I think the thing that needs to be taken into account here (waving hands generally responding to all), is the conditions of roads. BRR has tested all the sizes and found no difference, +/- .2w, when all the tires are adjusted for sag. That however is on a mostly smooth drum and not a road. Vibrational losses start to add up as the road surface gets worse. I'd posit that a 26 and 28 will have very similar Crr on typical smooth-ish tarmac. The 28 will win out as the road gets worse and vibrational losses mount.

Another thing stated was that tires start performing worse at around 30mm, or Josh said something to this nature. We're already there. a 28mm on a 21 internal is just under 30mm. On a 22.5 internal it's slightly over 30. This is a New tire, after use they tend to expand a bit. For comparison a 25 on a 21 internal is ~27.5. A 26 is most likely 28.

Perhaps another thing to consider is weight of the rider. Vingegaard is child size. There less energy to dissipate than for the average or even elite triathlete. I have no doubt, given the amount of focus the team put into preparing for that TT that they wouldn't test all options and choose the fastest combinations for that rider.

Hopefully we can get some testing data soon on this new tire. I know there's also a Pista Oro Clincher floating around, but my sources have told me that it hasn't tested any faster than the VeloFlex Record on the track. Apparently Vittoria is still working on the compound. I think as a system the Princeton disc and Conti 25 TT is still fastest (track).

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Heath Dotson
HD Coaching:Website |Twitter: 140 Characters or Less|Facebook:Follow us on Facebook

I think (hope) we're about 15-20 years past that! At least on this forum.

There are 4 road sections this will be tested on. They asked "how do we pick then ?". Easy. Take the Silca calculator and pick 4 roads that match Josh's categories : new pavement, worn pavement/some cracks, poor pavement/chipseal, cobbles. Vibration will be logged

The riders are twigs, so I specifically asked for a "bigger" rider (75kg) and I have access to a "really really heavy" rider although a lot less pro than the others :-). I suspect I will have a 60 to 82kg range.

I figured you would have that sorted. My comments were kind of generalized to those making that blanket argument that wider is faster.

Another thing to note is when people say 25's are the new 23's and 28's are the new 25's. They're not wrong, but they're also not right in the way most think they are. I say this because, when the 5000's came out, the 25's were actually the same size size and 4000 23, the 28's were 4000 25, etc. Also of note is that the 5000 in a 28 and 30 are virtually iniientical except for the hot stamp. The reason is that the 28 is based on an ERTO of 19mm and the 30 uses ERTO of 21. I'm not 100% sure of how Vittoria sizes their tires.

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Heath Dotson
HD Coaching:Website |Twitter: 140 Characters or Less|Facebook:Follow us on Facebook

ST, perhaps, but IRL there are still people obsessed with wheel weight.

It'd be wrong to say that the 26c will be faster in all conditions vs. the 28c, or vice versa. But overall, I can say that typically the 28c will be faster rolling wise, especially at lower pressures and/or wider rims. Our recommendations in terms of pressure (check our website) is probably lower than what most calculators would suggest. When you add the additional comfort and grip advantage, this is why I run 28c both front and back - having anything smaller than 28c at the rear makes little sense.

Now, as always, the aerodynamics will substantially vary depending on the whole system (bike/fork/wheel...). If you see a pro team running 26c rather than 28c, you can assume that this was tested on the final bike set-up and on the actual course they'll be riding.

We'll look as to what we can publish in terms of actual (testing) data but I can confidently say that we have tested and worked with multiple partners on this last iteration. I've personally been very excited to see it get released!

If it'd be of interest and if we can pull together some specific topics, I'd be happy to do a bit of a Q&A.

Faster rolling at 28c but slower aerodynamics is pretty close to given. Which will win depends on the system (and the conditions, including speed).
If it was clear 28mm would be best, especially for rear, why is it at the edge of the offering? Why not go 26,28,30 instead of 24,26,28? My impression is while in the future the trend will get there, in many all-out-speed conditions with goad roads and current wheels the 26 might still be slightly ahead (but probably splitting hairs)

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https://besse.info/
https://www.strava.com/athletes/2012033

Yes, but did you consider rotational inertia?

When you say "this is why I....", and "If you see a pro team running 26c rather than 28c" is this for TT or road ?

We have a tendency to mix the conversations here and it is a different set of parameters, is it not ?

reporting back on an earlier question. i got this from vittoria:

"The 28mm wasn’t available yet at that time, in due time to complete the testing and acquire the proper confidence to race. While the testing started earlier on the 26mm."

this is the answer to the question of whether the 28mm was available prior to stage 16 of the tour last year. of course it's questionable whether they'd have chosen 28mm. if they would've chosen it i think the main reason would've been all the turns in that course. but it's moot. i think it's probably true that vittoria began with 26mm because it would be the most used tire by the pro teams. so there's that.

