Motorcycle fork bottom which is stiffer front-to-back than side-to-side

Abstract

A motorcycle or bicycle suspension having adjustable side-to-side flexibility. The suspension includes a telescopic fork and a fork bottom which couples the fork to the axle of a wheel. The fork bottom and the fork are stiff in the direction of travel, to avoid flexing under heavy braking. The fork bottom is flexible in the lateral direction, to improve the ability of the tire to stay in contact with the ground when leaned over and cornering over irregular, bumpy ground. The lateral flexibility of the fork bottom is adjustable by tightening or loosening a tension cable which is attached to the ends of the fork bottom and stretched over a fulcrum in the middle of the fork bottom. Tightening the tension cable increases sideways thrust of the fulcrum against the fork bottom, reducing the lateral flexibility of the fork bottom.

1 . A motorcycle comprising: 
 (a) a frame having a steering tube;    (b) an engine coupled to the frame;    (c) a front axle;    (d) a front wheel rotatably coupled to the front axle; and    (e) a front suspension including, 
 (1) a pair of telescopic forks, each having, 
 (i) an upper fork tube,  
 (ii) a lower fork tube slidably coupled to the upper fork tube, wherein one of the upper fork tube and the inner fork tube is disposed partially within the other, and  
 (iii) a fork bottom rigidly coupling the front axle to the lower fork tube, the fork bottom having greater stiffness in a longitudinal direction of travel of the motorcycle than in a lateral direction generally parallel to the front axle, and  
 
 (2) an upper triple clamp and a lower triple clamp coupled to the upper fork tubes and rotatably coupled to the steering tube.  
   
   
   
       2 . The motorcycle of  claim 1  wherein the front suspension further includes: 
 (3) a fork buttress rigidly coupled to the lower fork tubes of the pair of telescopic forks.    
   
   
       3 . The motorcycle of  claim 1  wherein the front suspension further includes: 
 (3) a fork buttress rigidly coupled to the fork bottoms of the pair of telescopic forks.    
   
   
       4 . The motorcycle of  claim 3  wherein: 
 the fork buttress is rigidly coupled between the lower fork tube and the fork bottom of each of the pair of telescopic forks.    
   
   
       5 . The motorcycle of  claim 1  wherein the fork bottom of each telescopic fork comprises: 
 a body having a substantially continuous outer wall having a first dimension in the longitudinal direction, and front and rear end walls having a second dimension substantially perpendicular to the longitudinal direction and less than half the first dimension;    whereby a cross-sectional shape of the body provides the greater stiffness in the longitudinal direction of travel of the motorcycle than in the lateral direction generally parallel to the front axle.    
   
   
       6 . An improvement in a motorcycle having a frame, an engine coupled to the frame, and a front wheel axle coupled to the frame by a pair of telescopic forks, wherein the improvement comprises: 
 means for coupling the front wheel axle to the telescopic forks;    wherein the means for coupling has far greater resistance (i) to flex in response to forces applied front-to-rear substantially parallel to a direction of travel of the motorcycle in accordance with braking, than (ii) to flex in response to side-to-side lateral forces substantially perpendicular to the direction of travel in accordance with road surface variations.    
   
   
       7 . The improvement of  claim 6  in the motorcycle, wherein the improvement further comprises: 
 the means for coupling comprising a pair of fork bottoms each coupling a respective telescopic fork to the front wheel axle; and    a fork buttress coupling the pair of fork bottoms to each other.