How deep to be aero?

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2009-09-15 6:52 AM

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Subject: How deep to be aero?

At what depth of wheel does a wheel start to give an aero benefit?

The wheels I was looking at are 31mm deep, would there be an aero benefit at this depth? If not at what depth would you say you start to get aero benefit?

2009-09-15 7:03 AM
in reply to: #2406643

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Subject: RE: How deep to be aero?
I've always heard 50mm, but can't come up with a solid source that substantiates that at the moment...
2009-09-15 7:19 AM
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Subject: RE: How deep to be aero?
I would assume (perhaps incorrectly) that this would also be based on speed.
2009-09-15 7:48 AM
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Subject: RE: How deep to be aero?
To make matters even worse, I've heard that different aero wheels have different degrees of drag based on what crosswind component you have.  It's a very complex equation.
2009-09-15 7:50 AM
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Subject: RE: How deep to be aero?

Science is such a pain!

Do you think there might be an aero benefit at 31mm if you had to guess or do they just look better than standard wheels that come with cheap bikes?

2009-09-15 8:23 AM
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Subject: ...
This user's post has been ignored.

Edited by JeepFleeb 2009-09-15 8:24 AM

2009-09-15 8:54 AM
in reply to: #2406643

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Subject: RE: How deep to be aero?
The general rule is that you need a 3:1 aspect ratio in order to get a decent aero benefit; since a typical racing tire is going to be in the 19-23mm range then you are looking at a rim depth of 38-46mm in order to achieve this (assuming a perfectly circular tire profile).

ETA - is this going to be a training or race wheelset?

Shane

Edited by gsmacleod 2009-09-15 8:57 AM
2009-09-15 9:30 AM
in reply to: #2406906

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Subject: RE: How deep to be aero?
I do not doubt your suggestion of 3:1.  Just trying to understand how 19-23 and 38-46 is not a 2:1 ratio.

I would think that 3:1 would be 57-69 depth on the wheel.

Perhaps a 19-23 mm tire is the circumference and you are looking at the diameter?  but then we have to include the width of the rim into the calculation?

Edited by kesslergk 2009-09-15 9:32 AM
2009-09-15 9:31 AM
in reply to: #2406906

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Subject: RE: How deep to be aero?
gsmacleod - 2009-09-15 2:54 PM The general rule is that you need a 3:1 aspect ratio in order to get a decent aero benefit; since a typical racing tire is going to be in the 19-23mm range then you are looking at a rim depth of 38-46mm in order to achieve this (assuming a perfectly circular tire profile).

ETA - is this going to be a training or race wheelset?

Shane


To be honest they will probably be both.
2009-09-15 9:39 AM
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Subject: RE: How deep to be aero?

kesslergk - 2009-09-15 10:30 AM I do not doubt your suggestion of 3:1.  Just trying to understand how 19-23 and 38-46 is not a 2:1 ratio.

3:1 is tire + rim. You forgot to add back in the size of the tire.

2009-09-15 9:41 AM
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Subject: RE: How deep to be aero?
Ah yes.  Thanks for that.

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