Back in the day when i was starting to build I tried to absorb all i could WRT steering geometry. I went through dozens of frame spec charts from manufactures (now I know that these were not fully what the actual bikes used...) calculating the trails. Discovered Castor Angle (Eisentraut and Bill Boston), measured as many frames for lift or drop during steering angle changes. I remember the English publication that had a column on mechanical things (Mullet's Mechanics, or something like that) that had math formulas to derive the head angle, wheel size, rake combo that produced the "right" amount of lift/drop needed for a handling goal. 81* castor angles, Wheel Flop Factors, over/under steer all are just different ways of looking at the same thing, choose your language right and others will follow you like a Pied Piper.

After a few years I kind of gave up trying to be a student of steering spec. I found that the range of dimensions were narrow when other frame design needs were taken into acount (like front center/toe overlap or available tire/wheel sizes). I also found that how you loaded the bike (I was into loaded touring at the time) had far more import to handling then a CM of trail difference. Lastly i decided that i liked a certain feel to the handling and for my bikes centered my steering geometrys there.

It seems that so much of this discussion is cyclic (intended pun) with a new generation of builders that weren't around BITD. Only now there's the interweb to be able to draw many others into your thinkings. The best example of this in Jan Heine's Bicycle Quartery, and his attempts to understand bike handling WRT trail and tire size.

After so many thousands of builders/designers that came before us and have explored the varying dimensions and specs that can be produced and ridden that the vast majority of bikes have so little difference should say something. I have no problem reading one more discussion on steering geometry, even to add my views, but I don't expect to really have any "ah ha" moments.

Having said all that i tend to build with around 6cm of trail and choose the head angle with reference to the front center as much as the handling response. I don't carry much weight on the front of the bike (when loaded for touring there's a lot more rear weight the front). I feel that there's FAR more tire profile/air pressure controled road surface damping going on then fork blade flex, certainly for the high frequency buzz. Andy.