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Discussion Starter · #1 ·
I have an 05 LeMond 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 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. and phyiscally the giant/rider were taller (more frontal area) than myself or the Madone.
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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Windrider (Stubborn)
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Relube.....

your wheel bearings....and try the test again.

In addition........9 lb weight difference will translate into more speed on the downhill. I'm a skinny guy and when I do long downhills with heavier guys I'm always chasing.

finally, technique can make a difference........differences in aero tuck will create gaps.....as will agressive cornering and judicious braking.

Len
 

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Discussion Starter · #3 · (Edited)
Seriously?

it'd make that dramatic a difference?

i haven't touched them since i got them this year aside from snugging up the rear bearings (had some play).
any particular grease?

and we were all in the same basic position as well. a pure bike speed/aero off. no one was signifigantly lower/higher. and certainly not to the effect of 1' every few seconds.

thanks!
 

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Discussion Starter · #5 ·
Bars.

I'm 5cm lower in the bars vs the seat.
and i agree with the statement but all of our rides/weights/bar heights were comparable. and the rider who had the most full frontal was still faster than me.

i could go lower but i'd lose all day comfort for sure.
 

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You go into great deal about the bikes but don't mention what the aero position of each rider was like? That would make a big difference and what a previous poster said about your hubs would be next important, the extra weight will also help to propel a rider on a downhill.

Nothing else is really going to make that much of a difference so trying to make your bike more aero isn't going to change the result in a simple test like that.
 

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Discussion Starter · #7 ·
Aero body position

Sorry if i wasn't clear. we all adopted virtually the exact same aero positioning. Hands on the drops, heads down close to the bars, butt up a bit, knees in tight. again it wasn't a "race" it was a "test" to see any obvious speed differences.
so i didn't go into much detail for the position for that reason.

thanks.
 

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Another item in the mix to consider would be tires and pressure. Some of the higer end tires will roll better with less resistance due to their tire compound, tread and thread count of the casing. This can come at the expense of more money, durability and comfort. But I think that it can certainly be a factor.
 

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Spicy Dumpling
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I still think that position will make a bigger difference than anything in this instance. I can tuck in my elbows and pick up a 1/2 mph on some downhills. How your back is arched, head position, etc can make a bigger difference than tubing on a frame. Next would be wheels etc. You stated you had 46 cm bars, how wide were the other's bars. That could make a big difference as well. Little things add up..
 

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That's the stupidest thing I've heard in a while. If you need to buy something - be it new wheels, or a Cervelo TT frame - just do it. In the mean time, slim down and work on your bike position...or be thankful that you're riding just that tiny bit harder than the other guys, and that your day will come.
 

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Discussion Starter · #13 ·
well that's a perspective i guess.

slim down. well i'm not sure how that'll help me with my aerodynamics, i'm 5' 10" and 164lbs. as are my friends (give or take). Any lighter and i start to reall feel the loss of power. I'm perfectly happy now at this weight for power/fitness.

i am amazingly grateful for being able to ride, and for so many other things. but that too doesn't really impact aerodynamic loss to a large extent.

i don't want to buy a new bike (notice i said i liked my lemond a great deal).
positioning. assume everything rider wise is pretty much equal. and again it wasn't a race, just a test.

my day did come, this past weekend. won my masters A race. And it was on a set of Velomax ascent II carbon tubulars...really won it on a climb then a max effort on the dh side of that climb.

I'm just wondering why guys on similar weight bikes/who are about the same height, and tucked about the same amount can have such a difference in drag/aero ability.

So thanks for saying that my question about aerodynamics was "That's the stupidest thing I've heard in a while" Sdizzle. its appreciated and insightful.
 

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I have an '01 Victoire (so no carbon)...but, most of my riding buddies, who drop me going up the hills, struggle to hang on when I'm going down the hills (even on the flats sometimes)...we're all various shapes and sizes, but mostly I think position on the bike has a lot to do with it (as said above).
 

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Discussion Starter · #15 ·
Remy.

what is the wheelset you have on the 01? i think my former bontrager race lites were faster descenders than what i have now. but now their doing duty on a cross bike.
however i just tightened the rear bearings last week (some lateral play) so maybe i got overzealous.

i'm going to relube and readjust the fulcrums.
then do the test again. and for fun, swap wheels with my friend on the Giant and re-retest (his suggestion).

might be interesting.

this is the bike in its current config.

and with a different bar
 

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Discussion Starter · #16 ·
tires.

i find the conti force/attack to be fast clinchers, i had 110psi in each. can't swear to it but i believe they had similar rubber/pressure. good point though, i'll inquire.

GW1 said:
Another item in the mix to consider would be tires and pressure. Some of the higer end tires will roll better with less resistance due to their tire compound, tread and thread count of the casing. This can come at the expense of more money, durability and comfort. But I think that it can certainly be a factor.
 

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Adorable Furry Hombre
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Before blaming wind resistance & etc.-

I'd blame that [email protected] momentum

<dl><dd>
</dd></dl>The differences here (as well as gravity) would likely matter/offset aerodynamic resistance issues-you said one of the riders/&their rigs wieghed an extra 9lbs?

https://en.wikipedia.org/wiki/Momentum
 

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Discussion Starter · #18 ·
momentum

hmm. yes i said that one guy was heavier. and he was faster than me, but slower than the guy with the madone with race x lite aero wheels.
he did close ground on him after a time though, so the weight issue and momentum makes sense there.
i weigh in the middle i'd suggest between the three of us.


Room 1201 said:
Before blaming wind resistance & etc.-

I'd blame that [email protected] momentum

<dl><dd>
</dd></dl>The differences here (as well as gravity) would likely matter/offset aerodynamic resistance issues-you said one of the riders/&their rigs wieghed an extra 9lbs?

https://en.wikipedia.org/wiki/Momentum
 

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"It's alive!"
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Room 1201 said:
Before blaming wind resistance & etc.-

I'd blame that [email protected] momentum

<dl><dd>
</dd></dl>The differences here (as well as gravity) would likely matter/offset aerodynamic resistance issues-you said one of the riders/&their rigs wieghed an extra 9lbs?

https://en.wikipedia.org/wiki/Momentum
Momentum, yes. Gravity, not really. Remember that gravity does not make heavier objects fall faster than lighter objects. Given the same size, shape and slipperiness, heavier and lighter objects will fall at the same rate of acceleration.

But momentum does seem to carry heavier riders down a hill faster then lighter riders as the heavier riders blast through small resistances which slow down the lighter folk. I've never done an analysis of this effect, but it sure seems to play out in real life.

- FBB
 
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