question of weight on a bike

On 23 Feb, 16:36, raamman wrote:
Galileo theorized equal acceleration of bodies of different mass; this
was later demonstrated on the moon where a feather and a hammer were
dropped and fell at the same rate; he was persectuted by the catholic
church some 400 years ago. It astounds me to no end that people
continually repeat the notion that heavier objects fall faster. They
don't.It is a physical law.

Are you religious, or what?

Sergio
Pisa

On Feb 23, 12:59*pm, sergio wrote:
On 23 Feb, 16:36, raamman wrote:

Galileo theorized equal acceleration of bodies of different mass; this
was later demonstrated on the moon where a feather and a hammer were
dropped and fell at the same rate; he was persectuted by the catholic
church some 400 years ago. It astounds me to no end that people
continually repeat the notion that heavier objects fall faster. They
don't.It is a physical law.

Are you religious, or what?

Sergio
Pisa

not in the slightest

On Feb 23, 12:51*pm, Jobst Brandt wrote:
Raam Man wrote anonymously:





I am not an engineer but I gather lighter bikes help climbing but
what about on the flats. *In other words I ride around the
flatlands here no real hills a few ups over the bridges, does
weight become almost non issue within reason.
In other words on a road bike that weights say 21 pounds, is there
any real advantage if the bike is say 20, 19, 18, or 17 pounds? *If
your bike weighs a little more do you generate more speed going
down? *I really don't know this but it does seem if the bike is
heavier I should go down faster. *At what point do you think it
would matter in weight or does that all have to do with big hills
and long grades up the mountain. *I could see this being an
advantage to have a light bike.
If I ride say a 50 mile route or time trial for 2.5 hours would I
gain much having a bike that weighs less on a flat course or just
gentle rolling hills. *Any idea the difference? *Naturally it is
all in the engine and if you want to get faster you need to work
the engine but I just wondered.
I ask this because my road bike weighs 21 pounds fully load with
pedals and 2 h20s cages in a 61 cm size. *I really don't need to
lose weight so do give me that option. *I am not looking to get rid
of bike weight just want the facts on this.
Galileo theorized equal acceleration of bodies of different mass;
this was later demonstrated on the moon where a feather and a hammer
were dropped and fell at the same rate; he was persecuted by the
catholic church some 400 years ago. *It astounds me to no end that
people continually repeat the notion that heavier objects fall
faster. *They don't. *It is a physical law.

Get off the law angle and consider other aspects of the mass of an
object. *Think about why the experiment was performed on the moon
(effectively in a vacuum). *Bicycles are not ridden in a vacuum so air
resistance and tire rolling resistance enter the effect of greater or
lesser mass of bicycle and rider.

I suspect you don't ride a bicycle or you would be aware that heavier
riders coast downhill faster than light ones. *

sad to see your resort to a slight against me; I don't ride with
others because they hold me back

BTW, who are you that
you hide behind a pseudonym?


you have no need to know

Jobst Brandt- Hide quoted text -

- Show quoted text -

bye bye

raamman wrote:
Galileo theorized equal acceleration of bodies of different mass; this
was later demonstrated on the moon where a feather and a hammer were
dropped and fell at the same rate; he was persectuted by the catholic
church some 400 years ago. It astounds me to no end that people
continually repeat the notion that heavier objects fall faster. They
don't.It is a physical law.

sergio wrote:
Are you religious, or what?


The whole sad thing was a mess of politics and not as clear
cut as the current grammar school version:
http://www.law.umkc.edu/faculty/proj...eoaccount.html

Galileo served two days of his sentence.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

Peter Cole wrote:
Mark Cleary wrote:
I am not an engineer but I gather lighter bikes help climbing but what
about on the flats. In other words I ride around the flatlands here no
real hills a few ups over the bridges, does weight become almost non
issue within reason.

