Originally Posted by
KKBHH
Well, since the entire lightweight bicycle doesn't weigh very much then why not suspend the rider on the frame instead of suspending the rider and frame on the wheels ? In the first case the entire bicycle would be un-sprung weight while in the second case only the wheels and suspension would be un-sprung weight. But again the bicycle doesn't weigh very much against the total weight of bicycle and rider.
The problems would seem to be that a seat suspension would hinder pedaling while sitting in the seat. But then if there were only a handlebar suspension that would tend to pitch the rider's weight forward. If there were both a seat suspension and a handlebar suspension the rider would move more vertically.
Now one bicycle developer has a seat compliance system that moves the seat mostly front and rear and not as much up and down. I suppose that the development has our attention.
My solution is a stiff frame with a deflecting fork and deflecting seat post. Of course my sport is not long-range rides but short downhill courses like a paved sports-car track but relative to the 40 MPH speed of the bicycle.
Now we all know that a wheel suspension at the rear of a bicycle does reduce pedaling effectiveness.
The Specialized Roubaix has a handlebar suspension on top of the headset allowing 20 mm of vertical travel. The latest version of it is sprung and damped. The original didn’t have the damper. They did apparently test a similar system on the seat post but found that riders didn’t like the way it pedalled with vertical compliance (not surprisingly). So they went with a more typical compliant seat post to provide a bit of comfort. Most modern bikes now have fairly flexible seat posts to add comfort. The D-shaped carbon post on my Defy is notably springy, but because it only defects backward it doesn’t affect pedalling.