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So why do we still see professionals using box section rims in road races ?
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Originally Posted by Homebrew01
(Post 10271720)
So why do we still see professionals using box section rims in road races ?
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Originally Posted by Homebrew01
(Post 10271720)
So why do we still see professionals using box section rims in road races ?
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Originally Posted by f4rrest
(Post 10230969)
The modeling here demonstrates that aero is much more important than wheel weight, even riding uphill at 17mph.
http://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.
Originally Posted by urbanknight
(Post 10271681)
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. |
Originally Posted by kudude
(Post 10271896)
do what now?
Originally Posted by kudude
(Post 10271896)
I wish the frog thing was true, but sadly http://www.snopes.com/critters/wild/frogboil.asp
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Originally Posted by urbanknight
(Post 10271923)
+1 The only "hill" I can climb at 17 mph is a 1% grade.
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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. |
Originally Posted by umd
(Post 10272009)
Recent training has shown me that I can climb up a 6% grade at about 14mph (or a 5% at 15mph) at VO2max power :p
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Originally Posted by goodtimes5
(Post 10271569)
So what kind of rim height are we talking about where aero advantages are easily discernible?
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Originally Posted by goodtimes5
(Post 10271569)
So what kind of rim height are we talking about where aero advantages are easily discernible?
The data in the graph is from this test - rim depth versus power absorbed at 50 km/h (lower is better!). http://img82.imageshack.us/img82/6635/wheelaero6.jpg 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. |
It should be noted in bold print that this chart assumes 50 km/hr (or 30 miles per hour). It would look dramatically different for most normal speeds including the speed that the original poster usually rides.
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Originally Posted by fatallightning
(Post 10271863)
outside of cobbled classics, you very rarely do. the change from say, '01 to now is dramatic. and the trend looks to go as deep as you can handle.
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Originally Posted by roshea
(Post 10272415)
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!). http://img82.imageshack.us/img82/6635/wheelaero6.jpg 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? |
Originally Posted by f4rrest
(Post 10272086)
Oh, and umd, 14mph at 6% is darned good.
Originally Posted by urbanknight
(Post 10272199)
Well, that explains why I got dropped at the first real climb at Poor College Kids RR last year.
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Originally Posted by jrobe
(Post 10272453)
It should be noted in bold print that this chart assumes 50 km/hr (or 30 miles per hour). It would look dramatically different for most normal speeds including the speed that the original poster usually rides.
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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) :D
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Originally Posted by asgelle
(Post 10272773)
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?
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. |
Originally Posted by jrobe
(Post 10273226)
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. |
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