Originally Posted by
Kontact
I'm not understanding your post. Trail is the product of rake and HTA. Regardless of HTA, if you use a rake that produces a certain trail, the bike will handle similarly in terms of what trail does.
23mm tires:
72.5° HTA + 48mm rake = 56mm trail
73.5° HTA + 42mm rake = 56mm trail
Both bikes will have very similar low and high speed handling because they have the same trail. Rake is the tool used to produce a particular trail given the need to vary HTA to produce different reach and wheelbases.
You are right about the math and probably about neutral trail bikes. I like less trail and I find that optimum trail varies with HTA. (Optimuim being the handling I like. Since I only spec forks and frames to be ridden my me, that is all that matters to me. I have ridden bikes from less than 72 to 75 HTA. The bikes with really sweet handling (in my book, I don't care about anybody else's) all fall on a diagonal line on a HTA-rake plot. The corresponding trails I believe also follow a line. I haven't plotted them; it may be a curve. It is not a constant trail.
Ben