On Sat, 15 Sep 2007 22:00:15 -0700, Hank Wirtz <[email hidden]>
[quote="Quoted message"][quote="Quoted message"]On Sat, 15 Sep 2007 20:21:25 -0700, Hank Wirtz <[email hidden]>
Quoted message said:On Sep 15, 7:17 pm, [email hidden] wrote:
> On Sep 15, 12:08 pm, Lou Holtman <[email hidden]> wrote:
Quoted message said:> > [email hidden] wrote:
> > > On Sep 14, 11:38 pm, "Jeff" <[email hidden]> wrote:
> > >> I have a 12 year old titanium road frame that was custom sized for me by a
> > >> small frame builder and still in decent shape. It has an older steel fork
> > >> that I would like to replace with a carbon one.
Quoted message said:> > > Why???
Quoted message said:> > That is a relevant question.
Quoted message said:> > > Do you _really_ think it will make you faster??
Quoted message said:> > That is a irrelevant question. Why do people have to get faster when
> > they buy something new?
[quote="Quoted message"]> Well, perhaps I misread his intent, but when he explained his riding,
> he said "[I] ride hard and long, but don't do any real racing - but I
> do train with some fairly serious racers who really push me."[/quote]
Quoted message said:> It sure sounds like he wants the fork for speed. If so, it's not
> going to work. If not - why does he want it?
Quoted message said:> - Frank Krygowski
Quoted message said:Might work for climbing speed. A pound off the front end makes a
difference on an 8% grade. At least it did for me.
Dear Hank,
This calculator is set up for convenient comparisons:
http://austinimage.com/bp/velocity/velocity.htmlFor a 150 pound rider putting out a steady 300 watts on the hoods and
a 22 pound bike heading up a 20-mile long 8% grade, the predicted time
drops from 129.901 minutes to 129.264 minutes, or 0.637 minutes, about
38.22 seconds in over two hours.
That's just under a 0.5% speed increase, from 9.238 to 9.283 mph.
The effect is just a little less than a 0.45 mph tailwind blowing you
up the same 8% grade.
Cheers,
Carl Fogel[/quote]
I'm not talking about a 20-mile grade. I'm talking about a half-mile
one. A pound off the front affects the bike's handling, making it FEEL
lighter. And psychologically, that can inspire you to push it harder,
and do that hill in a bigger gear out of the saddle at 12 mph instead
of gearing down and slogging it seated at 8mph. And there's a minute
saved in the span of about three.[/quote]
Dear Hank,
Let's look at the prediction for a half mile 8% grade for a 235 pound
rider (judging by your other post) putting out enough watts to do 12
mph, given a 22 pound bicycle equipped with a 1 pound lighter fork.
Same calculator:
http://austinimage.com/bp/velocity/velocity.htmlIf you managed to do 12 mph up an 8% half-mile grade while still
seated (standing will increase wind drag considerably, but let's be
generous), you'd be putting out 587 watts for 2.49862 minutes.
If you subtract a pound of weight hidden in the front steering tube,
the predicted time will be 2.49057 minutes.
2.49862
-2.49057
-------
0.00805 minutes * 60 seconds / minute = 0.483 seconds out of 150
seconds
Not even half a second faster.
You're claiming that a psychological effect causes you to go from from
8 mph and 377 watts to 12 mph and 587 watts because of an overall
weight change of 1 / 255 pounds, or a 0.4% change in weight leading to
a 58% increase in power output.
As for the lighter handling, it's unlikely that you could tell the
difference while riding, given that the hidden weight is so trivial
and bicycle handling is so inconsequential at 12 mph up 8% grades.
We all have our illusions, so no offense is intended, but this is a
classic example of a 235 pound rider convincing himself that removing
1 pound from his ~20 pound bicycle is going to turn him into Lance
Armstrong zooming up the Alp d'Huez.
That climb averages about 7.7% and is the second Alp d'Huez on this
list of detailed profiles of European climbs:
http://ciclismo.sitiasp.it/motore2.aspx?sid=77dc7b9a7f5946e9896f84344137da9a&lista=true&quanti=20&url=fr&ID=0&pagina=1&filtra=null&da=az&come=af&lingua=eng&commenti=FalseKraig Willet estimated that Armstrong put out around 450 watts for 16
km, with a little bit of flat approach, at 6.38 watts/kg:
http://www.biketechreview.com/performance/la_cant_doit.htmWhatever the hill and your speed are, if you're going faster up the
hill, give yourself the credit, not wishful thinking about removing 16
ounces from the 4,000 or so that you pedal up the hill.
Cheers,
Carl Fogel
