just to confuse this even more....

I think it's important for anyone else looking at your (excellent, btw) chart is that the break point will be different based on rider weight and position. For instance, someone like me (a 62kg rider with a very rearward position) is in a different boat than a 200 lb guy riding a 90 degree seat angle.

I used Damon's 100 lb load and 1.5x "road roughness" factor to back out the aero drag at 30 mph. Rather than assuming a rho and solving for CxA, I just scaled the aero drag as the ratio of the apparent wind velocity squared over 30 mph squared (i.e. (Vw^2)/(30^2) )

But, once the "aero drag" is solved for, you can then modify the Crr drag for your particular wheel loading and "road roughness" assumptions and see how that affect things.

---

http://bikeblather.blogspot.com/

okay. For me that'd be ~250 lbs load ;-) which would change the intersection points or possibly remove some.

the 1/2*rho*CdA bit makes sense ...

Just for "giggles", I added 2 more "speculative" entries. The first is for a used VF record and the assumption is that it's aerodynamic performance will be the same as, or very close to, the Zipp and Bonty 21C tires. The second is for the same tire, but if it could somehow have the "wings" of the Aero TT added (with, perhaps, a bead of RTV?) and thus the same aerodynamic performance of the Aero TT tire. Again, this is for the 100 lb tire load case that Damon originally assumed.

It appears that the VF would perform nearly identically to the RXL Pro 23C tire, which isn't surprising since they have nearly identical Crrs and the aero drags appear to be similar as well. The performance of the VF, if it could get the aero drag of the Aero TT tire, is potentially outstanding. At 27mph, you're talking about a potential difference of ~70g of total drag force. That's equivalent to a time gain of ~.75s/km...or, ~30s over a 40K.

Enjoy.

---

http://bikeblather.blogspot.com/

Damon...I keep forgetting to ask, but when is the ACC wheel going to be available? The Bonty site says that they aren't available yet.

Also, is it possible to just buy a front wheel?

---

http://bikeblather.blogspot.com/

no quote this time to cut down on the trailing bits .. can you tell me where the 'wings' would be applied? are we talking the right down at the tire/rim interface gap? or further back up the sidewall?

interesting ideas! I have some old school green Axial Pro's home somewhere in a bag!

thanks! You're a fountain of useful info lately...

This is exactly what I was looking for in an earlier thread re: clincher v. tubie.

Yeah...that's the idea...filling the "gap" at the tire/rim interface right at the bead. Just look at Damon's photo above to see that.

Now...don't forget that the BIG ASSUMPTION is that filling the gap this way will be as effective aerodynamically as the "wings" on the Aero TT tire...AND it won't adversely affect the Crr either. There's some old data here on doing this, but by my figuring the advantage only comes out to be ~5 grams of drag at 30 mph from the value listed in the table under "fill the front tire gap at the rim".

Damon's data implies that it would be more like ~60g at 30 mph. Perhaps the advantage is greater with the deeper, more aerodynamic rim (since the flow is attached further along) than with (what I assume to be) a shallow profile rim with lots of spokes?

---

http://bikeblather.blogspot.com/

Yeah...I should probably "shut up" now...I'm just potentially helping my competitors get faster ;-)

---

http://bikeblather.blogspot.com/

You mention the wheel- was the Bontrager ACC. Is that the 5.0 model or just a regular box carbon rim or?

thanks!

hey Josh, this may have been asked, but........
say i have both the 808 and 1080 front wheels and the option to use either in an upcoming race. since your study is at 10deg yaw, and comparing to Hed's data on their own wheels, wouldn't the 1080 possibly be slower than the 808 at high yaw angles, but faster in low wind? looks like Hed's wheels are admittedly slower at high angles the deeper they are, so wondered if yours were the same trend?

[/quote]

---

i find this a bit strange that you not measure the CRR in the field and as you might know every surface has its own roll coeff and its not allways linear as you calc linear

---

http://www.ada.prorider.org
skype ceesbeers191053

Its funny to see ,that you never see a riders tested with back wind or any equipment testing ,i guess they never do or know anything from this.

And its good to see they they gone use tufts in windtunnel testing as we started that in using that begin of the 90th .
Well they need a dummy first meaby they finaly gone used it also with real riders.
And will take sometime they gone use realtime CFD in the windtunnel i guess will take them 15 years to catch up too.

---

http://www.ada.prorider.org
skype ceesbeers191053

I find it funny to see that the only times you post are to tell people about how they're obviously doing something wrong and that everything you do is years ahead of that...and yet, you never add anything constructive to the dialog.

---

http://bikeblather.blogspot.com/

hmm, the way i recall it they went from non-existant to top of the heap in less than 10 years......eh?

do you need any help patting yourself on the back? Geez ...

http://picasaweb.google.nl/...#5188847982716858626

---

http://www.ada.prorider.org
skype ceesbeers191053

Yep...that's constructive <rolleyes>

---

http://bikeblather.blogspot.com/

http://en.wikipedia.org/...le_image_velocimetry

---

http://www.ada.prorider.org
skype ceesbeers191053

[/reply] hey Josh, this may have been asked, but........
say i have both the 808 and 1080 front wheels and the option to use either in an upcoming race. since your study is at 10deg yaw, and comparing to Hed's data on their own wheels, wouldn't the 1080 possibly be slower than the 808 at high yaw angles, but faster in low wind? looks like Hed's wheels are admittedly slower at high angles the deeper they are, so wondered if yours were the same trend?[/reply]
anyone comment???

I think you should be able to find data that has the data for both at various yaw angles. IIRC, the 1080 continues to do better than the 808 as yaw angles increase. The 1080 actually bests the 900 disc below 12.5deg of yaw.

NORMALLY, deeper wheels are faster as you get into higher yaw angles.

---

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

thanks Jordan.......i think it was the Hed 3 that threw me, since it does better than their deeper wheels at more yaw. now that i compare their 60 and 90 though the 90 still does better all angles