Bike weight=Rider weight

(PeteCresswell) wrote:
Per :
Recently in another thread, a long-time 220-lb poster mentioned in
good faith that he likes to use 14/15 gauge spokes on the rear, but
15/16 gauge on the front, partly to save weight. The weight saved
amounted to 25 grams, an overall weight reduction of a 0.02311%:

I'm glad to hear that.

Makes me feel a little better about my own riding shoes:

http://tinyurl.com/jffwz

I was expecting something more along the lines of...

http://www.sillyfarm.com/12Costumes/...llow-shoes.jpg

) --- s/b a clown emota-thingy

Bill Sornson wrote:

o) --- s/b a clown emota-thingy

Ooops. )

wrote:
Barnard Frederick wrote:
Penster says...

If I lose 1lb in weight by eating salad and not burgers, is that the same as
spending $$$ on lightweight components to make my bike 1lb lighter?
Mick

Losing rotating weight (wheels, tires, cranks, pedals) is more
important, but other than that, it's about the same.

Calves and feet rotate too! I am actually surprised at how many people
go nuts on lightweight stuff but ride a round in heavy (relatively
speaking in terms of grams per $ compared to other bike components)
shoes.

Joseph

Because pedals, shoes and cranks are counterbalanced (assuming you have
your cranks at 180 deg) does the weight matter????? 100 ft/lbs of
pressure on the pedal puts the same force on the chain whether the
pedals are 100 grams or 454 grams. (or not... please explain if
different or correct)

Shannon

Per Bill Sornson:
I was expecting something more along the lines of...

http://www.sillyfarm.com/12Costumes/...llow-shoes.jpg

That was *very* close to coffee spurting out the nose...
--
PeteCresswell

shannon says...

Because pedals, shoes and cranks are counterbalanced (assuming you have
your cranks at 180 deg) does the weight matter????? 100 ft/lbs of
pressure on the pedal puts the same force on the chain whether the
pedals are 100 grams or 454 grams. (or not... please explain if
different or correct)

Yes, it does matter, but not as much as tires rims and tubes, which
rotate much faster and have a larger rotational diameter.

On 13 Aug 2006 17:56:04 -0700, "shannon"
wrote:


wrote:
Barnard Frederick wrote:
Penster says...

If I lose 1lb in weight by eating salad and not burgers, is that the same as
spending $$$ on lightweight components to make my bike 1lb lighter?
Mick

Losing rotating weight (wheels, tires, cranks, pedals) is more
important, but other than that, it's about the same.

Calves and feet rotate too! I am actually surprised at how many people
go nuts on lightweight stuff but ride a round in heavy (relatively
speaking in terms of grams per $ compared to other bike components)
shoes.

Joseph

Because pedals, shoes and cranks are counterbalanced (assuming you have
your cranks at 180 deg) does the weight matter????? 100 ft/lbs of
pressure on the pedal puts the same force on the chain whether the
pedals are 100 grams or 454 grams. (or not... please explain if
different or correct)

Shannon

Dear Shannon,

The extra mass still has to be accelerated in a circle in order to
apply the pressure to the pedals.

More mass means less acceleration with the same force.

Spin a heavy tire when a car is up on a jack, compare that to spinning
your bicycle's front wheel, and you'll see the difference.

Luckily, the shoes and pedals only whirl at a trivial speed.

At 25 mph with a 2124mm 700c tire, a 52x12 with a 175mm crank turns at
just under 73 rpm, doing a stately 3 mph, while the chain moves at
only 1.8 mph.

So the feet and chain just don't do much accelerating.

On the other hand, the rim, tire, and tube spin at just under 25 mph,
so spinning them up does indeed take more effort.

But you can flip a bike upside down and easily crank the rear wheel up
to that speed with one arm in a couple of seconds (versus two legs
spinning up the front and the rear wheel).

Here's a calculator that lets you fatten your wheels as you please:

http://www.analyticcycling.com/ForcesSource_Page.html

The extra wheel mass slows you slightly uphill, but speeds you up
slightly less downhill.

The extra wheel mass also makes you accelerate slightly more slowly on
the flats, but then helps you coast further and faster--you decelerate
slightly more slowly.)

In real life, of course, bicyclists laboriously build up speed and
then throw most of it away as soon they touch the brake, and uphill
speed advantages outweigh downhill speed advantages because the time
spent going up is much longer than the time spent going back down.

But the shoes and pedals don't spin nearly as fast as the wheels, so
they don't matter nearly as much. A further complication is that your
shoes are attached to a pair of ungainly triple-jointed reciprocating
rods that not only go up and down, but wastefully back and forth.

The powered calves and thighs of a cadaver simply drop and hang
straight down the moment external power is removed--it takes effort to
wave those big chunks of meat and bone around.

We just don't notice the effort because we're used to thrashing our
hindquarters much faster than required by bicycling. A 90 rpm cadence
on the 52x12 described above will produce a steady pedal speed of only
3.7 mph.

That's a modest walking speed, but only as long as we forget that we
must repeatedly whip the trailing foot forward at about 8 mph to
maintain a 4 mph progress.

Cheers,

Carl Fogel