tri-spoke wheel

[WorkonSunday]

Hi all, I swear i try to google this many many time but without finding a conclusive result:

as far as aerodynamic goes, the deeper the profile the more aero it is, so where does the spoke design comes in? I mean those big tri-spoke/ 4-spokes/ 5-spokes design used by pro bound to have some important factor/advantages? but at the same time, if the advantage is overwhelming, then Campag doesnt offer one? or i got completely wrong end of the stick? it's for stiffness or other factor? please help a confused newbie.

[alcatraz]

I read that a trispoke is faster at wider yaw angles and that a deep rim is faster at low yaw angles.

I chose an 88mm front because I like to be able to true the wheel and it feels a bit safer. I've seen some trispoke wheels fail.

[mrlobber]

Choose Aerocoach/HED Jet 9+ front for an ultimate speed on TT.

There are talks about "watts required to spin the wheel", which "supposedly" favor tri-spokes and other wheels of similar construction, but these effects haven't really be quantified and proven to counter the tri-spoke less aero vs a deep section low-spoke count wheel.

If you have money to burn, buy both, race similar time trials, compare speed, wattage and CdA, and sell the slowest

[hambini]

I am highly critical of wind tunnel tests that many cycling companies carry out because they try and model very erratic random outside conditions in an inert wind tunnel environment. Critically, they do a good job at convincing people. Call me a cynic but I see lots of "school kids" who are in the early to mid twenties who are fresh from university and think the wind tunnel is the be all and end all of testing. I regularly send graduates that I train to the field to learn the difference.

Generally, a disc wheel will always be faster than any deep section wheel. This is not in any way due to the profile, it is due to the controlling nature of a solid surface. On a disc, the entire surface is solid and air cannot penetrate it and therefore be disturbed by it. In contrast, a rim has a detachment point at the rim, spokes and a hub to further churn up the airflow and then reattachment or disturbance at the rear.

When you get to 2 or 3 spoke wheels, these are generally used on the front wheel. The general guidance I would give is based on two factors - how fast you can go and how windy it is. At above 50km/h sustained speed, then a 2/3 spoke will be faster but if you are going slower than that or it is windy, you may have a job steering.

In a wind tunnel, the 2/3 spoke wheel will be perceived to be faster but that does not take into account the local and global vectors of wind.

Hope that helps
Hambini

[WorkonSunday]

Thanks for your input guys.

Is there any reason why these bigger spokes wheel are faster in the straight without side wind? or just simply smaller, but multiple stokes design will whip up alot of turbulence? cheers.

[mattr]

Two or three mostly aerofoil profiles are more aero than the egg whisk that is a spoked wheel.

[hambini]

MattR's one liner hit the nail on the head.

[WorkonSunday]

i see. thanks for the sharing your knowledge!