Aerodynamic Drag of Wide Tire on Box Section

[RyanH]

Has anyone seen wind tunnel data that they can post here of what a worst case wheel looks like? Thinking 32 spoke Nemesis with a 27mm tire. It seems that a Hed Belgium with 23mm Conti tire is only a few watts slower than a Zipp 303:

[Calnago]

Sheesh, I don’t think I’d ever run a 27mm tire on a Nemesis rim. 25mm is pushing the limit. I find the best size is 24mm on that rim, so you can still get the wheel out easily when you release the brakes. Aerodynamically it certainly won’t be the fastest but I’ll tell ya... I doubt there’s anything that’s going to be more stable coming down that windy mountainside.

[svendsvin]

from zipp 303 2008 promotion:

more here from silca

[svendsvin]

or some of the tour magazine tests:

The worst one here is an open pro rim with 32 round spokes (and probably 23mm gp4000s ):


or here the worst wheel is a mavic reflex with a 27mm tubular on and 32 spokes:

[NovemberDave]

https://novemberbicycles.com/blogs/blog ... lculations This baselines a Velocity A23 versus some other older shapes.

The width of the rim has an effect and the spoke count has an effect, as does the gauge of the spoke. We measured a 1w difference of 1.5mm mid section Lasers vs CX Rays (same # of spokes), and Flo measured a bigger difference comparing straight gauge 2.0mm spokes vs CX Rays.

There’s a lot of info out there, you just have to take all of what’s credible to you and distill that into your best answer.

[patchsurfer]

27mm paves on nemesis are possibly the plushest, most special feeling sunday getting lost type ride thing going...

[bm0p700f]

I use 27mm paves on my nemesis but they only measure 25.5mm wide.

[svendsvin]

3t exploro launch had some graph for 28mm road tyre vs 40mm :


I think it is tested at 20mph

[Beaver]

Very wide tire on a low and narrow machined box-shaped rim with as many thick square-cut spokes as possible.

[hambini]

I have never really understood why bike manufacturers neglect to tell the customer that when they test, their increasing yaw angle is effectively reducing the forward speed.

ie 50km/h at 15 degrees is actually 48km/h

You'll also get a different line if you are coming from attached to detached (0 yaw to 15+) vs detached to attached (15+ towards 0yaw).