Open Pro Aerodynamics
 

We've all seen this chart:

http://accel10.mettre-put-idata.over...ro_english.jpg

In the R-Sys thread, one of the posts mentioned that it would have been nice if the Open Pro had been included as a control data point. I was wondering about the aerodynamics of the Open Pro, since I own a couple sets myself.

Does anybody know where a 32 spoke Open Pro front wheel would fall on this chart?

The A-Class ALX440SL might be close, I don't really know though.

ALX440SL rim profile:
http://www.aclass-wheels.com/images/draw/alx440sl.gif

Whole wheel:
http://www.aclass-wheels.com/images/products/ALX440.jpg

The rim shapes seem very close. But the OP is asking about 32 spoke wheels. Assuming standard lacing, the regular 32 Open Pro would be less aero.

yeah, and the OP32 doesn't use bladed spokes either.

My real question is whether it would be less aero than the much loved/hated Ksryium SL. (This is for my poor-man's TT machine -- I have a wheel cover for the rear and was wondering what to do about the front.)

im more curious about the 30mm kinlin rims with some cx ray spokes.

They would be a little less aero than the Ksyriums, because those use bladed spokes and fewer of them. The biggest downside to the standard Open Pro setup over similar rims is probably weight. But they wouldn't be so aero either. On that chart, I might put them near the Aksiums.

You're concerned about the aerodynamics of Open Pro's? Me thinks you're worrying about the wrong thing.

+1

Ummm...those bladed spokes on a Ksyrium wheel are huge. They have to be since they're made out of aluminum. I'm positive they are LESS aerodynamic than a typical gage round spoke. In fact, I recall seeing a drag plot somewhere that showed a K wheel having more drag than a low-profile, 32 spoke wheel...now where is that...?

My original thought was to see how "regular" box section rims score as a basic rim for control or base-line, so that all the other rims could be relative to that.

Yeah that graph should have a 32h OP rim as a control. Zipp, Hed and other companies list a 32h rim as their baseline

Are they ever going to do another "Great Wheel Test" with more current wheels? I would like to see some new numbers.

I'm concerned because I have the choice of an Open Pro or a Ksryium as the front wheel of a tri/tt rig. I have a rear wheel cover but didn't want to shell out any more money for a front wheel if I could avoid it.

Ksryium.

+1

You'll pry my Open Pros from my skewers when I'm cold in the grave ... but aero they ain't.

http://forums.roadbikereview.com/att...1&d=1141267293
Data above from Zipp. For reference to your chart, the "20 flat AL spoke" wheel is a Ksyrium SL. A GL330 is a true box rim, so a few mm shallower than an Open Pro but not much. Spokes are round 14/15, hub Record.

http://forums.roadbikereview.com/att...1&d=1141267332
Data above from Tour magazine. An MA rim is (IIRC) b/w a GL330 and an Open Pro in depth. Dunno spokes used on test wheel.

Actually, a lot of factory type wheels have deeper rims so as to allow the use of fewer spokes. This nullifies much of the weight advantage those wheels might have from losing some spokes. Open Pros are one of the lighter clincher rims on the market.

Curveship: That's perfect and confirms my feelings about the wheels: that neither is particularly aero but the Ksryiums are a bit more so.

Shoot, looks like those charts didn't post. I've attached them, Zipp data first then Tour.

That isn't quite the way it is. The advantage of deeper rims is they are more aero. Becuase deeper rims are stronger, they don't need as many spokes. That also allows them to be more aero as well but the deep aero shape of the rims is the chief benefit.

While lighter rims might feel nice, they offer little in the way of performance improvements. Weight gives a very slight edge in climbing but that's about it.

You're thinking about it wrong. The object of the question was to come up with a reality check and the ubiquitous OP is a great 'baseline'.

I'm (just) curious about my Rolf Elans and my DV46's. Neither of my wheelsets is listed.

Any know of any new data points?

I agree, but my post was a response to Aicabsolut who said "The biggest downside to the standard Open Pro setup over similar rims is probably weight." which is incorrect atmo :)