The wheels of your skateboard can greatly affect your ride in numerous ways, such as the speed, your ability to take control of the skateboard’s movements, and what you feel while riding the board. The good news is that they come in various sizes, levels of durability, and colors, allowing you to pick one that suits your skateboard preference and style.
In 1982, while competing in the Rusty Harris contest in Whittier, California, Rodney Mullen debuted an ollie on flat ground, which he had adapted from Gelfand's vertical version by combining the motions of some of his existing tricks. Mullen used a "see-saw" motion, striking the tail of the board on the ground to lift the nose, and using the front foot to level the board in mid-air. While Mullen was not initially impressed with his flat ground ollie, and did not formally name it, he realized it opened up a second, elevated plane on which to perform tricks.
Just before a skater performs an ollie, there are three forces acting on the skateboard. One of these forces is the weight of the rider, shown here with two red arrows. Another is the force of gravity on the board itself, shown with a small black arrow. Finally, blue arrows show the force of the ground pushing up on the skateboard. These three forces balance out to zero. With no net force, the skateboard doesn't accelerate, but rolls along at a constant speed.
Shock pads are made of polyurethane and rubber. They are very similar to risers but vary in the fact that their sole purpose is to cushion the board from the trucks. Since the trucks are metal and the board wood, whenever the board hits the ground after doing a trick, the energy goes through the truck to the board ─ this has caused boards to crack, split, or even break in half, and shock pads were created to prevent this.