wheel aerodynamic advantage

wrote:

If there were any easy way to add enough speed to be felt, every
bicycle would have it.

Speed isn't easy to feel. Acceleration is.

wrote:
I guess that I'll save my money. I've always suspected that there
wouldn't be that much difference, but when you talk to other people,
they claim that they notice a tremendous advantage. The power of
advertisement is incredible.

It is truly amazing... but people like to get new stuff and it helps
if they can make up a reason to justify it.

I decided to focus on TTs this year, and put together a bike specially
for it. TT frame, aerobars, disk cover, 82mm front wheel, skinsuit,
aero helmet. Previously I used 30mm rims with aero spokes, and clip on
bars on my regular road bike... nothing else special. I gained a
little over 3% in speed, or 0.8 mph. Oddly, this is exactly what I
predicted based on available test data. Was it worth it? I'm glad I
did it, but I'm still well out the prize money and the glory...

On Mon, 17 Nov 2008 21:55:49 -0800, Robert Chung wrote:

wrote:

If there were any easy way to add enough speed to be felt, every
bicycle would have it.

Speed isn't easy to feel. Acceleration is.

heretic.

On Nov 17, 11:53 pm, wrote:
On Mon, 17 Nov 2008 14:19:29 -0800 (PST), "



wrote:
On Nov 17, 12:36 pm, wrote:
On Sun, 16 Nov 2008 23:44:25 -0800 (PST), "

wrote:
On Nov 16, 6:30 pm, wrote:
On Sun, 16 Nov 2008 13:37:58 -0800 (PST), Chalo

wrote:
Carl Fogel wrote:

Andres Muro wrote:

If I got a wheels with 28 to 30 mm rims and 16 to 24 aero spokes,
will I feel a difference at speeds over 20mph?

Any advantages in speed over the more conventional 24mm wheels?

This page lets you try various wheels on various courses:
http://www.analyticcycling.com/DiffE...urse_Page.html

4,000 meter standing-start course

seconds for 4km standing-start generic TT course
-------
461.80 standard 32-spoke box wheels
452.11 lowest drag C(obb data) wheels (Deep S90)

That's about 2% faster, roughly an average of 19.8 mph versus 19.4
mph. The difference can be seen on a cyclocomputer, but probably not
felt by the rider.

Funny. Almost all my wheels have 48 round spokes, and I ride so
slowly I sometimes wonder whether I'm moving backwards. I had always
credited the foolishly unaerodynamic wheels for my laughable
performance. I reckoned if I only had enough money to buy some swell
wheels with NACA airfoil rims and 7 bladed spokes in a three-quarters
radial pattern, I'd be even faster than those Euro pros who are
handicapped by Luddite UCI rules.

Now you're telling me all I have to gain is two lousy percent?!
That's just not going to work. I need a second opinion.

Chalo

Dear Chalo,

Okay, here's a second opinion: red paint.

Cheers,

Carl Fogel

[snip]

But, Carl, your advice wasn't dynamic, didn't anticipate Andres'
improvement. The stronger and more fit he becomes, the faster he goes,
and the greater the aerodynamic advantage of the expenditure.

[snip]

Dear Harry,

Actually, anticipating significant improvement for a rider as
experienced as Andres is A) unlikely and B) not going to make much
difference anyway.

At 250 watts and ~20 mph average speed from a standing start for 4 km,
the wheels save about ten seconds in about seven or eight minutes.

At 400 watts and ~25 mph average speed from a standing start for 4 km,
they save about twelve seconds in about six minutes.

http://www.analyticcycling.com/DiffE...urse_Page.html

4,000 meter standing-start course

seconds for 4km standing-start generic TT course 250 watts
-------
461.80 standard 32-spoke box wheels
452.11 lowest drag C(obb data) wheels (Deep S90)
------
9.69 / 461.80 = 2.1% faster time

seconds for 4km standing-start generic TT course 400 watts
-------
368.63 standard 32-spoke box wheels
356.36 lowest drag C(obb data) wheels (Deep S90)
------
12.27 / 368.63 = 3.3% faster time

Cheers,

Carl Fogel

I guess that I'll save my money. I've always suspected that there
wouldn't be that much difference, but when you talk to other people,
they claim that they notice a tremendous advantage. The power of
advertisement is incredible.

