How deep of rim does it take to get a noticeable increase in speed due to aerodynamics? Is it the Zipp 303's at 38mm or 404's at 58mm or spinergy ss at 45mm maybe the Hed jet 60mm... I'm talking about the front wheel...
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Re: race wheels [qrguy]
[ In reply to ]
There is no magic threshold. The deeper the better, but rim shape also has an effect. e.g. a 38mm Zipp will exhibit different aerodynamics than a Corima of the same depth.
Generally, you want as deep a rim as you can handle, and that conditions allow. For most, that means a 60mm rim (or a Hed3), but really light riders or very windy areas would be better off with shallower rims.
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Generally, you want as deep a rim as you can handle, and that conditions allow. For most, that means a 60mm rim (or a Hed3), but really light riders or very windy areas would be better off with shallower rims.
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Favourite Swim Sets:
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Re: race wheels [qrguy]
[ In reply to ]
Yeah, no "real" answer. Zipp claims their 303 at 38mm is aero. 404 is 58mm and definitely aero (for real world usage). Reynolds claims their wheels are aero, but only 46mm. TT and Tri peeps usually go for as much as possible (i.e. rear disk, Hed3 up front, 60mm +) since we can't handle a bike anyway :) and weight is really not much of an issue.
I have had Spinergy Rev-Xs, Hed3s, Reynolds and Zipps. By far my favorites are my 404s for an all around wheelset (weight, hubs, aero, looks, but not price). I train on Ksyrium SLs and they feel just as "fast" though. I would actually like to try the Cosmic Carbones.
____________________________________
Fatigue is biochemical, not biomechanical.
- Andrew Coggan, PhD
I have had Spinergy Rev-Xs, Hed3s, Reynolds and Zipps. By far my favorites are my 404s for an all around wheelset (weight, hubs, aero, looks, but not price). I train on Ksyrium SLs and they feel just as "fast" though. I would actually like to try the Cosmic Carbones.
____________________________________
Fatigue is biochemical, not biomechanical.
- Andrew Coggan, PhD
Re: race wheels [qrguy]
[ In reply to ]
Check out the drag numbers on the Hed site. It is interesting that the Jet60 and Jet40 are very similar in drag whereas the Alp (50mm) is much lower than the Jets - probably because of spoke count. Could be they just want to sell more Alps but if does seem that there is more than just rim depth to consider. Zipp also has tons of good tech papers on their site.
I have a Jet60 and am faster with the Spinergy Tilium SS (~45mm) now called the Stealth SS. The Jet60 front has a LOT of spokes, which definitely is not in it's favor. The rule of thumb is to be really "aero" 40+ mm is needed. This has a lot to do with the profile of the rim (curved better than straight sides) and width of rim vs width of tire. Stick a 23mm tire on a 404 or any other rim and the drag goes way up. A 20mm width really needs a 60mm depth to be "aero" in the classic sense, but proportionally speaking a 60mm depth isn't a huge difference from a 45/50mm depth...at least compared to going from a 32 hole Mavic Open Pro. To put it another way, the difference from 45mm to 60mm is likely in the range of 0.1-0.2mph at 20mph at constant wattage. I always recommend the Spinergy or the Alps because I live with huge crosswinds all the time and a 60mm is hard to handle.
