Indoor wheels are intended for smooth surfaces, and sometimes the only wheel permitted, on roller rinks. Indoor wheels grip the floor coating that the majority of rinks use. Indoor wheels are harder, this allows the skater to go faster on indoor surfaces. These wheels should not be used outdoors because they are so hard they will not be able to roll over pebbles, and other terrain surprises. The indoor wheel used outside could stop suddenly causing injury to the skater. Indoor wheels are available for recreational skaters, speed skaters, and artistic skaters.
Outdoor Wheels
Outdoor wheels are larger and softer than indoor wheels. This wheel will roll over most outdoor junk and absorb some of the bumps of the rough terrain. The most outdoor wheels are 60mm to 70mm in size and 76A to 82A hardness.
Hardness of the Wheels
There are two scales of measurements used to express the "hardness" or urethane - the "A" scale (used in skating with a range from a low of 70A to a high of 103A) and the "D" scale, which, if converted to skate wheels, would turn in lower numbers like 43D to 55D. The "A" scale is centigrade (100 degrees is boiling) - the "D" scale is Fahrenheit. Skate wheel manufacturer's use the "A" scale since 100+ is nearly the hardness of a porcelain sink by skate wheels standards. There is a dynamic and widely varying "practical" or performing" hardness is any skate wheel.
Factors affecting the practical or performing hardness of these wheels include:
- Temperature - Performance of a soft (70A) skate wheels on 120-degree asphalt outdoor will be different than on a 76-degree urethane floor coating while indoors.
- Profile (or Radius) - The profile of the wheels determines how much of the wheel is actually touching the ground (sometimes called the "footprint") and this effects the wheel's rolling resistance and grip. This gets tricky: A large hub can reduce a footprint on a high-speed turn. The narrow (or higher) the profile, the more it is suited to straight-line higher speed skating without a lot of twists and turns. Also, the narrower the wheel, (offering a thin "footprint" to the floor) the more easily maneuvered at lower speeds.
- Core- It secures the outer race of the bearings. The larger the hub, less urethane is used to complete the final diameter of the wheel. Hubs these days are made of exotic and durable nylons, zytels, and polycarbonate blends. The larger the hub, the lighter the wheel becomes and, in a dynamic way, the hub affects the point of contact on the floor surface. Larger hubs reduce potential roll-resistance, regardless of the profile.
- Size - The industry standard measures the diameter of the wheel in millimeters from the smaller (54mm - 2 1/8") to the taller (84mm - 3"). Taller wheels have more inertia to overcome when starting out, but sustain higher speeds for longer distances with less effort. Smaller wheels are better short-distance (or sprint) wheels since they offer faster acceleration (but without sustained roll) by being less resistant to quick starts and dashes than taller ones. In theory, a hockey goalie should be expected to use a wide profile (fat) wheel with the smallest diameter available since the longest distance the goalie travels in a game is merely a few feet in short bursts. A 22K long distance skater will have an advantage using the thinnest (just like a racing bike does) and the tallest wheel possible with the largest hub made blended with the skater's own rate of endurance
