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53x12
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by 53x12 on Sat Aug 23, 2014 2:13 pm
ghisallo2003 wrote:For completeness, and to understand the interplay of variables, I would like to see the old wheels used as the reference set also.
Why?
"Marginal gains are the only gains when all that's left to gain is in the margins."
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mjduct
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by mjduct on Sat Aug 23, 2014 4:07 pm
Thanks for proving my point, weight is easily 75% of that pie, and the rims have a proportionally huge effect in proportion to their tiny percentage of bike/ rider mass...
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ghisallo2003
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by ghisallo2003 on Sat Aug 23, 2014 4:22 pm
53x12 wrote:ghisallo2003 wrote:For completeness, and to understand the interplay of variables, I would like to see the old wheels used as the reference set also.
Why?
Because I would like to understand the extent to which it is the design of the aero frames to work in combination with deep section wheels that is effective or is it a stand-alone effect. For example, is the time saving per 40km the same with all wheel types?
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53x12
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by 53x12 on Sat Aug 23, 2014 4:33 pm
mjduct, did you read the full article?
In fact, in most cases, wheel mass and rotational inertia tend to be exceedingly small determinants of a particular wheel's performance; much less than the effects of the wheel's aerodynamics, or a particular tire's rolling resistance.
In the example I show below, you'll hopefully begin to see why these sorts of rankings of inertia are actually concentrating on a wheel property that has only a minor affect on wheel performance in the context of the overall bike+rider "system."
Additionally, the increases in aero drag and rolling resistance accounted for approximately 1/3 of of the total increase in peak pedal force. The effect of increasing the rim mass of the wheels by nearly a full pound (400g) resulted in an increase in the average peak pedal force over the 5s acceleration of just 1%…in other words, an amount not likely to be "felt" at the pedals. It's pretty clear which areas of wheel performance the most benefit can be gained from making improvements: in the aerodynamics of the wheels and the rolling resistance of the tires and tubes applied to them.
"Marginal gains are the only gains when all that's left to gain is in the margins."
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kbbpll
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by kbbpll on Sat Aug 23, 2014 4:54 pm
I disagree. It was a great comparison.
I agree that it's interesting to see them actually do it, but I'm not sure how useful the question "small diameter steel vs modern aero carbon frame" is. What seems more useful is "how much have we really gained in the current aero fad versus the aero fad from the 1980s", and from that standpoint I'd really like to see the results versus that Panasonic or Cinelli. The '80 Dura-Ace AX group claimed 20% drag reduction at the time, via "the use of the bicycle industry’s first wind tunnel".
Basically the test is saying roughly 1 minute faster over an hour of racing, which is 1.7%. Seems like one of the early 80s "aero" bikes could easily be 1.7% better than it's contemporary round steel in a similar test, and could end up pretty close to the Venge.
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Geoff
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by Geoff on Sat Aug 23, 2014 6:05 pm
I guess the obvious difference between the bikes we raced in the 80s and today is the materials. My McLaren Venge is pretty light and really stiff, and my S5 is no noodle, either. That is a far cry from the bikes ofthe 80s.
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dunbar42
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by dunbar42 on Sun Aug 24, 2014 4:12 am
59 seconds over 40k sounds about right for the Venge based on the Felt AR white paper. That equates to about 15 watt savings at 30mph which scales down to ~11 watts at 25mph. The funny thing is Specialized is only claiming the Venge frame saves 45 seconds over 40k compared to the Tarmac which is only a 10 watt savings at 30mph.
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kbbpll
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by kbbpll on Sun Aug 24, 2014 5:59 am
^^ So, an "aero" frame saves 59s over 40km in that test (versus what?), but the Venge saves 50s over 40km versus an 80s round steel frame? Sounds like an 80s frame beats whatever it was by 9s.
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HillRPete
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by HillRPete on Sun Aug 24, 2014 11:26 am
Have to come back to the Venge vs. Round Steel test.
It is known that a bottle on the down tube improves aerodynamics
http://www.slowtwitch.com/mainheadings/ ... ttles.htmlWhat I'm wondering is, what would happen when the Venge vs Round Steel would be repeated with a bottle. Would the benefits of the bottle just add up in both cases? I kinda doubt it, if the Venge (or any other frame) was designed and optimised without the bottle in mind.
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53x12
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by 53x12 on Sun Aug 24, 2014 2:17 pm
"Biggest difference in drag comes from the position of the rider. Do they test those bikes with a rider in the exact same position?"
Did you try opening the video and watching it yet? It was provided for a reason.
"Marginal gains are the only gains when all that's left to gain is in the margins."