Lightweight versus aero-a different question
01-14-10 | 10:44 PM
#26
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So why do we still see professionals using box section rims in road races ?
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01-14-10 | 10:46 PM
#27
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01-14-10 | 11:40 PM
#28
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01-14-10 | 11:54 PM
#29
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The modeling here demonstrates that aero is much more important than wheel weight, even riding uphill at 17mph.
https://www.biketechreview.com/archive/wheel_theory.htm
There are some other articles on that site that show lightweight wheels start to make sense when the hill is really steep (around 15% gradient), but it depends somewhat on how fast you can travel uphill as well.
https://www.biketechreview.com/archive/wheel_theory.htm
There are some other articles on that site that show lightweight wheels start to make sense when the hill is really steep (around 15% gradient), but it depends somewhat on how fast you can travel uphill as well.
You just opened Pandora's box. It seems that most people claim 42mm, but I'm pretty sure than came from an advertisement from a company that makes 42 or 43mm deep rims. I have a feeling that it's a sliding scale, like bringing a frog in water to a slow boil. You also have to realize that the depth of the rim is not the only determining factor either.
I stopped worrying about it. I bought some 19mm deep rims for my next build. Why? Because I want to tell people I have a sub 1400g set of wheels (just so I can), and even a 100mm deep rim wouldn't make my slow @$$ win any races anyway.
I stopped worrying about it. I bought some 19mm deep rims for my next build. Why? Because I want to tell people I have a sub 1400g set of wheels (just so I can), and even a 100mm deep rim wouldn't make my slow @$$ win any races anyway.
01-15-10 | 12:07 AM
#30
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+1 The only "hill" I can climb at 17 mph is a 1% grade.
Yeah, but I'm sure the point got across.
I wish the frog thing was true, but sadly https://www.snopes.com/critters/wild/frogboil.asp
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01-15-10 | 12:43 AM
#31
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01-15-10 | 01:39 AM
#32
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Nevermind the messed up paraphrasing in my post, the takeaway is that aero trumped weight in the model even at much steeper grades (not going 17mph either, lol).
Oh, and umd, 14mph at 6% is darned good.
Oh, and umd, 14mph at 6% is darned good.
01-15-10 | 03:31 AM
#33
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01-15-10 | 05:24 AM
#34
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01-15-10 | 07:04 AM
#35
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The data in the graph is from this test - rim depth versus power absorbed at 50 km/h (lower is better!).
Basically, it's not linear and it's not simple. Rim depth is only part of the equation - the shape of the rim and the number and shape of spokes also matter. A "good" wheel with a 20 mm rim can do better than a "bad" 45 mm rim, but that sort of outcome is rare. Things start to improve at 30 mm and are considerably better over 50 mm.
01-15-10 | 07:24 AM
#37
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Since the top pros can get super light AND aero rims and if a dog gets in their way and the wheel gets tacoed, a replacement is just moments away.
01-15-10 | 07:28 AM
#38
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I've said it before, and I'll say it again:
The data in the graph is from this test - rim depth versus power absorbed at 50 km/h (lower is better!).
Basically, it's not linear and it's not simple. Rim depth is only part of the equation - the shape of the rim and the number and shape of spokes also matter. A "good" wheel with a 20 mm rim can do better than a "bad" 45 mm rim, but that sort of outcome is rare. Things start to improve at 30 mm and are considerably better over 50 mm.
The data in the graph is from this test - rim depth versus power absorbed at 50 km/h (lower is better!).
Basically, it's not linear and it's not simple. Rim depth is only part of the equation - the shape of the rim and the number and shape of spokes also matter. A "good" wheel with a 20 mm rim can do better than a "bad" 45 mm rim, but that sort of outcome is rare. Things start to improve at 30 mm and are considerably better over 50 mm.
What is the cost of this 10 watt reduction in power needed to maintain 30mph?
01-15-10 | 09:18 AM
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01-15-10 | 09:21 AM
#40
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Again hard words. What does dramatically different mean? The y-axis would be shifted to lower values at slower speeds, but other than that, what changes would you expect to see?
01-15-10 | 09:35 AM
#41
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Also it's worth noting that 10 watts while not a lot in absolute terms could be the difference between being over threshold or not. The body's ability to produce and sustain power is not linear and when you are at the edge of your threshold any savings you can manage is beneficial. Also it looks like 20mm rims are closer to 30W and 60mm rims are getting down to 15W so you can save even more. As to the cost, that's east enough to figure out. 15W = $CostOf(60mm) - $CostOf(20mm) 
01-15-10 | 11:25 AM
#42
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From this chart, you could conclude about a 10 watt advantage at 30 mph going from a 20mm rim to a 60mm rim. I would guess that the advantage under 20 mph would be under half of this (or < 5 watts).
The original poster states that he does primarily solo training rides (and frequently gets dropped on group rides). I don't know what his typical riding speed is but I bet it is under 20 mph. In other words, he has to spend megabucks to gain about a 3-5 watt advantage.
He would in all liklihood, benefit far greater from a better training system (maybe a power based system) than from very expensive wheels.
01-15-10 | 11:02 PM
#43
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From this chart, you could conclude about a 10 watt advantage at 30 mph going from a 20mm rim to a 60mm rim. I would guess that the advantage under 20 mph would be under half of this (or < 5 watts).
The original poster states that he does primarily solo training rides (and frequently gets dropped on group rides). I don't know what his typical riding speed is but I bet it is under 20 mph. In other words, he has to spend megabucks to gain about a 3-5 watt advantage.
He would in all liklihood, benefit far greater from a better training system (maybe a power based system) than from very expensive wheels.
The original poster states that he does primarily solo training rides (and frequently gets dropped on group rides). I don't know what his typical riding speed is but I bet it is under 20 mph. In other words, he has to spend megabucks to gain about a 3-5 watt advantage.
He would in all liklihood, benefit far greater from a better training system (maybe a power based system) than from very expensive wheels.
