Can anybody hazard a guess as to what sort of aero benefit bladed spokes have compared to round spokes. To be more specific, I have a set of Zipp 404s that were built using round spokes for greater strength/durability, and was wondering if they would be significantly more aerodynamic if they were rebuilt with bladed spokes. The wheels are used for both training and racing, so strength/durability is a consideration. I am most interested in the front wheel since I have been considering getting a wheel cover for racing in which case the spokes will not matter. I am guessing around a few seconds per 40 km.
I would take a Sapim blade over any round spoke from any MFG. Some of the other bladed spokes out there are more fragile (Wheelsmith and DT for instance) and you do better off with those MFG’s with “ovals”. There is really no reason to go double butt or even taper style Revolution or Super Comp unless you are counting grams as they are slightly less weight than a Sapim - but again, not as strong (IMO) as the Sapim.
If I were to rebuild the wheels it would be with Sapim CX-Ray spokes. My primary concern is aerodynamics. Do you believe the Sapim CX-Ray spokes will offer a noticeable aero benefit over round spokes?
If I were to rebuild the wheels it would be with Sapim CX-Ray spokes. My primary concern is aerodynamics. Do you believe the Sapim CX-Ray spokes will offer a noticeable aero benefit over round spokes?
no it will not be noticeable
but it will be there
i remember john cobb posting that round and bladed spokes tested similarly.
it would probably take less energy to spin a wheel with bladed/ovalized spokes.
i dont think ist worth rebuilding a wheel just for aero spokes. i would never consider redoing the rear wheel since its likely to be covered by a wheel cover.
And it will look cool…
If we are only talking a few seconds/40 km at best, then I don’t see the point in rebuilding a perfectly good wheelset.
And it will look cool…
If we are only talking a few seconds/40 km at best, then I don’t see the point in rebuilding a perfectly good wheelset.
I would agree.
Agreed, I’d choose the bladed CX-rays if starting from scratch, but the gain is not enough to warrant a re-build if there’s nothing wrong w/ the rim or hub, too.
Some data from Damon Rinard’s old website…a bit hard to interpret due to different hubs, but hey, don’t shoot the messenger :
Bicycle wheel drag - lbs at 30 mph
Yaw Angle (degrees)
Wheel 0 5 15 Ave.
Mavic 3G 700C 0.220 0.183 0.147 0.183
Mavic flat disk 700C 0.170 0.161 0.126 0.152
Sun M19AII 700C, 28 round 15g spokes, Shimano hub 0.165 0.178 0.207 0.183
Sun M19AII 700C, 18 round 15g spokes, Shimano hub 0.156 0.174 0.198 0.176
Sun Buzz 700C, 12 round 16g spokes, Shimano hub 0.139 0.150 0.174 0.154
Sun Buzz 700C, 12 round 15g spokes, Shimano hub 0.145 0.141 0.163 0.150
Sun Buzz 700C, 18 bladed spokes, Hugi hub 0.136 0.148 0.156 0.147
Sun Buzz 700C, 24 bladed spokes, Hugi hub 0.136 0.158 0.183 0.159
Sun Venus 700C, 10 round 15g spokes, Shimano hub 0.145 0.150 0.170 0.155
Sun Venus 700C, 12 round 15g spokes, Shimano hub 0.126 0.152 0.198 0.159
Sun Venus 700C, 18 round 15g spokes, Shimano hub 0.132 0.154 0.205 0.164
Sun Venus 700C, 24 round 15g spokes, Shimano hub 0.158 0.178 0.196 0.177
Mavic 3G 650C 0.198 0.174 0.158 0.177
Mavic flat disk 650C 0.158 0.152 0.106 0.139
Sun M19AII 650C, 24 round 15g spokes, Shimano hub 0.139 0.172 0.203 0.171
Sun M19AII 650C, 10 round 15g spokes, Shimano hub 0.141 0.158 0.189 0.163
Sun Buzz 650C, 10 round 16g spokes, Shimano hub 0.130 0.121 0.145 0.132
Sun Buzz 650C, 10 round 15g spokes, Shimano hub 0.148 0.145 0.172 0.155
Sun Buzz 650C, 18 bladed spokes, Campy hub 0.119 0.119 0.136 0.125
Sun Buzz 650C, 18 bladed spokes, Hugi hub 0.128 0.136 0.152 0.139
Sun Venus 650C, 10 round 15g spokes, Shimano hub 0.130 0.139 0.165 0.145
Sun Venus 650C, 12 round 15g spokes, Shimano hub 0.128 0.141 0.170 0.146
Sun Venus 650C, 18 round 15g spokes, Shimano hub 0.156 0.165 0.189 0.170
Sun Venus 650C, 24 round 15g spokes, Shimano hub 0.154 0.167 0.192 0.171
IIRC ovalized spokes are the best in terms of aerodynamics. I can’t remember the source but they had some data and some ‘illistration’ about why an ovalized spoke creates less turbulence than a flat bladed spoke of smaller diameter. Of course this could have come from the Sapim website or similar.
OK a quick search and I found what I was remembering.
http://www.zipp.com/_media/pdfs/technology/spokeshape.pdf
And like I thought, please consider the source.
IIRC, the fulcrum racing 5 evolution and the fulcrum 7 use the same rim, same number of spokes, and either the same or very similar hubs. Both have exposed nipples. The fulcrum5 has bladed and the fulcrum7 has round.
In this test, the fulcrum5 took about 5 less watts to hold 30mph.
http://www.rouesartisanales.com/article-15505311.html
It could be a number of things, but I’m telling myself it’s the spokes since I just spent the extra money to build a powertap wheel with CX-Rays 
I haved noticed in high cross winds that bladed spokes can make the bike a little twitchy.
The key is that oval spokes have better aero properties, and no real disadvantage vs. round spokes (other than costing more). Spokes fail a the ends (where bending forces and fatigue are greatest), so ovalizing the middle doesn’t impact the strength or durability.
I’d say the advantage is worth the $100 front rebuild…better ROI than the dimples.
I haved noticed in high cross winds that bladed spokes can make the bike a little twitchy.
Freaking what? I have ridden everything from an Open4CD w/28 2X Wheelsmith blades to an 808 in the wind…cant say one was more twitchy than another due to wind…
In my front wheel arsenal currently…
Hyperion
Neutron
Shamal HPW12
Vento
32 - 3X Mavic Open Pro
32 - 3x Mavic CXP33
Easton (something radial)
Zipp 404
Zipp 808
Cant say that anyone is more twitchy in the wind…and the rim face is far more exposed than the wind.