Wind Tunnel Testing the Al33, XR31T(FSW3), and other alloys

This blog, and series, will be a way more difficult story to tell than I'd thought it would be. 

What we'd expected was that the Zipp 303 reference wheel would be that shade faster at the heavily prevalent and thus more important narrow angles of attack (aka yaw angles), and then extend that lead out into the angles that occur with much less frequency. What actually happened was that the Al33 (our RFSW3 wheelset's rim) and the Kinlin XR31T (that we use in the FSW3) both performed better than the 303 at the most prevalent low yaw angles, starting to cede a bit at around 7.5* and going on from there.


When you do a test like this, you get a lot of data, and it takes a while to chew and digest it. What we present here is just a first, very broad, pass at things. 

The blue vertical bars that you see in the graph are the amount of time the average cyclist is likely to spend encountering each wind angle during a ride. We will offer a very complete explanation of that in the next blog. 

For now, we're just trying to wrap our heads around this, and make good on all the teasing that we've done. Sorry for that, hope it was worth it. 


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Did you remove tare from your wind tunnel results? I’m trying to understand why the shape of the flo30 test differs so much from the results on their website when ya’ll used the same wind tunnel.


So how does a 10mph crosswind compute into angle of attack? Either 90' or a 3/4 headwind. It's been 35 years since college physics and I'm a jr high history teacher now..

Darrell Edwards

Tom – Check my comment on your site – Dave

Dave Kirkpatrick

No worries…I figured a more thorough explanation was coming :-)

Tom Anhalt

I've never rushed any blog out this quickly – if we don't post by 5p it doesn't go to the mailing list, and wanted to hit that. You know that we're going to follow this up with all the details, but this is 30mph at standardized tunnel day. Also remember that your preferred means of seeing this stuff is WAY PAST what most people want and are best served by.

Dave Kirkpatrick

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