I'm getting weird wear on my front tire. The leading edge of each tread (part of tread that touches pavement first) gets very little wear. The trailing edge is nearly worn down to the tire and I only have 4K miles on my Ruckus. A friend told me this is common on motorcycles and is related to preload. I seem to recall spring adjustments on other motorcycles I've had, but this Ruckus doesn't seem to have any way to deal with preload. All my service manual mentions is the spring tolerances in the forks.
Is there a way to adjust preload and if so how should it be done?