Aerodynamics wheels and tire size??

Goldenboy said:

I was on a ride over the weekend with a friend and I noticed that he was able to hold his speed
better than me when coasting down hills. He had this advantage over the other riders in the pack as
well. He is running 30mm aero Mavic Cosmics with 18c tires. I am running 23mm Ksyrium Elites with
23c tires and he has about 40 pounds on me.

If he's 40lbs heavier, there's the answer right there.
--
David Damerell <[email hidden]> flcl?

Goldenboy said:

I was on a ride over the weekend with a friend and I noticed that he was able to hold his speed
better than me when coasting down hills. He had this advantage over the other riders in the pack
as well. He is running 30mm aero Mavic Cosmics with 18c tires. I am running 23mm Ksyrium Elites
with 23c tires and he has about 40 pounds on me.

Ding!

Quoted message said:

We are both running clichers at about 125psi. Does his setup have that much of an advantage or is
my bike underperforming?? He was able to save valuable energy while the rest of us were spinning at
the lower slopes of hills. I actually seemed to coast better than most other riders so I assume it
to be his wheel/rim combo.

Oh sure, it's his 18mm tires and deep aero rims. The 40 lbs of weight he has over you has no effect
whatsoever....

Sheesh.

--

David L. Johnson

__o | Become MicroSoft-free forever. Ask me how. _`\(,_ | (_)/ (_) |

Goldenboy may have said:

I was on a ride over the weekend with a friend and I noticed that he was able to hold his speed
better than me when coasting down hills. He had this advantage over the other riders in the pack as
well. He is running 30mm aero Mavic Cosmics with 18c tires. I am running 23mm Ksyrium Elites with
23c tires and he has about 40 pounds on me. We are both running clichers at about 125psi. Does his
setup have that much of an advantage or is my bike underperforming?? He was able to save valuable
energy while the rest of us were spinning at the lower slopes of hills. I actually seemed to coast
better than most other riders so I assume it to be his wheel/rim combo.

If he's 40 pounds heavier, there's most of your answer. On the other hand, he has to haul that extra
40 pounds *up* the slopes, too. TANSTAAFL.

---
My email address is antispammed; pull WEEDS if replying via e-mail.

Yes, I have a killfile. If I don't respond to something, it's also possible that I'm busy.

Yes he is 40 pounds heavier. But so were many other riders, and then some. I could roll just as well as them if not better. But 'DING' oh yeah, I put that in the original post but you must not have read the whole thing. It is NOT that simple, but I guess on here -- everyone is an expert.

Goldenboy said:

Yes he is 40 pounds heavier. But so were many other riders, and then some. I could roll just as
well as them if not better. But 'DING' oh yeah, I put that in the original post but you must not
have read the whole thing. It is NOT that simple, but I guess on here -- everyone is an expert.

I look forward to Goldenboy's explanation of how hub bearing friction overwhelms all other forces.

--
Ted Bennett Portland OR

Goldenboy said:

Yes he is 40 pounds heavier. But so were many other riders, and then some. I could roll just as
well as them if not better. But 'DING' oh yeah, I put that in the original post but you must not
have read the whole thing. It is NOT that simple, but I guess on here -- everyone is an expert.

Now, don't get your knickers in a knot. You did not say that you rolled as fast as other riders who
were as heavy as the guy in question.

The thing is, a hefty gain in mass, for a modest gain in drag, is going to have a whole lot more
impact on descending speed than a couple of millimeters in tire width, or a more aero rim. Look at
the size of the tire and wheel's cross section. It just isn't big enough to make that much
difference on downhilling.

I usually outdistance by far most of the riders I ride with on downhills. Part of that is certainly
my avoirdupois advantage, and the rest is the fact that I learned how to downhill when I was young
and immortal, so I am less timid than most. But the width of my tires is irrelevant.

