3w slower with the same tire pressure or dt swiss at optimal tire pressure and zipp at max 5 bar pressure?
Jeroen
Both at 5bar because that is what he will race at due to bad roads
On good roads he would have lost additional watts
You will like this.
He REALLY likes his Blue Noosa tri suit. In his mind, his other kit, Black Vanquish suit is black and like so many AGers, “how much difference can a suit make”. So I “convinced” him to test today.
2 runs Blue, 3 runs Black, 2 runs Blue
So his beloved “Blue suit” was costing him 2.75minutes at his IM pace
I told him, he looked at me, put on his running shoes and went running for 20mins, came back, “Black suit it is”
Eventually I can tally up all the 3 and 4 watts
Shit, i’m not sure if i like this or not:-).
As you tested just the 3rd iteration of the suit and there are still some details to adjust and improve i might need to pick this up.
I feel like its going to cost me more money :-).
I’m so glad the bike, the bar and the aerobar are done in design and already in development / production of the first samples…
Jeroen
This is a slippery slope and there are moral obligations you have towards friends and the public Marc. It cant be aero at all costs. Next thing you will have him in the giro aerohead 2 in the name of a few seconds…
Pondering some testing of helmet ventilation/heat dissipation myself. Could you expand a little on the testing setup here? Did you get consistent temp-readings from inside the helmet? Is it difficult to analyze them with regards to power output (and thus the thermal heat dissipation from the head) and external wind speed?
I would guess the thermal performance of helmets could vary with speed. Most helmets would give sufficient ventilation in say 50 km/h, but not so much in 10 km/h. For an upcoming multiday-event in the alps i’m considering the evade vs a more ventilated helmet and the consern is the climbs at low speed. For more flat riding I feel the evade always have sufficient ventilation, but perhaps not the same in low speed.
Will try to test inside on the rollers later, with the evade and giro aeries, with some sort of thermometer inside the helmet in addition to the core sensor, power and ambient thermometer. Not sure if i’ll be able to use the core sensor inside the helmet, would probably be the best.
Sure. First of all our main goal was not temperature measurement. He have a helmet sensor that’s primary goal is to measure head position/movement. This allows us to see if the rider is holding the head position we want or previously tested with. In sits inside the helmet.
We simply threw a small thermal sensor on it. It’s maybe 1mmx1mm, costs a few bucks, so we did it for fun. We do see different results. The Ekoi helmet with no vents does get warmer. I say “warmer”, we have been looking at the delta between the in helmet sensor and the aero sensor (outside helmet).
Is there a delta ? Yes. How useful is it…not sure
We do a test run and they are usually at relatively constant speed.
Is it worth correlating with things like core sensors ? Maybe…but we are far from knowledgeable in that field. We just thought it would be interesting to throw a small therometer on our helmet position sensor
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Trust me, if I could have got an AH2 I would have fudged the numbers to get him in it purely for entertainment purposes.
Reason : After a lot of work, I had convinced the wife we were getting a Rottweiler. My buddy, in one evening, convinced my wife that a poodle better suited us. It took me a week to correct the situation. That deserves an IM in a AH2.
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I moved this from another thread and decided to finished it. I promised to go easy on the data. Data is evil 
Last ride of the year done, so I wanted to close a chapter
In the month of August I started benchmarking my 2024 Cervelo PSeries (size 56) against a 2025 Ventum Tempus my buddy got for IM Canada. Later I decided to bring my 2009 Rim brake P2 into the comparison. There were over 20 days of testing.
When I started I just tried all 3 bikes “as is”. The PSeries had a decent cockpit (PD Aeria) but was a little messy on the cabling.
First tests done on the Ventum were on a super clean bike but slightly off in terms of fit. I took my buddies fit and my saddle height. He rides shorter, higher.
The P2 was a mess in cabling
But all along, the bikes tracked pretty close. There was never a “20 watt difference”.
I slowly cleaned up the bikes and zero’d in on optimal setup, fit and components.
