Bike aerodynamics / weight

[Larry]

Any comments on why everyone is so concerned with saving a few grams and you
hear very little about the aerodynamic advantage of a bike frame and
components. It is so critical in time trialing and yet most bikes are round
tubes glued to round parts. I am mostly referring to high end carbon frames.
I can't tell the difference when riding with 2 full water bottles or 2
empty ones ( 2 - 3 pounds). I can however feel a slight improvement when
riding 20 + MPH with a frame I have that is quite aerodynamic, not one round
part on it but the steering tube.

 

[Phil Holman]

"Larry" <[email protected]> wrote in message
news:[email protected]...
> Any comments on why everyone is so concerned with saving a few grams
> and you hear very little about the aerodynamic advantage of a bike
> frame and components. It is so critical in time trialing and yet most
> bikes are round tubes glued to round parts. I am mostly referring to
> high end carbon frames. I can't tell the difference when riding with 2
> full water bottles or 2 empty ones ( 2 - 3 pounds). I can however
> feel a slight improvement when riding 20 + MPH with a frame I have
> that is quite aerodynamic, not one round part on it but the steering
> tube.
>

I doubt it. Without a computer you would never tell the difference
between 22 and 23 mph. Besides, there are many other variables that
overshadow the benefit of aero tubing.

Phil H

 

[[email protected]]

Larry wrote:
> Any comments on why everyone is so concerned with saving a few grams and you
> hear very little about the aerodynamic advantage of a bike frame and
> components. It is so critical in time trialing and yet most bikes are round
> tubes glued to round parts. I am mostly referring to high end carbon frames.
> I can't tell the difference when riding with 2 full water bottles or 2
> empty ones ( 2 - 3 pounds). I can however feel a slight improvement when
> riding 20 + MPH with a frame I have that is quite aerodynamic, not one round
> part on it but the steering tube.

Shhh! As long as my competition is obsessed with light weight, I can
keep my aero advantage.

 

[JeffWills]

Larry wrote:
> I can however feel a slight improvement when
> riding 20 + MPH with a frame I have that is quite aerodynamic, not one round
> part on it but the steering tube.

I really doubt you could tell the difference in speed between a "round
tube" bike and an "aero tube" bike without a wind tunnel. Your body
accounts for the vast majority of the aero drag, and small changes in
body position can have major changes in speed.

Jeff

 

[Ron Ruff]

Larry wrote:
> Any comments on why everyone is so concerned with saving a few grams and you
> hear very little about the aerodynamic advantage of a bike frame and
> components. It is so critical in time trialing and yet most bikes are round
> tubes glued to round parts.

People are obsessed with weight because it is easier to measure...
don't need a multi-million dollar wind tunnel... a $20 scale will work
fine.

There is a Sufi parable that illustrates this... something about losing
a coin in the alley, but looking for it under a street lamp because the
light is better...

BTW, people who do TTs worry about aero a lot.

 

[cat0020]

Real aerodynamic advantage:



http://www.wisil.recumbents.com/wisil/racing2006/waterford/hunn/Waterford.12.jpg

 

[Jim Higson]

Ron Ruff wrote:

>
> Larry wrote:
>> Any comments on why everyone is so concerned with saving a few grams and
>> you hear very little about the aerodynamic advantage of a bike frame and
>> components. It is so critical in time trialing and yet most bikes are
>> round tubes glued to round parts.
>
> People are obsessed with weight because it is easier to measure...
> don't need a multi-million dollar wind tunnel... a $20 scale will work
> fine.

It is a bit like how speed rules are enforced on the roads more routinely
than agressive driving rules. It is a property that you can easily put a
number to, so it is easy to compare.

I think that all the component makers publishing weights contributes towards
it as well. If a someone looking for parts on an online shop sees they list
the weight, it encourages a culture of cyclists thinking weight is
something they should consider when buying parts (while for most people it
doesn't really matter all that much within reason)

At least the worry about weight lets component makers make good, but
slightly heavier bits in their lower range, which I can then buy for not
very much money.

> There is a Sufi parable that illustrates this... something about losing
> a coin in the alley, but looking for it under a street lamp because the
> light is better...
>
> BTW, people who do TTs worry about aero a lot.

 

[[email protected]]

cat0020 wrote:
> Real aerodynamic advantage:
>
> http://www.wisil.recumbents.com/wisil/racing2006/waterford/hunn/Waterford.12.jpg

Both banned by the UCI, the recumbent since the 1930s.

 

[Art Harris]

Larry wrote:
> Any comments on why everyone is so concerned with saving a few grams and you
> hear very little about the aerodynamic advantage of a bike frame and
> components.

Because climbing hills is the hardest thing to do and aerodynamics
don't help there. Also, few riders cruise at 25+ mph where aerodynamics
really matters.

