Can't wait to see crr factored into the aero data.

That's coming...I've got a box full of S-works Turbos and both sizes of Turbo Cottons waiting for me to spend some "quality roller time" ;-)

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Thanks for testing the old H3/Specialized TriSpoke. While the new wheels are definitely better at higher yaw, it is cool to see that the H3 is still competitive in the 0-5 range. Can't wait to see what the in-frame numbers look like.

Unfortunately, due to time limitations, the H3 wasn't one of the wheel/tire combos tested in the bike :-(

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That's awesome Tom! Thanks to you and Specialized.

Also double thank you for reporting the data as CdA! In case anyone doesn't know, CdA is the drag coefficient in m^2. Good TTers are close to .20 and triathletes tend to be closer to .30. So the front wheel as measured here is ~7-10% of your total drag.

You can thank Chris and Cam (and Mark Cote too) for the reporting in CdA. That's the default output value they use.

Speaking of total CdA...you may find if interesting that when we did the "rider on" testing, my CdA was measured nearly smack dab in the middle of those 2 values...

...on my road bike, in the drops :-)

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Is that an S5, aero helmet, and skinsuit? Still really low.

Nope. That's with a trim fitting road kit, LG Course helmet, on the Venge ViAS with a single round bottle, Roval CLX64 wheels...

...and the CdA was only slightly higher on my custom steel Stinner (set up in "crit mode" with a Virtue bottle)

:-)

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There are some surprising results in there.

Most notably how good the Roval wheel is. I've liked the SW Turbo for a while; have been running it as a "crit" tire in 24mm mode. The Specialized outside rep showed data (that I haven't seen since online...maybe?) suggesting it was as fast, crr wise, as the GP4000s II. Aero properties notwithstanding, seems like a good tire choice.

Thanks for this! Very interesting

testing against a cc wheel, you..... really?? :)-

Well...this testing WAS just about aero, and you'll notice that there's a similar depth wheel with a metal, textured braking surface that basically ties it with the same tire.

Now, when judging overall performance, it's not just about the aero, right? ;-)

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depends on the event and weather conditions :)

need to read the specs on the roval, ie rim depth

can't test power to spin there?

edit: also I would be curious if the black jet performs any differently than a regular jet+ due to the braking surface treatment

I'm surprised to see such a large difference between the Hed 6+ with 24mm Turbo Cottons and the Hed 6+ with 22mm SWorks Turbos.

I guess I would have expected something more similar to what you saw with the Zipp 101 rims. I'm not too familiar with the tires, but from their website the tread pattern looks pretty similar. Are the Heds just really sensitive to tire width?

clincher only? or might you take a look at their tubulars

There are some surprising results in there.

The 24mm Turbo Cotton does poorly like all the other "open tubulars". Surprised that it was that bad, though.

One that seems odd to me is the Attack vs 23mm SS on the Flo 90. Really would have expected the Attack to win there. I guess at high yaw it does, but the SS is better at law yaw.

As I wrote in the text of the blog (you READ the text, right? ;-), THAT particular Turbo Cotton is my personal tire that had ~700 miles on it at the time of testing, so a big part of that is going to be due to wear and "growth".

The week after I had my tunnel visit, Cam Piper spent some time and did runs of each S-Works Turbo tire width and both Turbo Cotton widths on the Roval CLX64. In that case, the 24C Turbo Cotton plot was offset from the 22C S-Works Turbo by only ~.001m^2 between +/-5 degrees, or basically the same as the 24C S-Works Turbo. The 24C SWT does perform better at 10 and 15 deg than the 24C Turbo cotton though...but, is it enough to overcome the Crr difference?

That will be all gone over in a later blog post :-)

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Tubulars have VERY limited applications IMHO...and TT/Tri speed isn't one of them ;-)

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Yeah, I was surprised by that one as well...with the significantly lower Crr, and the "hit or miss" Crr performance of the Attacks...it's kind of hard to argue against the 23C SuperSonic as a front tire on that wheel.

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Tom,
How was the Attack mounted? IIRC wasn't is suppose to do better aero wise mounted backwards, or was that just a bad dream I had, hmmm!

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Mounted as marked. I did recall the data showing "backwards" may be faster (Swiss Side testing?), but there wasn't time to try both ways so I ran it the way most would mount it.

edit: I found the apparent source of that "Attacks mounted backwards" meme (I think): http://www.swissside.com/...n-project-update-13/ ...although, I think it's probably a bit of a stretch to apply what they saw with the GP's to the Attacks. Yeah, the tread patterns are slightly similar...but...

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I read the text as well, although I didn't think that 700 miles would make such a big difference either. Do you have a picture of the tire? Is it super squared off?

How does Crr usually trend with use?

It's not "squared off" in any appreciable sense...it was used as a front. I suspect the big difference is from size/shape changes just from being mounted/inflated/flexed for that period of time. That tire measured between 0.3-0.5mm wider when mounted than a brand new tire.

Crr typically drops with use...again, partially due to size growth, but also due to the tread thinning from wear.

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did you mean 3-5mm, as 0.5mm is about 1/50 of an inch and on my 50 scale "ruler" that is not much

.3-.5mm is a decent amount when we are talking about tire casing stretch.