the aerodynamic wheel for the rest of us?

[Fred Clydesdale]

i've been following with great interest the discussion concerning
zipps & drag & how they compare to "old fashioned" wheels. big
differences between them and my 36h MA-40's, i'm sure.

at 30mph.

show of hands: how many of you cruise at 30mph? okay, if i take
that figure and divide by 2 i'll probably get a much more reliable
figure.

my question is: how do they compare at, say, 18mph (to choose a
completely random speed that isn't at all my own pitiful cruising
speed)? 20mph? i'm sure that (1) the differences are considerably
smaller and (2) the aero portion of the equation itelf is considerably
smaller at that speed as well. anybody have pointers to reliable
data for other speeds?

 

[Andrew F Martin]

Fred Clydesdale wrote:
> i've been following with great interest the discussion concerning
> zipps & drag & how they compare to "old fashioned" wheels. big
> differences between them and my 36h MA-40's, i'm sure.
>
> at 30mph.
>
> show of hands: how many of you cruise at 30mph? okay, if i take
> that figure and divide by 2 i'll probably get a much more reliable
> figure.
>
> my question is: how do they compare at, say, 18mph (to choose a
> completely random speed that isn't at all my own pitiful cruising
> speed)? 20mph? i'm sure that (1) the differences are considerably
> smaller and (2) the aero portion of the equation itelf is considerably
> smaller at that speed as well. anybody have pointers to reliable
> data for other speeds?

These wheels are designed to support the racer base who benefit from
the advantages at 25-30mph. They are MARKETED to people to cruise at
15mph. Sure they have some benefit, but as you mention - it is of
significantly deminished value.

 

[Kinky Cowboy]

On 22 Aug 2006 14:56:28 -0700, "Andrew F Martin"
<[email protected]> wrote:

>
>Fred Clydesdale wrote:
>> i've been following with great interest the discussion concerning
>> zipps & drag & how they compare to "old fashioned" wheels. big
>> differences between them and my 36h MA-40's, i'm sure.
>>
>> at 30mph.
>>
>
>These wheels are designed to support the racer base who benefit from
>the advantages at 25-30mph. They are MARKETED to people to cruise at
>15mph. Sure they have some benefit, but as you mention - it is of
>significantly deminished value.

Just for clarification; elites and pros who do 30mph averages in time
trials are 'cruising' on the flats at 32-35mph.

I don't see much evidence that Zipp etc are marketing to the 15mph
crowd, but anybody that slow who's enough of a sucker to buy high zoot
aero wheels is doing their bit to support pro cycling; whether or not
that's a good thing is, perhaps, moot now that we are getting a
clearer idea of exactly what pro cycling consists of
Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary

 

[Ron Ruff]

Fred Clydesdale wrote:
> anybody have pointers to reliable
> data for other speeds?

Aero will dominate even at low speeds (like 18-20mph). To illustrate:

Total weight = 190 lb
Transmission eff.= 96%
Crr= .005
Density= 1.179 kg/m^3
CdA= .32m^2 (a good low position, not TT)

400W output, V = 27.03 mph
if CdA= .30 (deep aero wheels), V= 27.59 mph
V improvement = 2.07%

150W output, V = 18.62 mph
if CdA= .30, V= 18.99 mph
V improvement = 1.99%

So... the percentage effect on speed is nearly the same.

 

[Booker C. Bense]

-----BEGIN PGP SIGNED MESSAGE-----

In article <[email protected]>,
Fred Clydesdale <[email protected]> wrote:
>i've been following with great interest the discussion concerning
>zipps & drag & how they compare to "old fashioned" wheels. big
>differences between them and my 36h MA-40's, i'm sure.
>
>at 30mph.
>
>show of hands: how many of you cruise at 30mph? okay, if i take
>that figure and divide by 2 i'll probably get a much more reliable
>figure.
>
>my question is: how do they compare at, say, 18mph (to choose a
>completely random speed that isn't at all my own pitiful cruising
>speed)? 20mph? i'm sure that (1) the differences are considerably
>smaller and (2) the aero portion of the equation itelf is considerably
>smaller at that speed as well. anybody have pointers to reliable
>data for other speeds?


Aerodynamic theory states that drag is proportional to the square
of the velocity. So for a given bike rider and equipment:

Drag = ( some constant ) * 900 at 30mph,

Drag = ( some constant ) * 400 at 20 mph,

Drag = ( some constant ) * 324 at 18 mph.


So if they give you a 1mph advantage at 30mph, they give you
roughly a .36 mph advantage a 18mph. This is ignoring any
other effects and is the optimal result. What actually happens
in the real world is left as an exercise for the reader.

_ Booker C. Bense

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[Ron Ruff]

Booker C. Bense wrote:
> So if they give you a 1mph advantage at 30mph, they give you
> roughly a .36 mph advantage a 18mph.

There is a fallicy in your argument. Drag at 18mph is .36 x drag at 30
mph... but the speed delta does not abide by the same ratio.