Art Harris

 

[Skippy]

"Art Harris" <[email protected]> wrote in message
news:[email protected]...
> Larry wrote:
>> Any comments on why everyone is so concerned with saving a few grams and
>> you
>> hear very little about the aerodynamic advantage of a bike frame and
>> components.
>
> Because climbing hills is the hardest thing to do and aerodynamics
> don't help there. Also, few riders cruise at 25+ mph where aerodynamics
> really matters.
>
> Art Harris
>

Where does the 'magic' 25MPH come from? I've seen it quoted, especially
when comparing aero/non aero kit. Is it the benchmark for a reasonable
TTer?

On the flat, every rider's cruising speed is limited by wind drag.

Skippy
27MPH, head down ;-)

E&OE

 

[Skippy]

"Ron Ruff" <[email protected]> wrote in message
news:[email protected]...
>
> Larry wrote:
>> Any comments on why everyone is so concerned with saving a few grams and
>> you
>> hear very little about the aerodynamic advantage of a bike frame and
>> components. It is so critical in time trialing and yet most bikes are
>> round
>> tubes glued to round parts.
>
> People are obsessed with weight because it is easier to measure...
> don't need a multi-million dollar wind tunnel... a $20 scale will work
> fine.
>
> There is a Sufi parable that illustrates this... something about losing
> a coin in the alley, but looking for it under a street lamp because the
> light is better...
>
> BTW, people who do TTs worry about aero a lot.
>

Turn up at a TT with your 'pointy' bike and you'll still have people asking
'how much does it weigh?'. I really annoyed a guy once by admitting that I
didn't know.

I agree that it is near impossible to accurately and reliably measure drag
yourself, so you're left with weight and colour! (Red is fastest, followed
by black ;-) )

Skippy
E&OE

 

[[email protected]]

Larry wrote:
> Any comments on why everyone is so concerned with saving a few grams and you
> hear very little about the aerodynamic advantage of a bike frame and
> components. It is so critical in time trialing and yet most bikes are round
> tubes glued to round parts. I am mostly referring to high end carbon frames.
> I can't tell the difference when riding with 2 full water bottles or 2
> empty ones ( 2 - 3 pounds). I can however feel a slight improvement when
> riding 20 + MPH with a frame I have that is quite aerodynamic, not one round
> part on it but the steering tube.

The bike and parts are a minimal, minimal, minimal part of drag. What
is the largest part on a bike? Weight and surface area? The rider.
It takes effort and work on the rider's part to ride the drops, ride in
a very small hunched up position, ride to minimize surface area
presented to the front, etc. This is free for the most part. Hard to
sell free. It also requires a change, maybe radical change, by the
rider. Its harder to sell radical change on the rider's part and work
required by the rider, than it is to sell free.

 

[Peter Cole]

Skippy wrote:
> "Art Harris" <[email protected]> wrote in message
> news:[email protected]...
>> Larry wrote:
>>> Any comments on why everyone is so concerned with saving a few grams and
>>> you
>>> hear very little about the aerodynamic advantage of a bike frame and
>>> components.
>> Because climbing hills is the hardest thing to do and aerodynamics
>> don't help there. Also, few riders cruise at 25+ mph where aerodynamics
>> really matters.
>>
>> Art Harris
>>
>
> Where does the 'magic' 25MPH come from? I've seen it quoted, especially
> when comparing aero/non aero kit. Is it the benchmark for a reasonable
> TTer?
>

It is that (roughly), but aero drag power losses go up as the cube of
speed -- so it gets disproportionately more important as you go faster.


> On the flat, every rider's cruising speed is limited by wind drag.

As Art points out, most people get dropped on climbs, both in road
racing and fast club rides. When you're drafting in a pack aerodynamics
isn't too important.


> Skippy
> 27MPH, head down ;-)

Be careful, one guy in our club just rear-ended a car that way.

 

[Ron Ruff]

Art Harris wrote:
> Because climbing hills is the hardest thing to do and aerodynamics
> don't help there. Also, few riders cruise at 25+ mph where aerodynamics
> really matters.

Aero drag dominates even at 10mph on the flat... of course most of us
aren't working too hard then anyway, so we don't care.

I looked into a comparison of aero rims vs light rims for climbing
awhile back. It turns out that the small aero advantage of a 30mm rim
more than compensates for it's extra ~100g weight on a hill with less
than 8% grade.

 

[[email protected]]

Ron Ruff writes:

>> Because climbing hills is the hardest thing to do and aerodynamics
>> don't help there. Also, few riders cruise at 25+ mph where
>> aerodynamics really matters.

> Aero drag dominates even at 10mph on the flat... of course most of
> us aren't working too hard then anyway, so we don't care.

> I looked into a comparison of aero rims vs light rims for climbing
> awhile back. It turns out that the small aero advantage of a 30mm
> rim more than compensates for it's extra ~100g weight on a hill with
> less than 8% grade.