At the end of the exercise the bikes are really really close. I did final tests, skin suit, race helmet…
At the end PSeries got gold, Ventum Silver, P2 bronze, by very little, but not because they are faster in that order. I will explain
If we go purely from a CDA perspective, the P2 is as good as the other two after full optimization (optimal fit and a new bar). The problem was tires. I can only put 23mm tires on it and had a set of GP5000. The other bikes had GP5000 TT which is a faster tire. So if I compensate for RR differences, the P2 is as fast. But the fact you can’t get fastest rubber for a bike is a handicap. We are talking roughly 2 minutes on an IM. We’ll keep ‘data’ to ‘minutes on a IM’
The PSeries ended up fastest. But in the back and forths, especially when I put my buddies cockpit on my bike, “reach” helped and I could get most reach with the PSeries (and P2)
So at identical fits, they were almost identical. The PSeries (and P2) reach helped.
However the PSeries was upgraded with a PD ultimate bar which cleaned up the cabling and allowed SAFE extenders for the reach. Sketchy extenders scare me.
For my fit, the Ventum could have benefitted from a bit more reach. But what I like the most about the Ventum is it came well spec’d. I think PD may have more reach options coming and this will help the Ventum.
In the back and forths, the profile design ASC 53 and ASC Pro ended up being compared. At first I didn’t see it but eventually tested a bit faster and was more comfortable. The ASC Pro came with the Ventum. I need to convince my buddy he doesn’t want them.
Testing and comparing on different days is not without its challenges. But I got good reproducible data.
I got sidetracked multiple times. I bought an Evade 3, I tested 5000S, 5000TT, Archetype, Corsa Pro, Pro Speed, 25, 28,30s. Ha, I’m full optimized for next year
From
65 font and back , LGP09 helmet, normal suit, original stack and reach, messy cables
to
65 front, disc, modern helmet, skin suit, about -2cm stack, about +2cm reach, new cockpit and clean up
There is a 12minute difference over a 5hIM.
Summary
- The bike makes little difference
- Optimize what you have
- Buy a bike with the right components from the start
- Fit is critical.
- Don’t believe the hype at so many levels
I probably did my last ride of the year yesterday so you won’t have to endure more data 
this was the P2 pre cleanup
the PD bar allowed to move many of the cables internally. A move to SRAM would get rid of the DI2 10 speed junction box taped to toptube. The is the PD ultimate bar
P2 after lceanup
PSeries pre cleanup
Got rid of blipbox
Got rid of all cables. I do need a new cap to hide that last cable behind the stem (on order). It has to be dremelled.
this cockpit, taken from the Ventum is the ASC pro and ended up testing a bit faster
No cables anywhere
I am a crappy photographer
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This is great stuff.
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What was the final conclusion on the Corsa pro speed vs GP5000TT?
I know you had mentioned you though the gap was pretty marginal despite what the BRR data says.
when I calculated CRR, I got .0036 Corsa Pro Speed vs .0037 for the 5000TT
However I didn’t pry apart CDA and CRR. the ProSpeed maybe say 2watts faster in CRR and 1 watt slower in CDA for a net 1watt. In this test I only measured the net.
For some tires I have tunnel data to pull apart the values. I don’t with the Vittoria tires. But at the end of the day it is extremely marginal overall and I am not convinced on durability. So I go with the TT
Of all the tires I tested this summer, the CorsaProSpeed is the only one I can’t get to seat after many on/off/on/off……
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Thanks Marc! Super insightful!
Aerocoach just published tire aero data for the Corsa pro speed and GP5000TT (in 28mm) on their new wheelset, and found the Corsa Speed was about 1W faster for some reason (quite different to the conventional thinking with Contis tread).
Your milage may vary as you were in a different set up - the conclusion is that isn’t a lot of difference between the two choices.
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Amazing. Just wanted to say thanks for sharing and the write up.
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Fortunately we have some narrow SuperSonics in stock 
Did you test both bikes with the same aerobar angle? In the picture they are quite different.
But a great write up and again it is proven that it at least seems we are at aero peak on bike design.
Jeroen
But what if we like data……
Any chance of a table showing the steps of time gains?
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yes absolutely. Those pics were taken early in the process. As I said, I just rode what was there
but as I progressed I made sure the bikes were as identical as can be. As a matter of fact the differences at first gave me ideas of test routes to go down.
Peak aero will come when the bikes allow us to change what really matters
BTW, 39 test days since August
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I can try to break it down
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