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Discussion Starter · #1 ·
I have an 05 Carbon/ti Victoire, size 57cm, with Fulcrum Racing 3's and Conti force/attack tires. My bar is a 46cm ORA Carbon wing bar. Fantastic bike. Rides amazing. Yesterday a few of us were out for a 100k training ride. Along on the ride was an 06 Giant TCR Advanced (standard factory spec) in size large; and finally a 3yr old Madone (non SL) with race x lite aero wheels. all of our weights were very similar (both bikes and body with the lightest bike being the Giant by a pound or so, but the rider being 10lb more than me at 174lbs.)

I noticed a few times that on longer coasting downhills i was working harder to stay with the other two riders. At one particularly long dh i asked them to do a coast off just to see the differences. It was annoyingly dramatic.
the Madone initially slipped away first, with the Giant close to him. (no one was drafting). I was losing about 1' ever 2 or 3 seconds. After a 2 minute downhill this difference was huge.
I'm assuming this translates directly to increased effort on the flats to maintain speed (of course that's at a certain speed and above for wind drag) but still i can see it being signifigant.

Whats causing this difference? Is the squarer profile of the fulcrums, which look a lot like Mavic Ksyeriums, slower? are the round tubes of the lemond somehow slower than the round tubes of the giant? does the protruding lemond badge cause drag?

Anyone have any suggestions on how i can make my bike slipperier? i love the ride, but for racing i see it as an obvious disadvantage. Do i need a cervelo team instead?

thanks.
 

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Discussion Starter · #3 ·
the swap.

the wheel swap is next, excellent suggestion. i think that may have a big impact (i remember feeling faster going downhill on my race lite wheels....)


daver42 said:
I thought tires play a big factor in creating rolling resistance. What size tires are you running with? Also, if your ride mates are willing, try swapping wheels and repeat your coast test.
 

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for some reason I coast faster than anyone on whatever I ride. I think it has more to do with body mass and gravity than wheels or tires.
 

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WhiskeyNovember said:
Indeed. Don't underestimate the extra 10 pounds on the other rider...
or even 5lbs. A teammate and I who are about 5 lbs apart did the same sort of thing, going so far as to swap bikes and such, and in the end, the heavier of us (him) always out-coasted me downhill, not by much on short hills, but by a farely significant margin on longer descents. with me (ligher) on a heavier bike things were closer, but he still weighed more overall and still won.

I'm ok with it however, as i can out-climb him. play up the stregnths of being lighter.....you said you were 164? you can out-descend all of us skinny guys, so enjoy it.

edit - i ride a lemond, my friend doesn't. when he was on my lemond and i was on his bike (orbea) he still smoked me, so id say there isnt really a "disadvantage" to lemond aero qualities, in fact, on my alu lemond (tourmalet) with all the butted/shaped tubing and such, the frame looks as if it would be rather aero.
 

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not to knock your efforts, but that isn't a very scientific way to figure out why you are coasting slower than your buddies. I'd look at small things too like making sure your hubs are in good shape, you are all running proper psi, etc.

While servicing my rig yesterday, I found my rear hub to be wayy overtightened (Ksyrium SSC), I adjusted it and it rolls a little bit better, which would definately give me another 1 inch every 2-3 secs ;)
 

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Sluggo
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Gravity and body mass

WhiskeyNovember said:
Indeed. Don't underestimate the extra 10 pounds on the other rider...
I barely made it out of high school, so I'm not an authority about this. But it seems you're saying any extra weight a rider may be carrying will help him on the downhill because of gravity. Therefore a two hundred pound rider will descend faster than, say, a one hundred pound rider. Galileo disproved that theory back in the day when he rolled balls of different masses on incline planes. His experiment proved that falling or rolling objects (rolling is a slower version of falling, as long as the distribution of mass in the objects is the same) are accelerated independently of their mass. He also concluded that objects retain their velocity unless a force – often friction – acts upon them, refuting the accepted Aristotelian hypothesis that objects "naturally" slow down and stop unless a force acts upon them.
In other words, brake rub may be slowing the OP down. Or a tight hub.
BTW, I've got an '04 Victoire. Sucker flies. If anything slow about it, it's the engine.
 

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Galileo didn't operate in a vaccuum

Jaxattax said:
I barely made it out of high school, so I'm not an authority about this. But it seems you're saying any extra weight a rider may be carrying will help him on the downhill because of gravity. Therefore a two hundred pound rider will descend faster than, say, a one hundred pound rider. Galileo disproved that theory back in the day when he rolled balls of different masses on incline planes. His experiment proved that falling or rolling objects (rolling is a slower version of falling, as long as the distribution of mass in the objects is the same) are accelerated independently of their mass. He also concluded that objects retain their velocity unless a force – often friction – acts upon them, refuting the accepted Aristotelian hypothesis that objects "naturally" slow down and stop unless a force acts upon them.
A couple of things -
Firstly, although this story is often told, Galileo never performed an experiment by dropping objects from the Tower of Pisa.