In other words on a road bike that weights say 21 pounds, is there any
real advantage if the bike is say 20, 19, 18, or 17 pounds? If your
bike weighs a little more do you generate more speed going down? I
really don't know this but it does seem if the bike is heavier I
should go down faster. At what point do you think it would matter in
weight or does that all have to do with big hills and long grades up
the mountain. I could see this being an advantage to have a light bike.

If I ride say a 50 mile route or time trial for 2.5 hours would I gain
much having a bike that weighs less on a flat course or just gentle
rolling hills. Any idea the difference? Naturally it is all in the
engine and if you want to get faster you need to work the engine but I
just wondered.

I ask this because my road bike weighs 21 pounds fully load with
pedals and 2 h20s cages in a 61 cm size. I really don't need to lose
weight so do give me that option. I am not looking to get rid of bike
weight just want the facts on this.

If you get into time trials you'll find that it's all about
aerodynamics. It takes a lot of tweaking and practice to get really aero
on a bike, and it makes a huge (real, not psychological) difference.

Yes, aero makes a huge difference.

Keep in mind, though: the vast majority of aerodynamic improvements can
be had with a set of cheap clip-on aero bars (well, that and adjusting
your existing equipment to improve position). That's definitely the
number one biggest improvement you can make to aerodynamics, by far the
most bang for the buck. That aero water bottle will make about as much
difference as dropping a pound off your frame (for a flat ride), i.e.
pretty negligible, as noted in other postings here.

I went to a regional TT last Sunday. Amazing the amount of aero bling
out there (funny bikes, aero helmets galore, etc.) - but most of them on
people who appeared not to TT much (they weren't pros or apparently
triathletes, and there aren't many other TTs in this region). It's your
money, spend it how you like, but after the aero bars, the next speed
improvement you can buy will cost a lot more per unit of improvement.

Mark J.

On 23 Feb, 19:28, AMuzi wrote:
Are you religious, or what?
The whole sad thing was a mess of politics and not as clear
cut as the current grammar school version:http://www.law.umkc.edu/faculty/proj...o/galileoaccou...

That was not what I meant.
Raamman seems to hold unfounded beliefs in history and science, both.

Sergio
Pisa

On Feb 23, 12:13*pm, raamman wrote:
I suspect you don't ride a bicycle or you would be aware that heavier
riders coast downhill faster than light ones. *

sad to see your resort to a slight against me; I don't ride with
others because they hold me back

I find raamman's retort amusing.
There could be other reasons he rides alone.

Sergio Moretti

Mark Cleary wrote:
I ask this because my road bike weighs 21 pounds fully load with pedals
and 2 h20s cages in a 61 cm size.


To get an idea of how much difference a pound or two would make, try
riding with only one (or no) water bottle. I doubt you will notice a
difference, even when climbing.

Art Harris

On Feb 23, 8:10*am, Frank Krygowski wrote:
On Feb 23, 8:27*am, Tad McClellan wrote:

Mark Cleary wrote:
but it does seem if the bike is heavier I should go down
faster.

That is what Aristotle thought too.

Galilieo disproved it.

(hopefully he can be believed nowadays g )

As someone else mentioned, what you're apparently claiming - that all
objects go downhill with the same acceleration - is true ONLY if air
resistance is negligible. *Dropping a 14 pound and a 16 pound bowling
ball off your roof? *Fine. *Riding a bike on the Moon? *Perfect.

Riding a bike on earth? *No way. *Above maybe 15 mph, air resistance
is the main thing you're fighting while on a bike. *The more weight
you have, the more gravity fights the air resistance on a downhill;
the faster you coast.

We had a very, very heavy guy in our bike club. *He was super slow
uphill, but he was untouchable on a good downhill. *And anyone who's
ridden a tandem, or tried to keep up with one downhill, knows about
this.

It's like simultaneously dropping a bowling ball and a feather.

