Jan: I haven't read the charts and statistical results.
When the test were done, did you keep tires the same pressure?
Or, did you try to compensate for compression factor?
Was materiel factored, silk, cotton, polyester.nylon, kevlar difference in
protector strip composition.
How about rim weight and flexibility?
Just a few things that wrinkle my brow.
>From a practical point, most racers prefer tubulars because of the safety in
riding, cornering control, shock absorbtion, etc.
As to the "Q"/tread factor, how come no one has mentioned core flexibility,
sit bone width and depth, upper thigh and butt muscle mass, crotch/pelvis
width,?
Anybody considered the directional down force efficiency angle between lower
leg and ankle, plus knee into top bar direction for power and pedal motion.
Anybody ever watch the front views of the racers in the various tours?
Those knees look almost touching the top tubes.
Doesn't anybody wonder why and try to factor that in when thinking about
saddle shape and position while pontificating about The P's and "Q"s of all
this?
Methinks we need a little more fact than speculation if you get my drift.
Curious minds want to know.
Ted Ernst
Palos Verdes Estates
CA USA
> At 4:24 PM -0800 11/4/08, Isaac Schell wrote:
>>What do you use to test a tires speed? Is this a machine test or a human
>>test? Why do pro's ride sewups if their slower? Am I misunderstanding this
>>test or are you really busting a long time cycling myth?
>
> It's not Bicycle Quarterly who busted this myth. Tests on steel drums have
> shown for a long time that tubular tires are slower than clinchers. In
> fact, they predicted that they were much slower. If we busted a myth, it's
> that tubulars are way slower. We found that they are a bit slower...
>
> Our test was a rolldown test on a real road with a real rider. We used a
> carefully selected hill - very steep at first to get up to speed quickly,
> then decreasing gradient, so that the speed remains largely constant.
> During this "runout" we had a timed section. The speeds were moderate -
> too fast, and you are testing aerodynamics, rather than rolling
> resistance.
>
> The advantage of this test is that it uses real-life conditions. In fact,
> the rider is crucial, because much of the energy of vibration appears to
> be absorbed in the rider. So a riderless bike will not be a good model for
> real-life conditions. A steel drum is worse, because it does not consider
> the ability of the tires to absorb vibrations. A bike that floats over
> surface irregularities is faster than one that vibrates a lot.
>
> The disadvantage our test is that you need to control the conditions very
> carefully. Temperature and wind both affect the speed of our rider. (Tires
> roll much faster when they are hot.) Changes in position would be
> terrible. We carefully selected the day when we tested, and we tested the
> same tires several times to make sure we had repeatable results. Also,
> each tire/pressure combination was repeated at least three times. When we
> went to the wind tunnel for another test, we found that replicating the
> same position on the hoods was no problem.
>
> Some have asserted that it would be impossible to control the extraneous
> variables, especially wind, and that our results therefore were of little
> use.
>
> To evaluate this concern, we did a statistical analysis of all our
> results. A statistical analysis shows whether the results are just random
> chance, or whether they actually show differences between tires. For
> example, if you flip a coin and you get tails 5 times in a row, that can
> be chance. If you get tails 50 times in a row, you are likely to have a
> fake coin with tails on both sides.
>
> For our test, you want the scatter among repeats of the same configuration
> to be much smaller than the differences between tires. Fortunately, my
> co-author has a Ph.D. with a minor in statistics - see
>
> http://www.vintagebicyclepress.com/
>
> The statistical analysis found that there was a less than 1 in 10,000
> chance that we were just seeing random coincidences. So we are quite
> confident that our results are good. We could not detect small differences
> between similar tires (such as between the Deda 24 mm clincher and the
> Clement 28 mm tubular) - the follow-up article in BQ Vol. 5, No. 3
> includes a chart that shows which tires are different, and which are too
> close to tell.
>
> Anyhow, that is how we did our real-road tests of tires. Among many
> interesting results, we found that different tires resulted in 20% speed
> differences, between fastest and slowest. However, among modern racing
> tires, the speed differences were smaller, but still significant. Wider
> touring tires showed the biggest differences. Grand Bois' tires scored in
> the middle of the pack. The maker then used our results to redesign their
> tires, and when we tested the newer models, they were among the faster
> tires. Only the handmade Dedas and the Clement del Mundos were
> significantly faster.
>
> The original article in Bicycle Quarterly Vol. 5, No. 1 was eight pages
> long, and there have been some follow-ups, so this can only be a very
> brief summary - especially since it is only marginally on-topic.
>
> Disclosure: Vintage Bicycle Press sells Grand Bois tires.
>
> Jan Heine
> Editor
> Bicycle Quarterly
> 140 Lakeside Ave #C
> Seattle WA 98122
> http://www.bikequarterly.com
> --