Spokes & Aerodynamics

[PpPete]

It's often said that reducing the number of spokes reduces the aerodynamic "drag" of the wheel.

Does anyone know much quicker a wheel is, with say 24 spokes, rather than with 32 or 36 spokes..... assuming all other factors being equal. Obviously the weight won't be the same - but I'm interested in the just the aerodynamic component.

And how much better are bladed spokes as against double-butted?

I can well see that at the top end of the sport all these "incremental improvements" are going to help but does it really make that much difference to us mere mortals ?

 

[yashicamat]

I wouldn't have thought the difference is that big. Aerodynamics are all about the rules of diminishing returns, so it'll be at high speeds that the differences will become increasingly apparent (I'd guess over 25mph at least before it becomes noticeable). I would have though that, for example, the change in frontal profile by using a different helmet, smoother clothes, slightly narrower tyres etc. would have a more significant effect (but I might be wrong - this is all speculation!).

 

[RecordAceFromNew]

The latest research I have seen indicates that while their effect on power requirement can be huge, it is not very significant at below 20 km/hr, which I guess is what you want to know.

You might also want to see some earlier States side research by Zipp here and here.

 

[Will1985]

I can notice a difference between 21 spoke bladed and 28 spoke round (Campag Zonda v Mavic OP) which are similar weight wheels. It's more obvious to me at a steady speed rather than accelerating. I ride my Zonda during windy TTs and also for training - if I remember I'll swap it for an Open Pro soon to see if the powermeter shows a difference.

Taking it to the extreme, my Hed 3 is super fast once you're above 40km/h with the optimum yaw angle