I wish I would be so easily influenced by ads. I guess, the joy that
people get is tremendous when they spend money and feel a great
improvement. I'm always too cynical to notice improvement anyways.

Dear Andres,

I sympathize.

The speed differences debated on RBT often turn out to be much smaller
than what ~20 mph riders like you and me hope for.

If there were any easy way to add enough speed to be felt, every
bicycle would have it.

Cheers,

Carl Fogel

Jan Heine, editor and publisher of Bicycle Quarterly has been testing
tires for speed. He is a strong masters randonneur, who I suspect
maintains 20mph on centuries.

He has this comment on our perceptions of speed I haven't seen before.

"The biggest problem is that what feels fast and what is fast are two
different things with tires. We associate higher frequencies of
vibrations with faster - the faster you go, the quicker you hit the
road irregularities.

However, using a narrower tire at higher pressures also gives you
higher frequencies, and thus tricks you into feeling faster even if
you aren't. This still works for me - whenever I ride narrow tires, I
feel super-fast. Then I ask Mark, who is riding next to me on his
usual 650B x 38 mm tires whether we are going faster than usual, and
the answer always is "No." Tricked again."

http://search.bikelist.org/getmsg.as...811.0164.e ml

That's not to say Andres should not treat himself to faster tires. It
is a kick to come upon smooth concrete and find yourself going .5mph
faster than you were on asphalt. That much can be gotten out of the
fastest tires, for less than an extra $60 the pair.

Harry Travis

On Mon, 17 Nov 2008 21:57:00 -0800 (PST), Ron Ruff
wrote:

It is truly amazing... but people like to get new stuff and it helps
if they can make up a reason to justify it.

What I find amazing is that that fact makes many people in this group
biased against even trying to find equipment that let's one go a
little faster.

On Mon, 17 Nov 2008 21:57:00 -0800 (PST), Ron Ruff
wrote:

. I gained a little over 3% in speed, or 0.8 mph.

That is great.

On Nov 17, 7:00*pm, wrote:
*"Keep in mind Carl's 9.7 second calculated savings over 2.5 miles is
the difference between regular wheels, and $2,000+ super duper aero
deep section wheels. *Not $200, $2,000+. "

This is 97 seconds in a 40 K TT

Its also calculated time. Not real time. You can calculate lots of
things to turn out however you want them. Reality is always
different.



*- a serious amount of time at any
level of competition. Whether or not it's worth it to you depends on
personal finance, etc. However, this is an undeniably huge amount of
time, even in the lowest levels of amateur racing.
For training or enthusiast riding, hard to justify anything other than
a good set of conventional hand-built wheels. For racing, if you have
the money, no one can afford to give away this amount of time, even in
Cat IV/V.

On Nov 17, 7:07 pm, " wrote:

I am friends with the local shop owners. I ride with them, and I talk
bikes with them. However, I rarely buy things from them because I
rarely buy anything anyways and they don't usually have the things
that I want. Even though I am friends with them. we never talk about
components because people tend to believe all the stories that they
tell. I ride with a heavy bike and they all ride with these much
lighter bikes and they think that it makes a big deal. They tell
stories about their new wheels, forks, bikes and other stuff as it was
incredibly noticeable. Sometimes I wonder.

I don't do a lot of buying from my guys either. Partially because I
rarely buy stuff, partially because they're out of the way, etc. When
i'm in the area I always drop in, and we chat, they ask about my bikes
(only one of which I bought from them, and that was this summer, this
has been going on much longer than that). Lately I make a point of
buying a couple CO2 carts, or a tube, or both, stuff I know I'll need
anyway, since I'd rather give them my business.

