[robo]

You're missing the bit that Sierra's upright has negative trail, and offset mushrooms set it to zero, making the wheel axle intersect the kingping axis.
Quote.

Alga has already pointed out that the mushrooms set the trail to zero<which i was told gave a positive trail> so where do the sierra upright boys go now. More caster.?????? We have what the donor of our choice gave us and the only practical way to rectify the problem is to frig the top wishbone or pivot points. Any other method would involve purpose made uprights which no one is going to do.

Bob