Deep Section Front Wheel or Tri Spoke

Duncanandthemachine

Hi Folks,

What are the pro's and cons of running a tri spoke for TT's versus something like a Zipp 808?

Cheers,

Duncan

sungod

fwiw tour mag published test data on wheels a while ago, the 808 not only beat a tri-spoke, it even beat some disks, i pasted in the aero chart

you can access the complete article here...

http://www.tour-magazin.de/services/qtr ... 4.html#/96

chrisvanderkaap

i'd like to know too.

I suspect it has something to do with turbulence, I recon the the 3-spoke is more stable in sidewinds. But I don't own any to verify.

Anyone else?

chrisvanderkaap

after a google search I plucked this from velonews article "A Zipp Through Time"

"When one of the three spokes in a tri-spoke rotates into and fills the fork blades, airflow through the fork is restricted and dams up, creating a pressure wave. Furthermore, in a crosswind, the side surface area of the wheel changes, essentially reducing and increasing by one-third as each spoke moves into the shelter of the fork blades and then out again. The shifting center of pressure can cause instability in a crosswind. With a tri-spoke your benefit is from surface area, but that also works against you in handling. Even if the tri-spoke and deep section wheel are equally fast, the deep section will do it with a lot less side force and thus more efficiently. In a deep section wheel it’s about passing air through and across the bike and wheel as efficiently as possible and leaving it clean – not leaving wakes and turbulent air.”

mattmaximus

Interesting that the current TdF and Olympic champion seems to prefer the tri spoke. I can't imagine Shimano were very impressed that he rode an unbranded wheel so I reckon he must have insisted (that's imagining / reckoning without any actual knowledge of how the sponsorship thing works with pro teams!!).

Grill

Tri-spoke is fastest. At least according to those who ride it who happen to be fastest.

Duncanandthemachine

Hence the question, I though the tri spoke was dead, but wiggo and Froomie ride 'em when the deep section shimano wheels are supposed to be pretty descent. Tony Martin rides an 808 but is on a zip sponsored team. I reckon an 808 gives greater flexibility to ride in flat road races too...

Cheers for your thoughts guys.

mfin

To say which is fastest depends on the conditions. You've got all the yaw angles to take into consideration, plus the fact most TT courses have a return leg, which isn't the opposite of yaw angles at all, as the direction of travel changes things, then wind is never consistent in the duration of a race. Courses often aren't straight lines at all. Braking can make a difference on some courses too, plus wet braking.

I think they are so close on paper in controlled conditions that on a course you'd be lucky to tell. One might favour you over the other on handling, if you're sensitive to that. Most people aren't aero in the first place either. If people like Brad and Froome use them because they are a faster wheel then they must be kicking themselves that they ride a Pinarello TT bike that has a a load 3D embossed 'bunting' on the down tube, as that's interrupting the airflow for sure, in fact the Pinarello you can pick holes in a plenty for aerodynamic oversights if you look at it up close.