There's another shop around the corner from "my shop". Hardcore
roadies, the lot of them. Ultra-light bikes all around, DA
components, etc. Sounds like the guys you're talking about. "My guy"
at "my shop" rides a bike that's built from stuff he scrounged or got
deals on working in a shop. Nothing matches, although everything
works properly together the component groups are not matched, etc.
He's not riding the latest or newest or lightest anything, but he'll
ride the pants off most people I know. He's also one of the few shop
employees whose initial reaction to my older MTB was completely
positive. He's never tried to sell me an upgrade, although he has
commented that it's clear I ride the snot out of it, and that's good,
because that's what bikes are for.

I remember when I raced BMX the difference between a win and third
place was often less than a bike length. Of course, the moto’s were
about a minute long, but the concept remains. If you're racing, that
extra fraction of a MPH or few seconds shaved can make a serious
difference. If you're just riding, probably not so much.


I played with the analytic cycling chart and saw that riding against a
15 mph wind for 20 miles you can get some advantage with a more aero
wheel. I don't know if I would be able to feel it though.- Hide quoted text -

Some advantage? Sure. One you can feel? I'd expect that depends how
carefully you watch your computer. Then there's the mental aspect, if
you know you have changed something on your bike that should give you .
5MPH, and you're expecting that .5MPH, and used to riding hard anyway,
I'd be surprised if you didn't produce that extra .5MPH, new
components or placebo. For me, I'd have to be racing for it to be
worth it. I could save substantially more time on one of my typical
longer rides by pulling into and out of my rest stops faster, or not
sitting up and checking out the sights so often, or not stopping to
fiddle with my MP3 player, etc. I do rides sometimes where I'm head-
down hauling-the-mail, and I don't stop for things like switching a
song or sitting by a river for a few. Even on those rides I'm not
above relaxing for a moment to take in some scenery. I imagine I'd
have to dedicate 100% of my ride to being as fast as possible in order
to justify an upgrade like aero wheels. Right now even my "fast
rides" are probably only 95% dedicated to going fast. I can't see
bringing that # to 100% unless I were to start racing again. Knowing
me, even in a race I’d let my form stray momentarily for certain bits
of scenery, although it would probably be more like 99% focused mail-
hauling then. There are certain things I’m just not wired to not
notice & look at, no matter what I’m doing. There’s a certain type of
car, motorcycle, woman, airplane, dirt bike and boat that’s going to
catch my eye and cost me a few seconds of concentration no matter what
I’m doing. Passing any one of those things could likely negate the
advantage of my new aero wheels.

Although since I’d look no matter what I was riding, I suppose I’d
still be a touch faster w/ the faster wheels. Still, I’d be more
likely to try not to allow such distractions to cost me a second or
two here or there than I would be to spend hundreds on a wheel set to
save me those same seconds. And I’m not about to give up those
distractions, so I guess I’m not about to pick up that new wheel set
either.

At the end of the day I think it's all personal preference, what's
important to you and what you have to spend. I tend to make upgrades
like that when I need to upgrade anyway. If I were building a new
wheel set because I needed one, I’d certainly consider more aero
wheels and blade spokes. I think it’s nice my bike came with semi-
aero wheels with a fairly low spoke count that still manage to hold up
to my abuse. Still, if it had plain old box-section wheels, I’d ride
them until there was a need to replace them before considering going
for something more aero.

Ron Ruff wrote:
I gained a little over 3% in speed, or 0.8 mph.

You bought the equivalent of a 10% increase in FTP. If you have the
checkbook balance to spare (and you weren't financing it with a HELOC that
I'm going to have to bail you out of), then why not?

John Forrest Tomlinson schreef:
On Mon, 17 Nov 2008 21:57:00 -0800 (PST), Ron Ruff
wrote:

It is truly amazing... but people like to get new stuff and it helps
if they can make up a reason to justify it.

What I find amazing is that that fact makes many people in this group
biased against even trying to find equipment that let's one go a
little faster.


It is because the OP asked the wrong question. That question can only be
answered with opinions.

'If I got a wheels with 28 to 30 mm rims and 16 to 24 aero spokes,
will I feel a difference at speeds over 20mph?'

What kind of question is that? Who cares if you can feel the difference?
It doesn't matter. Auro wheels are faster. Period. It is measured over
and over again.

Lou