Aerodynamics of a bicycle is largely imaginary, the drag of rider
cross section being so enormously greater compared to shape changes on
the bicycle that have an effect two orders of magnitude smaller...
with tear-drop shaped tubing, rims and spokes. Those % improvements
are often touted alone rather than as their % of the composite of
rider and bicycle... where it is closer zero.

Of course, we are all Walter Mitty, riding as fast as the average
speed of the TdF, seconds saved making a difference in our live$$.

Jobst Brandt

 

[DougC]

[email protected] wrote:
> cat0020 wrote:
>> Real aerodynamic advantage:
>>
>> http://www.wisil.recumbents.com/wisil/racing2006/waterford/hunn/Waterford.12.jpg
>
> Both banned by the UCI, the recumbent since the 1930s.
>

Yea, but,,,, what sort of racing is it when an average club-level rider
on an IHPVA bike can beat top-level riders on UCI-legal bikes?

Damn sorry racing, by my figuring.
They might as well go back to hobby-horses.
~

 

[[email protected]]

DougC wrote:
> [email protected] wrote:
> > cat0020 wrote:
> >> Real aerodynamic advantage:
> >>
> >> http://www.wisil.recumbents.com/wisil/racing2006/waterford/hunn/Waterford.12.jpg
> >
> > Both banned by the UCI, the recumbent since the 1930s.
> >
>
> Yea, but,,,, what sort of racing is it when an average club-level rider
> on an IHPVA bike can beat top-level riders on UCI-legal bikes?

That's not much different than asking why there are different classes
in auto racing. Why have displacement limits? Why restrict Formula 1
and Indy to open wheels? Why have NASCAR at all, with production car
look-alikes?

The solution is the same: If you don't like the rules in one class,
find a class you like, and either participate or spectate there.

- Frank Krygowski

 

[Ron Ruff]

[email protected] wrote:
> Aerodynamics of a bicycle is largely imaginary, the drag of rider
> cross section being so enormously greater compared to shape changes on
> the bicycle that have an effect two orders of magnitude smaller...
> with tear-drop shaped tubing, rims and spokes. Those % improvements
> are often touted alone rather than as their % of the composite of
> rider and bicycle... where it is closer zero.

The rider's body generally accounts for 70-80% of the drag, the bike
making up the rest. Quite a lot of effort is spent to reduce both
components, among those who are serious about maximizing their speed in
TTs. Of course, the sellers of things like to exaggerate (and even lie
about) the benefits of their products. I'm thinking of the current
ceramic bearing craze...

A more ecomonical approach would be to use whatever equipment you have,
and calculate what your time would have been if you'd spent x$ on
better equipment. If it would make a meaningful difference in your
cycling "career", then maybe...

> Of course, we are all Walter Mitty, riding as fast as the average
> speed of the TdF, seconds saved making a difference in our live$$.

There are worse fantasies that could be indulged in...

Most of the people I know of who race frequently and are obsessed about
these things, seem to have a healthy enjoyment of the sport. They are
merely trying to maximize their performance in a competitive
environment. They may not have the physical gifts to be a pro, but they
can still enjoy the attempt to maximize the potential they have.

 

[Larry]

This is all exactly my point there is minimal effect from a aero bike but
most of the time you are not climbing hills for the cumulative advantage
should be greater. If you have a 160 lb. rider and a 15 lb bike a 17 lb bike
is only 1% heaver and what percentage of time are you climbing? And yes my
aero frame which is UCI legal is red and black so it must be the reason I
feel faster.

 

[Ozark Bicycle]

Peter Cole wrote:
> Skippy wrote:
> > "Art Harris" <[email protected]> wrote in message
> > news:[email protected]...
> >> Larry wrote:
> >>> Any comments on why everyone is so concerned with saving a few grams and
> >>> you
> >>> hear very little about the aerodynamic advantage of a bike frame and
> >>> components.
> >> Because climbing hills is the hardest thing to do and aerodynamics
> >> don't help there. Also, few riders cruise at 25+ mph where aerodynamics
> >> really matters.
> >>
> >> Art Harris
> >>
> >
> > Where does the 'magic' 25MPH come from? I've seen it quoted, especially
> > when comparing aero/non aero kit. Is it the benchmark for a reasonable
> > TTer?
> >
>
> It is that (roughly), but aero drag power losses go up as the cube of
> speed -- so it gets disproportionately more important as you go faster.
>
>
> > On the flat, every rider's cruising speed is limited by wind drag.
>
> As Art points out, most people get dropped on climbs, both in road
> racing and fast club rides. When you're drafting in a pack aerodynamics
> isn't too important.
>
>
> > Skippy
> > 27MPH, head down ;-)
>
> Be careful, one guy in our club just rear-ended a car that way.



By the first name of Davis, by any chance?