terrymorse 

Those "ifs" are doing some pretty heavy lifting.

RChung

That works if your errors are random. That doesn't work if the errors are systematic.

If it were that hard, I wouldn't've been able to do it. But, in general, the smaller the difference you're trying to discern, the more careful you have to be. If you're looking for the difference between, say, a loose jersey and a tight one, you don't need to be that careful at all. That's a pretty noticeable difference.

Eric F 

In the one example of the GP5000, yes. Comparing Vittoria Corsa Speed G+ 2.0 tubeless to the Cosra Speed tubular (the fastest non-tubeless Vittoria on BRR), the 25mm tubeless @ 80psi is faster than the 23mm tubular @ 110psi. If we extrapolate the GP data of ~2W savings for latex vs. butyl, none of the Vittoria clinchers are in the fight,

surak

Except the GP 5K, being a different tire, inflates to a different volume for the same nominal width than the S TR, so it really is comparing apples to oranges.

There actually are some anti-sealant people out there who put in TPU or latex in because they don't want to fuss with sealant. BRR has consistently shown there is a RR penalty for doing this:
https://www.bicyclerollingresistance...-tubes#results
https://www.bicyclerollingresistance...-tubes#average

Also, some pros and copycat amateurs are now using tubeless TT tires in the front or even rear because they are the fastest tires on the market despite being paper-thin, because with sealant inside there isn't as much of a concern about puncturing. Using a tube instead simply wouldn't be wise or result in the same speed -- 0 kph is as slow as it gets when one is pulled over to fix a flat.


From a 2023 Escape Collective article: "many Conti-equipped teams have been using the TT TR since the start of this season for its lower rolling resistance and weight."

terrymorse 

Yeah, I don't think you'll find a clincher that compares favorably to the Vittoria Cross Speed G+. That's a specialized tire that's super thin, suitable for events on good pavement and little else. BRR reports its tread thickness is just 1.8mm -- compare that to the GP5000 TL at 2.8mm, or the Vittoria Corsa G+ 2.0 (open) at 2.6mm.

terrymorse 

Is there really a material difference in internal volume between the clincher and TR? Data from BRR: at 100 psi on a 17.8 mm internal width rim, the two tires are rather similar in measured width, height, and tire thickness.

Seems like searching for a difference, when a meaningful difference isn't there.

PeteHski

The meaningful difference is in flat protection. Tubeless wins that contest by a country mile, which is why I prefer them. Not having to deal with flats at the roadside makes the slight inconvenience of sealant worthwhile. YMMV.

surak

"Rather similar" being 2mm taller measured height on the 5000s. It's already shown that larger volume tires at the same pressure leads to lower measured RR. The 5000 is simply larger.

Seems like trying to ignore any evidence that disproves your assertion because it doesn't fit with your narrative.

terrymorse 

Where has that been shown? I know it has been established for decades that wider tires of the same construction have lower RR at the same pressure, explained simply by the reduced vertical deflection. Not so sure that the same can be said about tire volume.

surak

CRR is affected by contact patch. The larger volume tire at same pressure has a larger contact patch.

asgelle

Final answer?

Eric F 

Valid. I didn't consider thread thickness.

Tubeless is still a winner for me simply due to how they handle most simple punctures. So far, the only issues I've had on the road have been sidewall slash issues that would likely have been the same result with a tubed tire.

Eric F 

Wouldn't the area of the contact patch be the same, and just vary in width and length depending on tire size?

terrymorse 

Want to bet on that?

surak

OK, I messed that up, I should have written that the higher volume tire should have a wider contact patch, not larger. BRR's measured casing width of the GP 5K is also 2mm wider than than the S TR.

This all assumes that the tire construction is the same between the two models, as that also affects the contact patch shape. That seems highly unlikely, which is another reason why comparing two different tire models to try to prove that tubed tires are just as fast as tubeless is meaningless.

Eric F 

Why do we need to assume tire construction is the same? TL and TT tires are built differently, and those differences affect Crr. For the purposes of discussion, "fast" is about lower Crr.

surak

I was being rhetorical. If all we care about is what's faster, why compare the 5k to the S TR? Already shown that BRR measures higher RR with tubes in a tubeless tire. If you agree that the S TR is built differently than the tubed 5k, why is showing the 5k having lower RR than the S TR any proof that tubed tires are faster as tubeless?

terrymorse 

I see that, 66 mm vs 64 mm, an increase of 3% of the tire cross section circumference, or about a 6% of the tire volume.

Meaningless to whom? I'll continue to use my clincher + tube setup, safe in the knowledge that my tubed tire setup is fast. The only thing that truly matters is results.

I'll continue pushing back against the "common wisdom" that tubeless is faster, because it often is not.

Eric F 

I'm still hopeful that BRR (or someone) develops tires tests for non-perfect surfaces. I'm really curious to see power loss comparison data for how tires of different sizes/pressures/structures react to different surface textures.

EDIT: Since this ^^^ post, I found out that BRR's test drum is not smooth, as I had assumed. It's made from diamond plate in an attempt to approximate the imperfect conditions of real roads.

Maelochs

This. Weight was a super-effective marketing tool because is is easily quantifiable, and when people started riding they rode heavier bikes, and as bikes increased in cost, thy weighed less ... therefore lighter was better. Marketers could tout tiny weight savings over last year's model, or "other bikes in class," and gain customers.

In a similar way, when "stiffness" became a thing, manufacturers would claim that This Year's Model was ".000667 percent stiffer laterally, for better power transfer, and .008834 percent more compliant vertically for a more comfortable ride."

Now that aero has been shown to trump all else, every frame is ridiculously stiff, and since wider, softer tires and both faster and more comfortable, a lot of people don't mind buying stiff frames.

This also. "Marginal gains" only really matter at all if a rider thinks they do. .000673 percent more aero means zero to me, and the days when shaving every gram was affordable have passed for me. I can just ride my bikes and i don't care.

RChung

If only there were some way to assess Crr (and CdA) with field tests on real roads.

(That said, measuring Crr is one of those things where you need to be careful with the measurements).

mikeoverly

When you can measure a difference repeatedly over a consistent course I'd say you have a data point as an amatuer. Pros don't seem to care a ton about a half-pound here or there or many of the other things we duffers obsess over. For a group ride it's a lot more about your personal capability and where you are in the pack.

rydabent

Light weight high priced bikes are of a concern to those that race. For the rest of us a fairly good quality bike will serve us just fine.

zymphad

Agreed. Meanwhile people are discussing the value in saving 2 watts riding tubeless vs tube above you

PeteHski

Sometimes bland mediocrity is not quite enough, especially when it comes to our main hobbies and interests. There are thousands of riders out there who don’t race, but still enjoy riding high quality race bikes. It has nothing to do with what they “need”.