Ok, after wheel bite, the next most important issue for trucks is stability. If you've ever ridden a skateboard and thought that it turned funny or felt squirrely like it was going all over the place, it was probably because of badly built trucks.

It doesn't take a rocket scientist to understand that to make something more stable, move it's center of gravity lower to the ground. Sports cars and race cars are built this way so they can go around turns quickly without skidding out or tipping over. So how does this apply to skateboards? It's simple: the lower the ring of the hanger is to the ground, the more stable the truck is. This is where a lot of truck manufacturers make mistakes. They spend tons of effort using statics to carefully calculate the forces on a truck when it pivots, but unless they expect you to skate standing still, it's the wrong way to design a truck. The forces on a skate truck are wildly different when you add motion to the equation (dynamics, not statics), and these are the forces that determine the truck's stability.

LO Trucks with Riser Pads versus HI Trucks

It's obvious that LO trucks are more stable than HI trucks. But what if you need higher trucks because you skate larger wheels? The best thing to do if you ride big wheels is to buy LO trucks and add some riser pads to make them higher. Your skateboard will turn better and it'll be far more stable than if you used HI trucks. That may seem strange, but it's the truth. The reason is actually quite simple. The center of the ring in the hanger is a pivot point of the truck (between the bushings, click on the Turning link below for details). The closer this point is to the axle (so closer to the ground), the lower the center of gravity and the more stable the ride. So, if you were cruising down the street on some HI trucks, which have the ring far away from the axle and the ground, and threw your weight into a turn, the skateboard would have the tendancy to tip forward on the leading wheels and you could slide out. LO trucks with risers puts force of the turn closer to the center of the axle, balancing the force more evenly between all 4 wheels. Alpha trucks are designed this way, with the ring as low to the ground as possible, giving you a very stable ride.

Ok, you're not always moving very fast on a skateboard, say if you're learning a new trick. In that case you want your skateboard to be very stable when you're practically standing still. Alpha trucks come with ultra-high rebound urethane bushings that provide all the stabilization you need at very slow speeds. So whether you skate slow or fast, Alpha trucks give you all the stability you need to skate your best.


Kingpin Clearance

Another important issue with trucks is the kingpin clearance. If your kingpin is too low and sticks out below the hanger, it'll catch when you grind. But having too much clearance is bad too. Truck manufacturers that brag their trucks have tons of kingpin clearance aren't seeing the big picture. They make a big kingpin clearance by moving the axle away from the ring of the hanger. If they don't reduce the height of the baseplate to compensate for the height added to the hanger, they end up with a HI truck (and we already know those are less stable). If they do reduce the height of the baseplate, they end up shrinking the action angle and making the turning radius worse. The bottom line is to beware of trucks with a ton of kingpin clearance because they probably won't ride very smoothly. Alpha trucks are designed with just the right amount of kingpin clearance: enough for grinding, but not too much to make the truck unstable.