burnthesheep

no mountains for that thing.....but I have done neighborhood rides on it at about 85ft/mi at 20mph+ before. My double setup is a 56/42. 42/30 is more than enough for most hills here. 56 means I can do 95rpm downhill at a solid speed.

Koyote

Sure. But compare those Merckx team frames to other steel frames of the era...

Random11

I'm no physicist, but... a body in motion tends to stay in motion, so once up to speed, and on level ground, you're pedaling just to overcome the rolling resistance of the bike plus the air resistance. The weight of the bike (and rider) is irrelevant.

downhillmaster

Break on through to the other side.

asgelle

you may want to look a little harder at rolling resistance.

cjenrick

try riding an old track bike with chrome handlebars and stem and steel cranks. when you get on it from a dead stop that darn thing moves,

theory is ok, experiments are better, if you like to climb out of the saddle, then a stiffer frame is going to be an advantage.
been there with the vitus on old la honda road, moody road to skyline, rather have a steel frame or those hills,

phyisics? i was alright, was better at calculus,

79pmooney

Are the fits identical? If not, and the ti bike is indeed faster, you now have real info on what works for your body. Think about it. Bike weight differences matter to the tune of the bike's weight plus your weight. 2 pounds of bike weight is 2 pounds in what? say 190 pounds of you and bike or barely over 1%. But slightly different position on the bikes? That could be like slightly tweaking the stroke on a race car engine and the difference could be a lot more. There could also be an aero difference if the two bikes have different levels of comfort..

cjenrick

another benefit of a stiffer frame is you can launch an attack on a steep climb without false shifting.

with the vitus carbone, there was no way i could climb out of the saddle on redwood gulch rd where it is 18 percent i had to use a smooth pedal stroke to keep from dogging down into a bigger gear. if someone goes by you have to let him go til you reach hwy 9. then you could put the hurt on them with the weight savings.

i saw a guy enter the cats hill criterium on a vitus, and i am thinkin to myself, good luck buddy, i did not see him cross the finish line.

so i avoiding mis-shifts can be considered faster, then a heavier frame can sure be faster.

Random11

Enlighten me as to what I'm missing...

wphamilton

He's surely referring to the basic equation for rolling resistance, which is proportional to weight.

On topic I think there is a specific case where the heavier bike - other things equal - may be faster on a closed loop course. It might be too much a can of worms to go into here though.

Difficultocelot

Everything equal a heavier bike would be faster on downhill, but slower uphill and flat since there is more mass to move. if things weren't equal, it would depend on rolling resistance, drag, and other factors.

wphamilton

Speed will also depend on the angular momentum of the wheels which complicates your otherwise correct description.

Random11

Is this true? Gravity certainly assists when going downhill, but doesn't gravity have the same effect on objects regardless of their weight? Gravity accelerates falling bodies at 9.8 meters per second per second regardless of their weight (in the absence of air resistance). Is this any different for a bicycle rolling downhill? Wouldn't gravity have the same effect on lighter bikes as heavier bikes?

asgelle

What are the units of acceleration? How about force?

urbanknight

A bike is only as fast (or slow) as the rider on it.

Koyote

This assumes that you are maintaining a perfectly constant speed...Which is impossible. Even a ride such as the one you describe is a series frequent deccelerations and accelerations. It happens due to your pedal stroke, shifting, drinking, the wind, changes in posture, tiny changes in terrain and grade, etc etc etc.

tl;dr: you have hypothesized a ride that has never happened in the history of bicycles.

urbanknight

Actually, that pretty much described a velodrome time trial.

Koyote

That occurred to me… But I suspect that, even then, the speed is not perfectly constant.

tomato coupe

Bikes don't operate in the absence of air resistance.

asgelle

But the gravitational force is the same in vacuum or through a medium.

tomato coupe

Yes, but the gravitational force on a heavy bike is greater than the gravitational force on a light bike. A heavy bike and a light bike accelerate under gravity at the same rate initially, but they (usually) start to deviate once the speed is high enough that air resistance comes into play.

HTupolev

If a bicycle is heavier but otherwise identical, then the force and power that it receives from gravity while going downhill is greater relative to its aerodynamic drag. So for a given steady downhill effort, a rider will be able to sustain slightly higher speeds. It's similar to the issue of terminal velocity for objects falling in atmosphere.

Yes, although a heavy bike should theoretically reduce the magnitude of the microaccelerations.

urbanknight

Of course no ride would be PERFECTLY constant, but the question is if it is constant ENOUGH to make weight negligible. I know that time trial setups often favor aerodynamics over light weight, but yeah I guess the added weight itself wouldn't be considered an advantage.

Trakhak

Czech pro rider Oskar Sosenka set a new world hour record in 2005 using a 3.2-kg rear wheel. The complete bike weighed 9.8 kg.

Cyclist0108

There are known knowns, known unknowns, unknown unknowns, and Donald Rumsfeld.