceable ones have a shield that cannot be removed. You only have to wipe these ones off, or replace them.  
  Never lubricate the outside of bearings because the dirt will stick to them and that slows you down.

Rockering
 This is an option on most recreational skates if you look for it. What a rocker does, is drop the two middle wheels a little further down than the two outside wheels. This is to make turning quicker and sharper. Most Hockey skates are automatically rockered. You can usually find the switch or plastic holder on the frame somewhere, most likely in the center of the boot area (pic #4).