700/23 vs 700/25 tires ?

In article
,
Chalo wrote:

John Forrest Tomlinson wrote:

Chalo wrote:

JFT wrote:

And more to the point, do people trying to go fast care about a little
extra shock absorbtion?

Why wouldn't they? *Every watt of muscle power they spend absorbing
bumps is a watt that doesn't make them go any faster.

http://www.canosoarus.com/08LSRbicycle/LSR%20Bike01.htm
http://davesbikeblog.squarespace.com...ge/Speed04.jpg
http://www.fredrompelberg.com/upload...cord_fiets.JPG

Interesting. *And all the bike racers who do well around the world on
fairly narrow tires are choosing the wrong equipment I suppose?

How would one know whether they were using the optimum size? When was
the last time a pro road racer used 700x28s other than on
cobblestones?

Major Taylor used roughly 1.5" (38mm) tires. and he was racing on
highly groomed 'dromes and board tracks. I reckon he wanted to win
races too.

Tire losses are in flexing the sidewall and flexing the tread.
Thinner side walls dissipate less energy flexing.
Same for tread. But a wider tire cannot have a sidewall as
thin as a narrower tire because of the way the forces work.
Therefore wider tires have thicker casing and dissipate more
energy flexing. The sweet spot for low rolling resistance
is around 21-25 mm width tires.

I see the experiment every day. Rolling along our streets,
stop pedaling and continue to gain on other bicycles with
wide tires.

--
Michael Press

In article ,
wrote:

On Fri, 30 Jan 2009 19:49:09 -0000, "Clive George"
wrote:

"Chalo" wrote in message
...

Thus we'll never really know whether a high quality race tire built
in 28mm or 32mm casing width would be as fast in races as 23mm or 25mm
tires. If anyone demonstrates racing success with an unorthodox tire
size-- whether or not that success is related to the tires-- the
entire population of racers will switch to the novel size.

I really think you're underestimating the effort people go to to work such
things out. There are people out there spending a lot of time with wind
tunnels etc trying to squeeze seconds for races. It's more pertinent for
stuff against the clock (TTs, pursuits, etc), but that's quite strong over
here.

Sure, the superstitious mentality you're describing exists, but at the very
top level it is backed up by actual research.

Dear Clive,

I'm inclined to agree with you . . .

But then I ask myself where the actual research is?

That is, do you have any links to actual research that shows that an
actual rider on a reasonably normal road course is measurably faster
on 20, 23, or 25 mm tires?

I mean actual results for a real rider over an hour or more on a road
surface, to overcome the many complications of road surface versus
smooth drum, wider tire wind drag, frame size affecting aerodynamics,
tire pressure, rider fatigue, and so on.

The more I think about it, the more that I wonder if there are no such
tests. The kinds of differences predicted by isolated theory and
laboratory tests might well be lost in the noise.

Heck, it isn't usually even possible to find out what tire pressures
are actually used in the TDF. And the riders, who tend to stay in the
same pack most days, use a wide variety of tires (often re-badged to
suit their preferences), despite any lab test results indicating which
one has the best theoretical rolling resistance.

Come to think of it, is there a lot of research that shows that 700c
tires, front and rear, are the very best height for speed on
traditional road bicycles?

Well, there was a brief trend of using 650c wheels (and also "funny
bikes" with mismatched-size wheels). The theory that the smaller wheels
meant a lower frontal area didn't work out in the wind tunnel, and funny
bikes were banned (UCI rules say the wheels have to be the same size).

Today, all pros (and, I think, all pro Triathletes) use 700c wheels for
road and TTing, excepting only a few very short riders who might be
using 650c.

--
Ryan Cousineau http://www.wiredcola.com/
"In other newsgroups, they killfile trolls."
"In rec.bicycles.racing, we coach them."

Michael Press wrote:

Tire losses are in flexing the sidewall and flexing the tread.
Thinner side walls dissipate less energy flexing.
Same for tread. But a wider tire cannot have a sidewall as
thin as a narrower tire because of the way the forces work.
Therefore wider tires have thicker casing and dissipate more
energy flexing.

Don't think so. Fatter tires have to distort much less to establish a
given contact patch. Even if there is less rubber being worked in a
narrow tire, it is being worked to a much higher degree of
deflection. This accounts for the roller tests Jobst Brandt has
posted many times which show that wider tires of equal construction
exhibit lower rolling resistance than narrower ones.