Secondly, two object only fall at the same rate in a vaccuum. When air drag is added to the equation, different results may be obtained.

So let me ask this: Which weighs more - a skydiver with his parachute packed tightly into its pack; or the same skydiver with his parachute deployed? The skydiver with his parachute weighs exactly same whether the parachute is deployed or not, of course. So, does the skydiver fall at the same rate whether or not the parachute is deployed? Of course not - even though the force of gravity is the same, there is more air drag force when the parachute is open, so the skydiver with the open parachute falls at a slower rate.

Next question: Say a 200 lb. skydiver uses exactly the same type of parachute as a 150 lb. skydiver - when both have their parachutes deployed, which one falls faster? The heavier skydiver, of course - although both skydivers have the same air drag caused the parachute, the heavier skydiver has a higher gravity force. Because the net force is higher, the heavier parachuter falls faster.

Final question: Two cyclists are descending a hill. Both have the same bicycles, both are in equally tight tucks so they have the same aerodynamic drag force, but one cyclist weighs more than the other - which cyclist descends faster?
 

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Sluggo
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Mark McM said:
A couple of things -
Firstly, although this story is often told, Galileo never performed an experiment by dropping objects from the Tower of Pisa.

Secondly, two object only fall at the same rate in a vaccuum. When air drag is added to the equation, different results may be obtained.

So let me ask this: Which weighs more - a skydiver with his parachute packed tightly into its pack; or the same skydiver with his parachute deployed? The skydiver with his parachute weighs exactly same whether the parachute is deployed or not, of course. So, does the skydiver fall at the same rate whether or not the parachute is deployed? Of course not - even though the force of gravity is the same, there is more air drag force when the parachute is open, so the skydiver with the open parachute falls at a slower rate.

Next question: Say a 200 lb. skydiver uses exactly the same type of parachute as a 150 lb. skydiver - when both have their parachutes deployed, which one falls faster? The heavier skydiver, of course - although both skydivers have the same air drag caused the parachute, the heavier skydiver has a higher gravity force. Because the net force is higher, the heavier parachuter falls faster.

Final question: Two cyclists are descending a hill. Both have the same bicycles, both are in equally tight tucks so they have the same aerodynamic drag force, but one cyclist weighs more than the other - which cyclist descends faster?
To your first point, my post says nothing about Galileo and the Leaning Tower of Pisa. My post said that Galileo performed experiments on balls of different mass on inclines. The conclusion that he drew from those experiments was that gravity has equal pull on all objects.
Regarding your other points and questions, I'm not going to pretend that I'm smart enough about physics and mechanics to post a response here. Instead, I'll refer you to a site that, among other things, demonstrates that falling objects, and balls rolling down an incline, tend to accelerate at a constant rate. Here you go....http://www-spof.gsfc.nasa.gov/stargaze/Lfall.htm
 

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Jaxattax said:
To your first point, my post says nothing about Galileo and the Leaning Tower of Pisa. My post said that Galileo performed experiments on balls of different mass on inclines. The conclusion that he drew from those experiments was that gravity has equal pull on all objects.
Regarding your other points and questions, I'm not going to pretend that I'm smart enough about physics and mechanics to post a response here. Instead, I'll refer you to a site that, among other things, demonstrates that falling objects, and balls rolling down an incline, tend to accelerate at a constant rate. Here you go....http://www-spof.gsfc.nasa.gov/stargaze/Lfall.htm

You can find anything on the internet!!! :mad2:
 

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Discussion Starter · #14 ·
too tight?

interesting post; i HAD tightened the rear hub (it had lateral movement) but i think it may have been too tight after that. i backed it of 1/4 turn and it still had no lateral play but felt looser when spinning. did a solo ride last night and it felt great, need the coast off again to confirm.

Peith said:
not to knock your efforts, but that isn't a very scientific way to figure out why you are coasting slower than your buddies. I'd look at small things too like making sure your hubs are in good shape, you are all running proper psi, etc.

While servicing my rig yesterday, I found my rear hub to be wayy overtightened (Ksyrium SSC), I adjusted it and it rolls a little bit better, which would definately give me another 1 inch every 2-3 secs ;)
 

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Discussion Starter · #15 ·
Lessons Learned: Don't overtighten your wheels then complain about coasting speed.

Yup. my bad. overtightened the rear wheel on the fulcrums. didn't seem like it was too tight but backing it off and ensuring it didn't have any play...sped the whole shebang up.

thanks for the input though, all sensible for the most part (cept for the guy with the bad attitude...).

cheers.
 
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