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Choosing skateboard wheel durometer
Durometer measures the skateboard wheel's hardness. Most manufacturers use the Durometer A Scale, which is a 100-point scale that quantifies how hard a wheel is. The higher the number, the harder the wheel. The average wheel durometer is 99a. Certain manufacturers may use the B Scale, which measures 20 points lower and allows the scale an extra 20 points for harder wheels. For example, an 80b durometer is the same hardness as a 100a durometer. Such skateboard wheels have a wider and more accurate hardness range.
Generally speaking, harder wheels are faster, and softer wheels are slower but offer more grip. Softer wheels are better suited to street skating; harder wheels are better for smooth surfaces, such as skate parks. Some companies even specially design their wheels for a specific use. For instance, Bones STF Formula and Spitfire F1 Street Burners are designed specifically for street terrain, while Bones SPF Formula and Spitfire F1 Park Burners are designed for park terrain.
Here are some general guidelines for wheel durometer.
Skateboard Wheel Durometer
78a-87a Soft wheel good for rough surfaces, longboards, or street boards that need lots of grip to easily roll over cracks and pebbles. Designed for smooth rides, cruising, longboards, hills, and rough surfaces.
88a-95a Slightly harder and faster with a little less grip, but the grip's still good. Good for street and rough surfaces.
96a-99a Nice speed and grip-- an all-around good wheel. Great for beginners skating street, skate parks, ramps,pools, and other smooth surfaces.
101a + Hardest and fastest wheel with the least grip. Ineffective on slick and rough surfaces. These are pro wheels.
83b-84b Wheels using the B scale are extremely hard, measuring 20 points lower than the the A Scale in order to allow the scale to extend another 20 points for harder wheels.