 

[Ernie Willson]

Ron Ruff wrote:
> Booker C. Bense wrote:
>
>>So if they give you a 1mph advantage at 30mph, they give you
>>roughly a .36 mph advantage a 18mph.
>
>
> There is a fallicy in your argument. Drag at 18mph is .36 x drag at 30
> mph... but the speed delta does not abide by the same ratio.
>
You are correct that the drag at 18 mph is 36% of the drag at 30 mph.
What I think really matters is the power you need to maintain these
speeds. This varies as the cube of the velocity, not the square. To
maintain 18 mph requires 21.6% of the power of maintaining 30 mph.

HTH,
EJ in NJ

 

[Qui si parla Campagnolo]

Fred Clydesdale wrote:
> i've been following with great interest the discussion concerning
> zipps & drag & how they compare to "old fashioned" wheels. big
> differences between them and my 36h MA-40's, i'm sure.
>
> at 30mph.
>
> show of hands: how many of you cruise at 30mph? okay, if i take
> that figure and divide by 2 i'll probably get a much more reliable
> figure.
>
> my question is: how do they compare at, say, 18mph (to choose a
> completely random speed that isn't at all my own pitiful cruising
> speed)? 20mph? i'm sure that (1) the differences are considerably
> smaller and (2) the aero portion of the equation itelf is considerably
> smaller at that speed as well. anybody have pointers to reliable
> data for other speeds?

I'm sure somebody will quote a website with all the differences given
in numbers that seem like a lot but are actually are not. Way to much
emphasis on equipment and as I've said more than once...4 things that
make a difference in cycling performance, a significant difference.

-Fit-bike fit ya?
-Fitness-are you fit?
-Fat-lackthereof on you
-Finesse-riding and racing smart.

 

[Sandy]

Qui si parla Campagnolo a écrit :
> Fred Clydesdale wrote:
>
>> i've been following with great interest the discussion concerning
>> zipps & drag & how they compare to "old fashioned" wheels. big
>> differences between them and my 36h MA-40's, i'm sure.
>>
>> at 30mph.
>>
>> show of hands: how many of you cruise at 30mph? okay, if i take
>> that figure and divide by 2 i'll probably get a much more reliable
>> figure.
>>
>> my question is: how do they compare at, say, 18mph (to choose a
>> completely random speed that isn't at all my own pitiful cruising
>> speed)? 20mph? i'm sure that (1) the differences are considerably
>> smaller and (2) the aero portion of the equation itelf is considerably
>> smaller at that speed as well. anybody have pointers to reliable
>> data for other speeds?
>>
>
> I'm sure somebody will quote a website with all the differences given
> in numbers that seem like a lot but are actually are not. Way to much
> emphasis on equipment and as I've said more than once...4 things that
> make a difference in cycling performance, a significant difference.
>
> -Fit-bike fit ya?
> -Fitness-are you fit?
> -Fat-lackthereof on you
> -Finesse-riding and racing smart.
>
>
Hey stop that ! You used a French word !!!

--

Bonne route !

Sandy
Verneuil-sur-Seine FR

 

[Ron Ruff]

Ernie Willson wrote:
> This varies as the cube of the velocity, not the square. To
> maintain 18 mph requires 21.6% of the power of maintaining 30 mph.

Also true... but if you want to know how much faster you can go with
aero wheels at 18mph vs 30mph (or whatever), the speed gained will be
~proportional to speed... ie the same percentage increase.

 

[Qui si parla Campagnolo]

Sandy wrote:
> Qui si parla Campagnolo a écrit :
> > Fred Clydesdale wrote:
> >
> >> i've been following with great interest the discussion concerning
> >> zipps & drag & how they compare to "old fashioned" wheels. big
> >> differences between them and my 36h MA-40's, i'm sure.
> >>
> >> at 30mph.
> >>
> >> show of hands: how many of you cruise at 30mph? okay, if i take
> >> that figure and divide by 2 i'll probably get a much more reliable
> >> figure.
> >>
> >> my question is: how do they compare at, say, 18mph (to choose a
> >> completely random speed that isn't at all my own pitiful cruising
> >> speed)? 20mph? i'm sure that (1) the differences are considerably
> >> smaller and (2) the aero portion of the equation itelf is considerably
> >> smaller at that speed as well. anybody have pointers to reliable
> >> data for other speeds?
> >>
> >
> > I'm sure somebody will quote a website with all the differences given
> > in numbers that seem like a lot but are actually are not. Way to much
> > emphasis on equipment and as I've said more than once...4 things that
> > make a difference in cycling performance, a significant difference.
> >
> > -Fit-bike fit ya?
> > -Fitness-are you fit?
> > -Fat-lackthereof on you
> > -Finesse-riding and racing smart.
> >
> >
> Hey stop that ! You used a French word !!!

I'll be more careful in le future.....
>
> --
>
> Bonne route !
>
> Sandy
> Verneuil-sur-Seine FR