In support of 'Sport' road bicycles

We like riding 'Sport' style road bicycles when we aren't racing. They are more comfortable, less twitchy, and are more tolerant of less than perfect paved surfaces. By our definition a sport bicycle has 44 or 45 cm chainstays, a headstay angle of about 73 degrees, and a bottom bracket drop between 7 and 8 centimeters. This geomoetry was more common in years past. Not many framesets with this geometry are currently being produced.

Here's why we think we prefer Sport geometry:

  • Straight line stability instead of fast steering response
  • Mid corner confidence .Longer chainstays are more tolerant of chainline imperfections and crosschaining.
  • Smoother ride provided by longer chainstays and shallower fork angle. (see below)

We beleive, but cannot prove, that longer chainstays and shallower fork angles both contribute to a smoother ride. Our theory revolves around where the rear axle is in relation to where the rider meets the saddle. If the axle is well behind the saddle then the following might be happening.

  1. The rear wheel rolls over a bump.
  2. The rear axle pushes up on the frame.
  3. The rider is relatively heavy compared to the biycle and is resistant to being pushed up. The saddle acts as the pivot point. The rear axle applies pressure up, the frame pivots under the saddle, and the front of the frame applies downward pressure against the fork.
  4. The shallow fork angle allows for/aft fork flex to have a smaller but significant up/down component. This vertical component allows the front of the frame to go down.

The next effect is that the for/aft flex in the fork (if the angle is not steep) allows the frame to pivot under the saddle and provide a type of suspension instead of simply pushing the saddle (and rider) up.

Finding a modern 'Sport' road bicycle is maybe a larger challange that explaining why we like them. Lots of 70's framesets fit the bill. A few from the 1980's do as well. But the trend back then was to build the better quality bikes more like road race bicycles with shorter chainstays and tighter fork angles. At the time of this writing 'The Editor' is riding a Soma ES frameset that almost measures in. Slim is still working on the Trek 610. On the days his Trek is roadworthy it is a fine example of what a 'Sport' road bicycle can be.