We didn’t try to separate CDA from CRR so I suspect it’s more CRR related than aero. If so 45/36 * 1.1 = 1.4w.
I’d call them a tie to be honest.
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Marc, just to clarify to understand
you tested ~35km/h, in order from fastest to slowest (inclusive of both rr and aero effects). This is for both wheels combined (?)
- Corsa Pro Speed
- GP5000TT (+1w from 1)
- GP5000s (+6w from 1)
- Corsa Pro (+6w from 1)
You saw similar differentials at different road surfaces?
Closer to 36km/h ie 5h IM time.
Fastest was the 5000TT, the CSP, then 5000s, then CorsaPro
However the TT and CSP were so close, I call it a tie. We do measure vibration and the CSP has a tinkle more ONJs (inside joke for those the follow the hookless crap). The road was good but did have a few cracks. Drums, velodromes and roads will show different deltas between tires.
We did not do a full comparison of different tires on different road surfaces. We compared tire pressures on different surfaces but only across 2 tires.
We saw very clearly that higher pressure (5.5bar) was better on better road surfaces and low (closer to 4) was better on the really bad surfaces. IM Canada is a mixture of good and GazaLike roads. He will ride IM Canada mid to low 4s
Goal was not to get uber accurate CRRs but to pick a tire for IM Canada.
Great info Marc. Thank you
How much does he weigh?
25 front and 28 rear?
He is 78kg
He will ride 28 / 28.
Probably a DT Swiss front and Premier Disk on the back
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I’m on board with all of what Marc is saying here: the Corsa Pro really isn’t the best choice. You could also go Michelin Power TT, they’re nice and fit in speed wise with the Corsa Pro Speed/5000 TT options.
Schwalbe Pro One/TT are usually in between those two sets (of race tyres vs more training/endurance focused tyres).
Would you be willing to share some of the vibration data between different tires/pressures?
Any chance you also have similar data for mass start depth wheels? 
Michelin Power TTs are my favorite time trial clincher tire, since I’m running an older non TLR front wheel. They roll fast and smooth especially with latex inner tubes, and have had far better durability than I was expecting (I probably have 1500-2000 miles on them with plenty of life in the wear marks, only one flat during that time which I discovered in transition after the race).
The only drawback that I’ve had with them is their cornering grip leaves a lot to be desired, and is really bad in the wet. A couple times even on dry roads I’ve almost wiped out going through roundabouts on the slight off camber turns. Both contis and vittorias have much much better grip. In most cases that doesn’t matter too much in triathlon, but if you do get a rainy day like at Lake Placid 2 weeks ago, you have to be pretty careful through corners.
When I eventually need to replace the Michelin Power TTs, I’ll likely go with the 5000 TTs for slightly better durability at similar rolling resistance. Also have liked rolling on the 4000SIIs and 5000s on my training rides and road bike.
I’ve been using a 25 mm Conti 5000 TT on my Flo disc wheel (19.4 mm internal diameter), but this data suggests it’s likely a 24 mm Corsa Pro Speed will be faster. When my current tire is ready to be replaced, I think I’ll switch to the CPS. Thanks for sharing!
I race short distance tri’s so durability/flat protection is not a big factor to me, plus I use sealant.
Anecdotally, my experience with the Corsa Pro Speed 26mm set up tubeless has been good. I’ve had zero flats so I can’t necessarily say it’s more fragile, but it is definitely less durable than other tires I’ve used. Went from no obvious damage to this after my 70.3 last weekend:
That was probably six 70.3s and one 140.6 plus the occasional prep ride. I used to be able to get much, much more out of the michelin power tts I rode before swapping to these and tubeless.
This is great. Thanks Xav. Hopefully you can include wider rims in the test to see how they perform, like Scope, Hed, PCW and the new Roval CLX Sprint which supposedly Remco used in Paris.
Yes we have wide rims in this test, it’s focused on deeper TT/tri wheels - the Reserve is the widest at 38mm, the Vision 91 is about 33.6mm etc.
We will be publishing data on that Roval wheel, but it’ll likely just form part of a road racing wheel data set.
Wider isn’t always better, and the 105% rule doesn’t work (as I’ve consistently said so!), there’s just no relationship between tyre width and rim width and the aero performance in this test. For example here is a subset of the data exploring that (excluding the Reserve as we used a different tyre, 29mm not 28mm so it’s not a fair comparison):
https://aero-coach.co.uk/cycling-wheel-aerodynamics-105-rule-is-it-true-with-modern-wheels
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This is great… at a quick glance in this test, it looks like the best aero was probably >110, right?
I get “wider isn’t always better.” But is it fair to say that wheel width greater than the tire’s measured width is mostly better? (Only one combo looks like it had a tire narrower than the wheel, and its CdA was not special.)
Is every dot on this chart a different wheel ?
I think that wheel at 93% is a good example actually, it’s 5th on the ranking out of 9 in terms of CdA, so there are 4 wheels worse than it which have tyres wider or equal to the rim and 4 tyres better! Of course a 30mm tyre on a 20mm wide wheel will be terrible but when you start getting closer it’s not so clear cut.
The fact that the best/fastest wheel is 113% and there are two wheels slower at 112% and 114% really highlights how it’s just not a metric to determine speed.
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Yes that’s right
so basically at this stage the 105 %rule is a " scam" lol
I’m not sure this proves anything. I think you would need to test varying tire widths (<100%, 100-110%, >110%) with each wheel to really prove out the 105% rule doesn’t apply.
This is what I am trying to wrap my head around
The highest CDA wheel is 112%, the lowest CDA wheel is 113%. Both have the same external rim width.
All this shows is one wheel is faster than the other, and unrelated to 105%
What am I missing ?