Inward tilt is negative, outward tilt is positive. Camber is used to distribute load across the entire tread. Improper camber makes the tire wear on one edge, and causes the vehicle to pull to the side that has the most positive camber. If the distance is closer at the front, it's called toe-in. If the difference is closer at the rear, it's called toe-out.
Some suppliers suggest that they have reinvented the wheel.
Actually, there have been no light truck spring design breakthroughs in quite some time. Rate, in the simplest sense, is a measurement of the load required to compress the spring a given distance. In other words, it is a gauge of spring strength and flexibility. Rate is influenced by several factors including material grade and thickness, leaf length, leaf end configuration and interleaf friction. Developing a good functional design involves closely evaluating the vehicle's on and off-road handling, ride, and body roll characteristics, then using this data to design a product matched to the vehicle.