More weight, faster descents??

On 2007-10-01, Mike Jacoubowsky wrote:
Is that gut fat, or a lot a abdominal muscle mass

On me? Gut fat! But for the TdF riders, what they're doing is intentionally
letting their stomach sag down, countering the natural tendancy to kinda
suck it in.

A cyclist isn't going to intentionally build abdominal muscle mass, as
it's not much good for anything having to do with cycling.

I heard Indurain's paunch was caused by his elephantine lungs displacing
all his inessential organs downwards.

On 2007-10-01, Donga wrote:
[...]
The phenomenon has to do with not even trying to go fast in a casual
ride, e.g. when we've laboured up a hill and crested it, then start to
coast down. Even if I'm sitting up, turned around chatting or gasping,
with the aerodynamics of a garden shed, I have to brake to stay with
him.

Interesting. I wonder if it's possible that you're riding in a
straighter line than him. You might subconsciously be better at
balancing meaning that compared to you he's weaving around all the time.
Have you tried swapping bikes?

On Oct 1, 8:00 pm, Ben C wrote:
On 2007-10-01, Donga wrote:
[...]

The phenomenon has to do with not even trying to go fast in a casual
ride, e.g. when we've laboured up a hill and crested it, then start to
coast down. Even if I'm sitting up, turned around chatting or gasping,
with the aerodynamics of a garden shed, I have to brake to stay with
him.

Interesting. I wonder if it's possible that you're riding in a
straighter line than him. You might subconsciously be better at
balancing meaning that compared to you he's weaving around all the time.
Have you tried swapping bikes?

Interesting theory. in case you are right, no way am I letting that
sucker on my bike!
;-)

I've been trying to figure why I accelerate faster downhill (coasting)
than my riding buddy. We are about the same weight, size, bike
position, tires. Is it my Campag Record hubs versus his Mavic Ksyrium
Elites?

Most likely not. Mavic isn't known for very aerodynamic wheels, so even if
you've got an air-churning 32-spoke shallow-dish wheel, that's not going to
be much of a difference. More likely you've got to bring you knees not just
"in" but "up", let your gut sag down to your knees (do *not* pedal!!!), and
get your chin down low, as Mr. Muzi suggested. Arms are pretty easy to
figure out, because you can actually feel the wind on the hair of your arms,
so it's not too tough to find the position where you feel that least.

If the grade is, say, 4% or greater, pedaling is probably going to slow you
down in the long run. You can try pedaling for very short periods of time
(to get your speed up if you're below 40mph), but unless you're drafting a
vehicle (or another bike) you're probably doing more harm than good.

--Mike Jacoubowsky
Chain Reaction Bicycles
www.ChainReaction.com
Redwood City & Los Altos, CA USA


"Donga" wrote in message
ups.com...
On Oct 1, 7:07 am, Mark
wrote:
DaveH wrote:
I've seen this notion in various forums. It typically takes the form
of "A heavier bike may be more work uphill, but is faster downhill due
to gravity..." Something like that.

The notion -- which I think is incorrect -- really should take the
form of "Greater total mass (rider + bike + stuff) may be more work
uphill, but is faster downhill..."

In any case, reviewing the elementary physics, doesn't mass cancel in
the equations? Same reason a rock and feather both accelerate at g in
a vacuum? Ergo, that heavier bike isn't getting you down the hill any
faster.
Dave

Why don't you go do some cycling in a vacuum and let us know how it
works out. Out here in the real world (no vacuum), heavier bikes (w/
same frontal area) go down hill faster.

Mark J.

I've been trying to figure why I accelerate faster downhill (coasting)
than my riding buddy. We are about the same weight, size, bike
position, tires. Is it my Campag Record hubs versus his Mavic Ksyrium
Elites?

Tim McNamara wrote:
In article ,
DaveH wrote:

I've seen this notion in various forums. It typically takes the form
of "A heavier bike may be more work uphill, but is faster downhill
due to gravity..." Something like that.

The notion -- which I think is incorrect -- really should take the
form of "Greater total mass (rider + bike + stuff) may be more work
uphill, but is faster downhill..."

In any case, reviewing the elementary physics, doesn't mass cancel in
the equations? Same reason a rock and feather both accelerate at g
in a vacuum? Ergo, that heavier bike isn't getting you down the hill
any faster.

No. The power to weight ratio favors the lighter rider on the way up,
and the mass to frontal area ratio favors the heavier riders on the way
down. You're not descending in a vacuum, so that issue is irrelevant.
Generally the advantage to the lighter rider when climbing is greater
than the advantage to the heavier rider on the descent- it's much easier
for the heavier rider to lose 15 minutes going uphill than to gain 15
minutes on the descent. FWIW, the mass to frontal area ration also tends
to favor larger riders in time trials, because the larger rider
generally has a higher total output.

That's about it. I'm very tall and can out coast anybody I've ever
ridden with, I'm almost a 1-man tandem. Despite having a large (68cm)
bike and no aero anything, I'm still noticeably faster in a gravity race.

Peter Cole wrote:
Tim McNamara wrote:
In article ,
DaveH wrote:

I've seen this notion in various forums. It typically takes the form
of "A heavier bike may be more work uphill, but is faster downhill
due to gravity..." Something like that.
The notion -- which I think is incorrect -- really should take the
form of "Greater total mass (rider + bike + stuff) may be more work
uphill, but is faster downhill..."
In any case, reviewing the elementary physics, doesn't mass cancel in
the equations? Same reason a rock and feather both accelerate at g
in a vacuum? Ergo, that heavier bike isn't getting you down the hill
any faster.

No. The power to weight ratio favors the lighter rider on the way up,
and the mass to frontal area ratio favors the heavier riders on the
way down. You're not descending in a vacuum, so that issue is
irrelevant. Generally the advantage to the lighter rider when climbing
is greater than the advantage to the heavier rider on the descent-
it's much easier for the heavier rider to lose 15 minutes going uphill
than to gain 15 minutes on the descent. FWIW, the mass to frontal area
ration also tends to favor larger riders in time trials, because the
larger rider generally has a higher total output.

That's about it. I'm very tall and can out coast anybody I've ever
ridden with, I'm almost a 1-man tandem. Despite having a large (68cm)
bike and no aero anything, I'm still noticeably faster in a gravity race.

I am 1/2-Chalo in mass, and still out-coast tandems. I can pick up a
couple of miles per hour extra speed by sliding to the front of the seat
and un-clipping one foot so both my legs are straight.

--
Tom Sherman - Holstein-Friesland Bovinia
A Real Cyclist [TM] keeps at least one bicycle in the bedroom.

--
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