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Dan Empfield
aka Slowman

Silverstone sports engineering hub measured the Corsa Pro as one of the slowest tyres out of the performance all round tyres.

the corsa pro is a road race tire. BRR has the goodyear (a tire a ride and love) less than a watt faster than the corsa pro, but with a BRR puncture score of 33 compared to the corsa pro's 46. the conti is barely better. i think it's puncture score is 34. assuming that your chart is a misprint and the schwalbe tested was really the pro one TT, the only tire in that group that has a BRR puncture score in the range of the corsa pro is the michelin. so, i'm not sure that this chart is comparing tires of like use case.

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Dan Empfield
aka Slowman

I think the goodyear tire on BRR that beats the corsa pro is the F1 SuperSport R and not the regular F1 R. The regular R has an additional protection strip.

It's surprising that the F1 R did so well on the Silverstone test. It didn't do so hot on BRR.

In my case, I was referring to tri where the small aero advantage of the 26c doesn't offset the Crr and comfort / grip of the 28c.

Having said that, don't be surprised to see more and more pro cycling teams using 28c too on pure TTs this year but again, they'll test both and decide prior to the races what works best for each course.

Depending on the wheels, the aero differences could be far more than "small". I'm sure there are lots of folks on ST who can confirm that you can turn a great wheel, like the H3C for example, into a dog with the wrong tire.

This data is super suspect though, considering it contradicts other published data. In particular, both aero coach and bicycle rolling resistance show that Goodyear tire to be slower than both the Vittoria and continental tire, and the schwalbe pro one and pirelli tires have similarly been shown to be slower than continental at least.

Barring additional context, this really doesn't pass the sniff test.

i don't believe that graph, as labeled. i'm pretty sure the goodyear they tested is the F1 SuperSport R. i believe they mislabeled that and the Schwalbe on the chart. otherwise, the testing is very suspect. i'm pretty familiar with those 2 goodyear tires, and the SuperSport R is fast. the F1 R is kind of like the Corsa Pro Control. not fast. but when i ride the Corsa Pro Control i don't even take spares or a flat kit.

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Dan Empfield
aka Slowman

this is why i've always tried to frame my believe in the move toward 28 in the context of other equipment. frames and wheels need to be made to optimize that size. when i see new tri bikes made they tend to be made for 28mm tires (esp those with really wide-set fork blades). likewise many of the new wheels. notoriously it's zipp whose aero wheels now are made for 28mm tires. i think any time you have a wheel with an inner bead width of 22.5mm or greater, and an outside width of 30mm or more, that's likely a wheel that works well with a 28mm tire.

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Dan Empfield
aka Slowman

What size internal rim please?

I have a rim with 21 internal do you think the 28 is still fastest?

External width probably still matters more. What's the wheel in question?

Glad you asked, I am also wondering about running a 28 conti 5000 or S TR version for a Hed Jet+ rim. I wonder if it is too big a tire or not. I also have the newer Pirelli P Zero Race tire that is tubeless in a 26.

So, tire gurus...What do you say, 25 GP5k, 28 GP5k or 26 Pirelli P Zero Race (new one) for a HED Jet+ front wheel?

I'd use a 25mm on the front, the 28mm on the rear. I find that the 25mm gp5k inflates to about 28/29mm on a 21mm internal rim. This will pair better with the rest of the rim shape while also being wide enough to seal. A 28mm on the rear is more likely to seal successfully with tubeless and will still only inflate to ~30mm, which isn't too bad, still will provide a little damping.

Pirelli tires are slow everywhere I've seen, I'd definitely not race on that unless you're road racing cat 3/4 in the Pacific Northwest

Another smaller issue is showing labelled size. The Corsa Pro runs fully even numbers in labelled size, while those others mostly run odd numbers for 23 and 25 before switching to even numbers.

So comparing the Corsa Pro's 24 vs. everyone else's 25 could account for *some* of that difference. Though probably no more than ~0.3W between the CP 26 and 28 @30kph, so certainly not everything the graph is indicating.

I found the article on the test.

https://www.bikeradar.com/...road-tyre-group-test

The challenge tire was a 27mm, so that probably explains why it tested well, likely overinflated relative to the others. The others were 28mm though

They used a track pump to pump them all up, so huge potential error there

Gotta wonder if there's a sizable discrepancy in the measured width of these tires when they're mounted.

looking at those tires tested i just don't believe that test. but if that test is accurate imagine how much faster all the jumbo visma riders would be if they weren't road racing on a dog slow tire ;-)

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Dan Empfield
aka Slowman