--

David L. Johnson

__o | I don't believe you, you've got the whole damn thing all wrong. _`\(,_ | He's not the kind
you have to wind-up on Sundays. --Ian (_)/ (_) | Anderson

Goldenboy said:

Yes he is 40 pounds heavier. But so were many other riders, and then some. I could roll just as
well as them if not better.

Then something's suboptimal with their machines. If this guy's 40lbs heavier than you and has
nothing wrong with his bike, there's nothing that can make you coast downhill as fast on an upright
as he will.

Quoted message said:

It is NOT that simple,

It _is_ that simple, actually.
--
David Damerell <[email hidden]> Kill the tomato!

"David Damerell" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Goldenboy said:

Yes he is 40 pounds heavier. But so were many other riders, and then some. I could roll just as
well as them if not better.

Then something's suboptimal with their machines. If this guy's 40lbs heavier than you and has
nothing wrong with his bike, there's nothing that can make you coast downhill as fast on an
upright as he will.

With a really good tuck position and semi-aero equipment, I can coast downhill as fast as friends
who outweigh my by 40 lbs, but who pay less attention to aerodynamic details. However, when one or
more of them minimizes their drag by also assuming a really good tuck, they will pull away from me -
even on box section wheels.

To state it another way: 40 lbs is a lot, but it doesn't *necessarily* guarantee that somebody will
outcoast you.

Andy Coggan

David Damerell said:

Goldenboy said:

Yes he is 40 pounds heavier. But so were many other riders, and then some. I could roll just as
well as them if not better.

Then something's suboptimal with their machines. If this guy's 40lbs heavier than you and has
nothing wrong with his bike, there's nothing that can make you coast downhill as fast on an upright
as he will.

Quoted message said:

It is NOT that simple,

It _is_ that simple, actually.

Guess that's why they call them the LAWS of physics, huh?

Mark Hickey Habanero Cycles habcycles.comhabcycles.comOpen ↗ Home of the $695 ti frame

Andy Coggan said:

With a really good tuck position and semi-aero equipment, I can coast downhill as fast as friends
who outweigh my by 40 lbs, but who pay less attention to aerodynamic details. However, when one or
more of them minimizes their drag by also assuming a really good tuck, they will pull away from me
- even on box section wheels.

If anyone can out coast Andy on a less aero bike, you KNOW they're being helped by their weight.

For a matter of comparison, a friend of mine who outweighs me by around 20 pounds (9kg) and I did a
roll test down a steep hill on our almost identical Habaneros once, swapping wheels on the
alternate runs.

With aero wheels (Shamals), I could hang right beside him.

With my light box section "climbing wheels", he easily dropped away from me.

Or to put it another way (oversimplifying and leaving out a host of variables), it appears that 20
pounds is about as much an advantage as aero wheels when coasting down that particular hill.

Mark Hickey Habanero Cycles habcycles.comhabcycles.comOpen ↗ Home of the $695 ti frame

Quoted message said:

Quoted message said:

With a really good tuck position and semi-aero equipment, I can coast downhill as fast as friends
who outweigh my by 40 lbs, but who pay less attention to aerodynamic details. However, when one
or more of them minimizes their drag by also assuming a really good tuck, they will pull away
from me - even on box section wheels.

If anyone can out coast Andy on a less aero bike, you KNOW they're being helped by their weight.

For a matter of comparison, a friend of mine who outweighs me by around 20 pounds (9kg) and I did
a roll test down a steep hill on our almost identical Habaneros once, swapping wheels on the
alternate runs.

With aero wheels (Shamals), I could hang right beside him.

With my light box section "climbing wheels", he easily dropped away from me.

Or to put it another way (oversimplifying and leaving out a host of variables), it appears that 20
pounds is about as much an advantage as aero wheels when coasting down that particular hill.

Mark Hickey Habanero Cycles habcycles.comhabcycles.comOpen ↗ Home of the $695 ti frame

...and people still wonder about aero wheels...

Mike