Disc vs deep dish

Triathlon Forum
1

I’ve been searching for any studies related to the increase in speed when using a disc rear wheel vs a deep or semi deep section wheel.
I’m interested in getting a disc or deeper section rear wheel but really want to do my homework first.
For what its worth…I ride a set of DV46 UL Tubulars. I am simply trying to justify making jump to an SDV 66 or Element disc (or Zipp 808/disc…etc).
Any guidance appreciated.
Cheers.
Kyle.

2

HEDs interactive chart provides a good indication

http://www.hedcycling.com/aerodynamics_technology/

In summary a disc is almost always better

But, you don’t have to spend a lot, you can just get a cover for whatever rear wheel you have now.

3

HEDs interactive chart provides a good indication

http://www.hedcycling.com/...dynamics_technology/

In summary a disc is almost always better

But, you don’t have to spend a lot, you can just get a cover for whatever rear wheel you have now.
I’m not sure how accurate (unbiased) this information is. A lot of sources report a Zipp Sub-9 to produce negative drag at 15*… this reports that it actually requires about 70g. Hmmm… maybe HED.'s testing was a little different than Zipp’s.

Good resource, though.

4

Almost all wheel tests is done with the wheel in a fixed “front” fork. I have only seen a few tests where the back wheel is…back, mounted where it belongs on a bike.

These tests with rear wheel on bike tells a bit different story:

  • Here on slowtwitch someone published a test where H3 deep performed equal to a rear disk.
  • When Lampre tested the Cento Crono a spoked Fulcrum wheel performed better than the other options (including Zipp disk…)
  • A German test on track where the old Xentis wheels performed better than Zipp 909. (The downside of this test was the lack of wind).

I don’t draw any conclusion - could it be that the difference between good rear wheels are very, very small when used on a proper designed tri-bike?

5

I dont think we’ve seen a “real world” independent test that is "good’ enough to make a determination. If only my school wasn’t too focused on running and swimming. DAMN THEM! I guess it isn’t enough that Indiana University is the home of the Little 500. Well myself and a few other graduate students are working on some funding to hopefully change that (well lab testing anyway…road testing will be down the, well road).

6

ajo makes some good points, and I can’t refer to any study where a disc was tested as a real wheel–I suppose that would commit you to a particular bike. However, it has been argued that a disc provides a surface for turbulent air to reattach. That’s one reason that a disc may in fact perform comparatively better as a rear than testing in a front fork would suggest. Certain bikes (seattubeless designs if I recall correctly) are reported to be much more slippery with a disc.