Maybe I'm reading it wrong but it looks like the crossover is closer to 26 or 27 kph, not 35? The Vittoria and R4 crossover around 35 though.

When I say climb I'm talking about the finish of stage 1 of Tour of the Gila or bigger, those little things that you go over at 9 jigawats are rollers. I have cut the weight to the absolute limit and I can't train any more than I do without quitting work so the only thing left is the little stuff.

Gotcha. I have done that climb at gila! (to get up there to spectate the finish, haha)

Yeah so the trick is, yes the vittoria is the faster tire up that climb, but just barely since rolling resistance is so low at that speed too.

So, better to conserve energy on the way there? Probably the difference is too small to even matter really.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

...if you're running Flo30 wheels and your wheel load is 38kg :-)

The "moral of the story" is that tire and wheel selection needs to be made in concert, not just one or the other ;-)

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http://bikeblather.blogspot.com/

In road bike racing, I find the differences in Crr in tires to manifest themselves in situations like I described in the blog post...you're in group going up a "medium" grade (i.e. aero drag is REALLY low) and you're trying to stay with that group. An "extra" 5-10W or so in that sort of situation can make all the difference in the world...

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http://bikeblather.blogspot.com/

What is the wattage difference between the vittoria and 4000S in that situation?

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Nearly nil...I was talking more of the comparison between those sorts of tires and something with much worse Crr.

For example, that's the sort of situation I realized that the new CXR80 Yksion tires were so bad, before I even put it on the rollers...

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http://bikeblather.blogspot.com/

Definitely. If you are constantly coming out of the aerobars to keep your bike under control, you'll lose more time breaking the aero position then you'll gain from the FLO 90. The rider is the biggest contributor to drag in the entire equation. If "you" aren't aero you can really mess the whole system up quickly.

All the best,

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Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling

Had 2 new gp 4000s that I got a good deal on which I weighed and an old one that has been on my training/ race Powertap wheel that have been using for 1 year with no issues at all.
New tire 1 - 203grms
New tire 2 - 215grms
Old tire - 184grms
I was goin to go with the logic of putting the lowest weight tire on wheel but judging by your testin this wouldn't make a difference it would've been interesting to know the weight of old tire originally but would be surprised if it was much over 200grms

I tried to follow the whole thread and couldn't find a definite answer to my problem

I'm racing IM Lanzarote in a few weeks, the course has 2400m climb, rough roads and winds of about 40kph. I expect a time of 5h00 to 5h10 but you actually spend very little time at average speed, you are either going very slow or very fast most of the time.

I will use jet6/jet disc C2 wheels.

I was going to ride vittoria tri tires and now I'm trying to decide if a gp4000s would be a better choice for the front wheel.

I also have conti supersonics both in 23 and 20 but would prefer not to use those in such rough roads unless they suppose a real advantage...

can anyone help me out?

alvaro
planetatri.com
twitter.com/alvaro153

As I recall you're on the lighter side of the adult male spectrum?
GP4000s advantage kicks in a lot sooner for you than it does for someone bigger (like me) - it seems likely that it would be the faster option on the front for you.

I'm 65kg

could you explain that a bit more? I'm I less affected by crr because I'm lighter?

Using the Flo30 data and my CRR testing we get this comparison for you on a rough road at 5hr pace with 12kg of kit:



Then me:



You can see that for me the lowest CRR option is best as the more aero combinations never surpass the Vittoria pair.
Whereas for you there is a decision to be made between the low yaw advantage of the Vittorias vs the better high yaw performance of the aero/crr fr/r combo.
Given that you said there are high winds it is likely that you will be in the high yaw scenario that kills the Vittoria (as a front tyre at least) so a GP4000s on the front would be sensible. But you can see that the GP4000s pair never gets to the point of being your fastest option.


This is all assuming that the Flo results map to your Heds. Shouldn't be far off given the similarity in design. And assuming that you can find a GP4000s with the CRR that mine have - you might get lucky and find one like Toms (which seems to be extra fast) or unlucky and get the dud batch.

thanks a lot!

I think that the biggest assumption is that the flo30 data maps to a jet60... design is similar but It seems logical to me that tire shape affects much more a shallower wheel than a deeper one, as the tire is a bigger part of the whole shape...

You must have missed this, but I've tested 3 separate GP4000S tires now, and they all rolled the same for me:

http://forum.slowtwitch.com/...ing=gp4000s;#4531076

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http://bikeblather.blogspot.com/

does it make sense to use the avg speed to perform the analisis?

as I said you spend virtually no time at 36kph, the course is all up and down so you are either ridding really fast or really slow... intuitively it makes more sense to me to optimize the equipment for the slow sections...

I posted my own results on that thread, and the 2 4000S tires I just tested rolled much slower--around .0007 slower than 2 Evo Slick clinchers. They're also about .0009 slower than the Evo Slick tubulars I've tested, which makes a Stinger 6/Evo Slick look like an attractive option, at least for road racing. To get Crr that low on a tubular though, it's not a great option if you need to fix a flat mid-race.

There still seems to be high variability in the Crr of the Conti tires.

You're testing on a narrow rim? Could it be that the stiffer sidewall construction (comp to Vittoria) of the GP4000S is penalised significantly by the reduced bulb effect on my 23mm rim?
I recall Damon mentioning testing the varying deflection of tyres on different rim widths - would be interesting to know the variation in effect for the different styles of construction.
I am planning to also test on a 20mm mavic rim to see if that is potentially the source of the discrepancy.

tell me again how you data mine weather sites to determine average wind yaw for a certain IM bike course?

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

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It's terribly sophisticated...
I just hunt for a site close to the course then enter the data for the appropriate day and time into the model. One hour blocks starting from the time of the end of the swim and the model factors in the ride time (so a 4hr rider doesn't get the conditions for hours 5+).

in the predictive sense how many years of data are you taking?

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

I tend to look at it historically. For my home race IMNZ there has been a massive variation in conditions as the race is timed for the change in seasons (to Autumn). So I like to consider the various scenarios to give a range of possibilities.

If I am looking to give an indication of the most likely conditions for a particular race I look at a couple of years of monthly averages for the location. I don't get too fussy about predictive scenarios as the weather is unlikely to be that cooperative.

Not likely (based at least on AFM's data on the subject) and if anything it should slightly improve the Crr on smooth surfaces, not increase, since there would be less deflection for a given load.

I'll probably be looking at the affect (if any) in the near future. I want to try a few of the IRC tubeless tires, and I'll be setting up one of my Zipp 101 rears for that purpose. Before doing that, I plan on doing some narrow rim vs. wide rim measurements with the same tire since my typical test wheel is rimmed with a narrow Mavic Open Pro.

I'm wondering if some of the differences may possibly be in temp compensation methods?

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http://bikeblather.blogspot.com/

OK, I see.

In looking at my target Ironman the winds historically are consistently out of the southwest on average (south to west, but mostly from the SW) and the majority of the bike course runs ssw to nne out and back. without running a model, I'm thinking low yaw angles on reasonable pavement, giving the edge to low Crr tires over a more aero tire, and not penalizing my Cervelo P4 too much over a P5 or Trek SC or some other bike that "sails".

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

Which course?