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They're effectively the same. In order to get aero benefit you need rims at least 40mm deep (go to the Zipp website to read about their windtunnel testing and results). So the only difference in your two wheelsets is an equal number of round vs bladed spokes, the difference will be negligible.dagger said:The two I am looking are:

1. 30mm rim depth with 24 round spokes, and

2. 28mm rim depth with 24 bladed spokes.

Which is the the faster of the two? Thanks

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There are way more details in making a wheel faster than just spoke count, rim depth, and spoke profile. You can't "add things up" and get an aswer. Like palewin said, these are effectively the same, and maybe 0.1 to 0.2 mph faster than a standard box section, 32 spoke wheel set.

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Impress your friends and throw both sets off the top of El Capitan or any large cliff. The one that hits the ground first is the more aero.dagger said:The two I am looking are:

1. 30mm rim depth with 24 round spokes, and

2. 28mm rim depth with 24 bladed spokes.

Which is the the faster of the two? Thanks

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11,864 Posts

Don't buy them when you do that, but ask the LBS if you can take them outside so you can see them in daylight, then claim it was all a horrible accident involving a truck, a stepladder and a banana peel.wipeout said:Impress your friends and throw both sets off the top of El Capitan or any large cliff. The one that hits the ground first is the more aero.

Or the heaviest?wipeout said:Impress your friends and throw both sets off the top of El Capitan or any large cliff. The one that hits the ground first is the more aero.

So if I throw off a 400g 16 spoke ZIPP 404 and an old 27" Rigida steel rim on a Maillard threaded freewheel hub and 36 steel spokes weighing ooh about 5 lbs! the more aero wheel will hit first?

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1,348 Posts

Ever heard of sarcasm?dreww said:Or the heaviest?

So if I throw off a 400g 16 spoke ZIPP 404 and an old 27" Rigida steel rim on a Maillard threaded freewheel hub and 36 steel spokes weighing ooh about 5 lbs! the more aero wheel will hit first?

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616 Posts

Uh... actually yes. Two identically shaped objects of differing weight will fall at the same speed. The more aerodynamically shaped object will fall faster regardless of weight.dreww said:Or the heaviest?

So if I throw off a 400g 16 spoke ZIPP 404 and an old 27" Rigida steel rim on a Maillard threaded freewheel hub and 36 steel spokes weighing ooh about 5 lbs! the more aero wheel will hit first?

More sarcasm?BugMan said:Uh... actually yes. Two identically shaped objects of differing weight will fall at the same speed. The more aerodynamically shaped object will fall faster regardless of weight.

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Bugman is trying to confuse us with facts and science. Did you skip that day in physics class?asgelle said:More sarcasm?

Once more slowly.Keeping up with Junior said:Bugman is trying to confuse us with facts and science. Did you skip that day in physics class?

Drag force: F_d = 1/2 Cd A rho V^2 where rho is fluid density, Cd is drag coefficient, A is frontal area, V is fluid velocity. Cd and A both depend on shape

Gravitational Force: F_g = mg where m is mass of body, g is gravitational constant.

At terminal, settling, drift velocity, F_d=F_g: 1/2 Cd A rho V^2 = mg or

V = Sqrt(2 mg / Cd A rho)

So if Cd and A are held constant, velocity goes as the square root of mass. Keep mass constant, velocity will go as the inverse square root of changes in shape as reflected in Cd and/or A. Change Cd, A, and mass and velocity may increase, decrease, or stay the same depending on the particular changes. Now what part of physics class do you think I missed?

Wow - more sarcasm!!asgelle said:So if Cd and A are held constant, velocity goes as the square root of mass. Keep mass constant, velocity will go as the inverse square root of changes in shape as reflected in Cd and/or A. Change Cd, A, and mass and velocity may increase, decrease, or stay the same depending on the particular changes. Now what part of physics class do you think I missed?

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Is it possible to get lactic acid in your brain? My Cliff Notes version of physics is abviously not up to par.asgelle said:...F_d = 1/2 Cd A rho V^2 ...F_g = mg... F_d=F_g: 1/2 Cd A rho V^2 = mg ...V = Sqrt(2 mg / Cd A rho)...

Two identically shaped objects of different weight will fall atBugMan said:Uh... actually yes. Two identically shaped objects of differing weight will fall at the same speed. The more aerodynamically shaped object will fall faster regardless of weight.

A ping pong ball has less aerodynamic drag than a slab of concrete - but the slab of concrete falls faster.

Unfortunately, there is not enough information here to judge. In addition to depth, width and shape (as well as the width of the tire and transition between tire and rim) play important roles.dagger said:The two I am looking are:

1. 30mm rim depth with 24 round spokes, and

2. 28mm rim depth with 24 bladed spokes.

Which is the the faster of the two? Thanks

However, keep in mind that wheels create only about 10% of the total drag, so even if one set of wheels had 30% less drag than another, thats still only about 3% of the total drag.. Even if 3% sounds like a lot, remember that drag power increases with the cube of speed, so a 3% reduction in drag will only produce a 1% increase in speed.

Since these wheels would appear to be fairly similar, the difference in drag is probably inconsequential compared to the total drag, so differences in speed will be nearly immeasurable. There are likely to be other characteristics which will be more important in selecting between these two wheels.

The very best aerowheels can only increase speed by about 2%. At a nomimal 25 mph speed, that's an increase in speed of only about 0.5 mph. And most wheels that claim to be "aerowheels" actually provide only a fraction of the drag reduction of the most aerodynamic wheels possible, so the speed increases with typical "aerowheels" are a small fraction of one mile per hour at best.

Edit: Oh, crap - that was real answer! Sorry guys, I'll put my sarcasm hat back on!

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a semi-aero rim gives you no advantage over a smaller height rim?palewin said:They're effectively the same. In order to get aero benefit you need rims at least 40mm deep (go to the Zipp website to read about their windtunnel testing and results). So the only difference in your two wheelsets is an equal number of round vs bladed spokes, the difference will be negligible.

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