The sweet spot for low rolling resistance
is around 21-25 mm width tires.

That's entirely dependent upon load and surface quality. Just like a
suspended vehicle can maintain a higher speed than an unsuspended
vehicle past a certain function of surface roughness and speed, a
wider, softer tire can be faster when surface quality is taken into
account. Were that not the case, MTB racers could use 1.5" tires or
even road bike tires. But in fact they would not be competitive if
they did so.

I see the experiment every day. Rolling along our streets,
stop pedaling and continue to gain on other bicycles with
wide tires.

I do that on 700x60 tires, merely on the basis of my superior
mass:frontal area ratio and the fact that my bike is in good running
condition. It's the same whether I'm running 700x32 Paselas or 700x60
Big Apples.

Chalo

On Fri, 30 Jan 2009 11:29:55 -0700, wrote:

On Fri, 30 Jan 2009 12:18:01 GMT, John Forrest Tomlinson
wrote:

On Thu, 29 Jan 2009 21:36:31 -0700, wrote:

It's a tricky situation to model.

There's always a vertical component.

Dear Carl,

I was surpised that someone as good as physics left it out earlier but
I assume you did that to simplify the subject for simple people like
me.

Thank you.

Dear John,

As usual, it was only left out in your imagination.

Dear er,

I guess I am missing it in the text below, which you wrote:

More rim protection is needed at higher speeds because impact roughly
corresponds to kinetic energy, which is half the mass times the square
of the velocity--it rises even faster than the speed.

At 20 mph, a rider hits a chunk of gravel (oops!) with an impact of
20^2 whomps, or 400 whomps.

At 25 mph, the same rider hits the same chunk of gravel at 25^2
whomps, or 625 whomps.

At 30 mph, he hits it at 30^2 whomps, or 900 whomps, more than twice
as hard.

That's why drivers slow down on rough roads and why faster riders get
more pinch flats on bicycles.

On Fri, 30 Jan 2009 21:00:53 GMT, Ryan Cousineau
wrote:

In the era of 19mm tires, it was an experiment that was down to a lack
of evidence. I don't know how fast the trickle of information was, but
it appears at some point tires evolved back to the 23mm range of today.
As much as anything, that may speak to the subtlety of the advantages.

Yes - excellent point..

On Fri, 30 Jan 2009 14:28:19 -0700, wrote:

On Fri, 30 Jan 2009 19:49:09 -0000, "Clive George"
wrote:

"Chalo" wrote in message
...

Thus we'll never really know whether a high quality race tire built
in 28mm or 32mm casing width would be as fast in races as 23mm or 25mm
tires. If anyone demonstrates racing success with an unorthodox tire
size-- whether or not that success is related to the tires-- the
entire population of racers will switch to the novel size.

I really think you're underestimating the effort people go to to work such
things out. There are people out there spending a lot of time with wind
tunnels etc trying to squeeze seconds for races. It's more pertinent for
stuff against the clock (TTs, pursuits, etc), but that's quite strong over
here.

Sure, the superstitious mentality you're describing exists, but at the very
top level it is backed up by actual research.

Dear Clive,

I'm inclined to agree with you . . .

But then I ask myself where the actual research is?

That is, do you have any links to actual research that shows that an
actual rider on a reasonably normal road course is measurably faster
on 20, 23, or 25 mm tires?

I mean actual results for a real rider over an hour or more on a road
surface, to overcome the many complications of road surface versus
smooth drum, wider tire wind drag, frame size affecting aerodynamics,
tire pressure, rider fatigue, and so on.

The more I think about it, the more that I wonder if there are no such
tests. The kinds of differences predicted by isolated theory and
laboratory tests might well be lost in the noise.

If the tests don't exist or can't exist, then you should be looking at
practice by the people who succeed in the endeavour, rather than the
ideas of some slow guy who like to use examples from the 1920 to talk
about racing equipment, or some huge guy who weighs more than twice
what a lot of good bike racers do.

On Fri, 30 Jan 2009 07:04:38 -0800 (PST), "
wrote:

On Jan 30, 6:39*am, John Forrest Tomlinson
wrote:
On Fri, 30 Jan 2009 00:46:50 -0700, wrote:
Unfortunately, citing racers' equipment is a double-edged sword.

