tri-spoke wheel

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WorkonSunday
Posts: 109
Joined: Tue Jan 16, 2018 4:39 pm

by 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. :oops:
In the house: Colnago V1r, Colnago A1r, Wilier Cento1 Air, Scott Scale 700SL, Bianchi FSE, Colnago Concept, Colnago A1r, Specialized Ruze Pro, Wilier GTR

by Weenie


alcatraz
Posts: 2153
Joined: Mon Aug 29, 2016 11:19 am

by 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
Posts: 941
Joined: Sat Oct 23, 2010 9:36 am
Location: Where the permanent autumn is

by 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 :D
Retired bikes: Cervelo S5 2015 / Felt AR FRD 2014 / Cannondale SS HM 2014 / Scott Addict SL 2014 / Scott Plasma Premium 2014 / Orbea Orca 2008 / Look 596 /

hambini
Posts: 490
Joined: Tue Nov 15, 2016 8:13 am
Location: Cologne, Germany

by 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
Hambini Aeronautical Engineer, Polluting YouTube since 2016 - views expressed are my own...
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WorkonSunday
Posts: 109
Joined: Tue Jan 16, 2018 4:39 pm

by 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.
In the house: Colnago V1r, Colnago A1r, Wilier Cento1 Air, Scott Scale 700SL, Bianchi FSE, Colnago Concept, Colnago A1r, Specialized Ruze Pro, Wilier GTR

mattr
Posts: 4673
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

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

hambini
Posts: 490
Joined: Tue Nov 15, 2016 8:13 am
Location: Cologne, Germany

by hambini

MattR's one liner hit the nail on the head.
Hambini Aeronautical Engineer, Polluting YouTube since 2016 - views expressed are my own...
Add me ON TWITTER!
Aerodynamic Masterclass in bicycle wheels
I fixed the bottom bracket from hell

by Weenie


WorkonSunday
Posts: 109
Joined: Tue Jan 16, 2018 4:39 pm

by WorkonSunday

i see. thanks for the sharing your knowledge! :thumbup:
In the house: Colnago V1r, Colnago A1r, Wilier Cento1 Air, Scott Scale 700SL, Bianchi FSE, Colnago Concept, Colnago A1r, Specialized Ruze Pro, Wilier GTR

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