on 12/23/03 11:31 PM, NortonMarg@aol.com at NortonMarg@aol.com wrote:
> If you built a straight bladed fork out of the
> exact same (pencil) tubing, you would get LESS deflection at the tip because
> you
> wouldn't have the angle allowing as much movement.
> I saw one old Raleigh fork that must have had 4" of rake with all the bend in
> the bottom third or fourth of the blade. With the wheel pushing straight up
> on that, it has a lot of leverage to move the fork blade in the direction of
> what amounts to "suspension travel".
There is a common thread on rec.bicycles.tech about straight versus curved forks. The bottom line is that they ride the same. On a straight fork, the offset is accomplished at the crown. The curve in the blade makes no difference in ride quality as most of the fork flex occurs at the crown and in the steerer.
Your example above about the Raleigh fork illustrates this. You state "with the wheel pushing straight up on that . . ." However, the fork does not flex upward over bumps. It flexes rearward. The fork is cantilevered off of the frame and its pivot point is the crown. The steerer must bow in the opposite direction (forward) to permit the movement at the crown.
I believe that the amount of curve shown on the fork blades on both older and current bikes reflects the fashion and prevailing myths of the day. I've heard theories that older forks were made more flexible to deal with the rough roads, and I have heard theories that older forks were made stiffer to deal with rough roads (so they would not fail under the abuse).
E-Richie wrote in the 1993 Bridgestone catalog that the Cinelli fully-sloping crown was designed to reduce the length of the fork blade. This would, in turn, strengthen the fork in response to poor road conditions (and poor torchwork) of the day.
Todd Kuzma
Heron Bicycles
Tullio's Big Dog Cyclery
LaSalle, IL 815-223-1776
http://www.heronbicycles.com
http://www.tullios.com