All too often, we have no real evidence whether they won because or in
spite of their equipment.

Yes, so far better to rely on the clear thinking ideas of a person who
as far as we know has zero practical experience in bike racing as a
rider, coach, mechanic, or any other capacity such as Carl Fogel.

And how many of the bikes or equipment used by Armstrong was designed
by a professional bike racer or director? None. It was designed by
engineers who likely know how to ride a bike assigned to the job by
Trek or some other company. Having specific experience is
unnecessary. How many Nascar cars or Goodyear tires are designed by
people who have driven at 200 mph on 45 degree banked tracks? None.
Where do you get this idea that a person needs specific experience to
make something? Oppenheimer was not a pilot or soldier so he should
not have been able or qualified to make an atomic bomb.

They have practical experience of working in the milieu. They do not
leave grad school having studied airplane wind design and make
recommendation that are valid in bikes from the start. Rather they
work with the competitors, looking at the actual situations and
practices and seeing how they can be improved.

That is practical experience.

Carl Fogel and some engineers in this group do not understand the
demands or issues in bike racing, and w/o understanding the issues
facing the product being studied, even a good engineer will often be
off-base.

On Fri, 30 Jan 2009 11:31:22 -0700, wrote:


Dear John,

Ah, your usual signal that you have no argument!

Dear Carl,

As usual you are a coward who refuses to answer relevant questions
about himself.

On Fri, 30 Jan 2009 21:06:56 GMT, Ryan Cousineau
wrote:

I've raced. I've driven mechanical support vehicles in races. As a
neutral support vehicle mechanic, I've changed a wheel for a racer
(badly). I've won races, albeit pointless amateur low-cat ones. I've
done all the mechanical work on all my racing bicycles. I've ridden
road, crits, TTs, track (not in competition yet), cyclocross, mountain
bikes, and if it wasn't for the narrow-mindedness of the local racing
association, would have raced cyclocross on a tandem. I've built up a
Giant TCR 0 from a frame and a bunch of boxes of Dura-Ace parts. Are my
bona fides sufficient?

I agree with Carl's claim that "all too often, we have no real evidence
whether [racers] won because or in spite of their equipment."

Any questions?

Yes -- one:

So who do you think is more likely to be right about tire choice for
racing: you who've used tires in races, looked closely at other tires
that successful racers use, or Carl?

In article ,
John Forrest Tomlinson wrote:

On Fri, 30 Jan 2009 21:06:56 GMT, Ryan Cousineau
wrote:

I've raced. I've driven mechanical support vehicles in races. As a
neutral support vehicle mechanic, I've changed a wheel for a racer
(badly). I've won races, albeit pointless amateur low-cat ones. I've
done all the mechanical work on all my racing bicycles. I've ridden
road, crits, TTs, track (not in competition yet), cyclocross, mountain
bikes, and if it wasn't for the narrow-mindedness of the local racing
association, would have raced cyclocross on a tandem. I've built up a
Giant TCR 0 from a frame and a bunch of boxes of Dura-Ace parts. Are my
bona fides sufficient?

I agree with Carl's claim that "all too often, we have no real evidence
whether [racers] won because or in spite of their equipment."

Any questions?

Yes -- one:

So who do you think is more likely to be right about tire choice for
racing: you who've used tires in races, looked closely at other tires
that successful racers use, or Carl?

Carl, in my opinion, has thought about this question as carefully as
most bike racers. He has thought about it at least as carefully as I
have. I would say that my opinions about tire choices in races are first
informed by price (no seriously, I get a really good local deal on Kenda
Kaliente 23mm clinchers, so I use those), and the opinion I give to
those who ask me is to not worry much about tires, and probably to run
at least a 23.

So Carl's advice is as good as mine.

More to the point, Carl is right: there's a lot of equipment choices in
bike racing that are either hard to analyze, or hard to defend.

Don't get me started on cellar tire aging, and yet that's something the
Discovery/Postal mechanics were very keen on. It probably didn't hurt or
help,

--
Ryan Cousineau http://www.wiredcola.com/
"In other newsgroups, they killfile trolls."
"In rec.bicycles.racing, we coach them."