You also have to factor in that larger guys tend to have larger
frontal profiles -- so just being big is not a guaranty of getting to
the bottom first. My wife was an excellent racer and particularly a
good climber, but she was slow downhill because she was tall and lean
-- like a sail, even though she was heavier than a lot of the girls.
-- Jay Beattie.

On 23 Feb, 17:57, wrote:
On Tue, 23 Feb 2010 07:36:35 -0800 (PST), raamman
wrote:



On Feb 22, 11:06 pm, Mark Cleary wrote:
I am not an engineer but I gather lighter bikes help climbing but what
about on the flats. In other words I ride around the flatlands here no
real hills a few ups over the bridges, does weight become almost non
issue within reason.

In other words on a road bike that weights say 21 pounds, is there any
real advantage if the bike is say 20, 19, 18, or 17 pounds? If your bike
weighs a little more do you generate more speed going down? I really
don't know this but it does seem if the bike is heavier I should go down
faster. At what point do you think it would matter in weight or does
that all have to do with big hills and long grades up the mountain. I
could see this being an advantage to have a light bike.

If I ride say a 50 mile route or time trial for 2.5 hours would I gain
much having a bike that weighs less on a flat course or just gentle
rolling hills. Any idea the difference? Naturally it is all in the
engine and if you want to get faster you need to work the engine but I
just wondered.

I ask this because my road bike weighs 21 pounds fully load with pedals
and 2 h20s cages in a 61 cm size. I really don't need to lose weight so
do give me that option. I am not looking to get rid of bike weight just
want the facts on this.
--
Deacon Mark Cleary
Epiphany Roman Catholic Church

Galileo theorized equal acceleration of bodies of different mass; this
was later demonstrated on the moon where a feather and a hammer were
dropped and fell at the same rate; he was persectuted by the catholic
church some 400 years ago. It astounds me to no end that people
continually repeat the notion that heavier objects fall faster. They
don't.It is a physical law.

Dear R,

In a vacuum, feathers and hammers fall at the same rate.

In air, the heavier object with the same frontal area and wind drag
hits the ground much sooner.

For bicyclists, mass increases faster than wind drag and rolling
resistance, so a heavier bicycle and rider coasts faster downhill.

Here's a typical bicycle speed calculator that includes those factors
and lets you compare things side by side:
*http://bikecalculator.com/veloUS.html

With the defaults, the two riders go 15.00 mph on level ground by
putting 100 watts into the pedals.

Down a -6% grade, their predicted speed, assisted by their 100 watt
effort, rises to 32.51 mph.

Turn one of the 150 lb riders into a 180 lb rider, and the extra 30
pounds increases his speed to 34.74 mph, 2.23 mph faster.

That extra 2.23 mph doesn't sound like much.

But at 34.74 mph, wind drag and rolling resistance increase so much
that the lighter rider has to put out 220 watts to catch up with the
heavier rider putting out only 100 watts--more than twice as much
power.

Increase the heavy rider to 220 pounds, and the extra 70 pounds
increases his speed to 37.55 mph, 5.05 mph faster.

At 37.55 mph, wind drag and rolling resistance are so powerful that
the lighter rider has to raise his power from 100 watts to 402.5 watts
to catch up--over 300 watts.

A calculator can only approximate how much the actual wind drag and
the real rolling resistance will increase with a heavier bike or
rider, but experience and testing show that heavier riders do indeed
roll downhill faster, given reasonably similar bikes and postures.

To get back to Mark's original question about a 4-lb lighter bike, go
back to the 150 lb riders rolling down the 6% grade at 100 watts.

On a 21 lb bike, the rider hits 32.43 mph.

On a 17 lb bike, the rider hits 32.12 mph, 0.31 mph slower.

To make up that tiny 0.9% speed difference 0.31 mph, the rider on the
4-lb lighter bike needs to raise his power 15%, from 100 watts to 115
watts. That's how important wind drag is when you pedal downhill.

Cheers,

Carl Fogel

It all goes to pot if you've had beans for breakfast.