Fork rake, as shown above, is the amount of offset from the steering axis to the dropouts. In combination with head tube angle and wheel size, it determines the amount of geometric trail. A larger trail makes the bike more stable but harder to turn. A smaller trail makes the bike more responsive but "twitchier." Most modern bicycles use a head angle in the 72-74 degree range and a rake of 40-50mm, giving trail of 60-65mm.

http://davesbikeblog.blogspot.com/20...le-bit-of.html