One of my favourite frame-builders, Dave Moulton wrote a couple of good articles on fork rake, trail and handling.

http://davesbikeblog.squarespace.com...f-history.html
http://davesbikeblog.squarespace.com...g-bicycle.html

Rake and trail are integrated with head-angle and wheelbase to determine a bike's handling. There's a strange criss-cross contradiction though. For any given frame & head-angle, as you increase fork-rake, trail decreases and the front-end gets more responsive and twitchier. However, increasing fork-rake also increases wheelbase. So you end up with a bike with a front-end that changes direction easily, but once it's leaned over in a turn, it doesn't want to carve as tight a line as before.

To rectify that oddity with a fork-rake change, I've removed head-tubes and milled the miter in the top & downtubes to increase the head-angle. This reduces the trail and wheelbase for quicker turn-in as well as steady-state cornering. No more Dr. Jekyll & Mr. Hyde handling.