Many skaters say that if you're not falling, you're not skating hard enough. There may be some truth to that, unless you're falling because your equipment sucks. Usually the blame lays squarely on your trucks. You're cruising along, throw your weight into a sharp carve, and bam, your wheels bite against the bottom of your deck and you go flying. Or you catch a nice kickflip, but you fall because you get wheel bite when you land.
Wheel bite has plagued skateboarders for decades. In the old days there used to be little cut-outs in the deck above the wheels. They were ok when boards were 10" wide, but as boards got skinnier and tricks got gnarlier, the cut-outs became a weak point on the deck and had to go. You can still see these cut-outs on longboard decks, but they really don't work all that well at preventing wheel bite.
Another attempt manufacturers devised to prevent wheel bite, and sadly still use today, is to make a HI truck--a taller verion of their MID or LO trucks. They increase the height of the truck by moving the axle further away from the baseplate. Unfortunately, this creates an unstable truck and a pretty crappy ride (click on the Stability link below to learn about why you should avoid most HI trucks and use riser pads instead).
Before Alpha came along, the only way to prevent wheel bite was to crank down on your bushings to make your trucks as tight as possible. But tight trucks equal no turning, and who the hell wants a skateboard that doesn't turn? Really, the only way to prevent wheel bite is to design a truck with wheel bite 'stops' that literally stop the hanger from pivoting just before the wheels hit the bottom of the deck. It's a simple concept, but very difficult to do: how do you make the wheel bite stops adjustable for different wheel sizes; how do you make them strong yet lightweight; how about small and not in the way? It's no trivial task. It took us a few years and countless prototypes before we figured it out.
Alpha trucks have a pair of tiny set screws in the ring portion of the hanger on either side of the kingpin. Instead of the wheels biting the deck when the hanger pivots too far, the set screws (shown in yellow in the middle cross-section picture below) bind against the kingpin and stop the hanger before the wheels bite. The best part of our trucks is that you can skate them as loose as you want without getting wheel bite! The set screws also stabilize the hanger on the kingpin and eliminate what's called 'hanger jiggle.' When other trucks are loose, the hanger has the tendancy to jiggle between the bushings and can give you a pretty squirrely ride. With the set screws right next to the kingpin in our trucks, hanger jiggle is no longer an issue.
You adjust the set screws based on the size of your wheels. The closer the set screws are to the kingpin, the less pivoting is needed for the set screws to bind. So for big wheels, tighten the set screws, and for small wheels, loosen the set screws. The set screws lock in place, so once you adjust them, you don't have to worry about them again. It's really that simple!