on 7/1/04 9:20 AM, Steve Kurt at kurtsj@mtco.com wrote:
> I gotta agree with Todd here, except for the part about testing being
> expensive and difficult. In this particular case, the goal would be to
> measure the spring constant of the rear end of the frame. It would be
> possible to just apply a load to the frame (i.e. put 100 pounds on the
> saddle), and measure the change in distance from the seatlug to the rear
> axle. Or, measure the change in vertical height of the seatlug and the
> rear axle; measure these in the loaded and unloaded state, and use the
> changes to calculate the compliance of the frame.
This is only step one in the required testing. Step two is to determine if the amount of deflection provided by such stays (actually, the difference between the deflection with straight stays and deflection with curved stays) is large enough to be noticeable. So, if the amount of deflection is less than 1% of the deflection of tires, saddle, seatpost, stem, handlebars, etc. then it's not significant.
For example, Specialized has svibrationshown that the "Zertz" insert in their seatpost reduces the transmission of vibrations at certain frequencies to the saddle. However, they have not yet shown that this reduction provides any *noticeable* benefit to the rider. A double blind test could be used to determine this. I've mentioned this to them, and so far they haven't shown much interest in pursuing it.
Todd Kuzma
Heron Bicycles
Tullio's Big Dog Cyclery
LaSalle, IL 815-223-1776
http://www.heronbicycles.com
http://www.tullios.com