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PostPosted: Tue Mar 11, 2014 9:31 pm 
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Hi,

Quote:
This is pretty much what I'm asking. Is there anything inherent in the handmade procedure that a vulcanised tyre can not achieve? Got conflicting opinions so far. And I don't mean exceeding just in any one characteristic, but with the goal of balancing grip, puncture protection and rolling resistance.


The main difference between the two is that the handmade procedure allows you to use any tread available, natural rubber (produced from latex) or synthetic. All rubber is vulcanised or it wouldn't be of any practical use for a tyre BTW.
The vulcanisation process we are referring to is the process that allows two different compounds to become permanently attached. I.e. multi-compound tyres where a different rubber is used for tread and casing.
In order to achieve this a chemical process is re-used (vulcanisation) so the various rubber compounds become an seamless one.
This is the most common procedure for industrially made tyres. Now, what sets this apart is that the rubber (synthetic in most cases nowadays) is vulcanised several times and this makes it less supple, less flexible compared to natural rubber which was only vulcanised once.
Now I'm far from being a chemical engineer but the trick is of course to formulate a rubber compound that remains flexible enough, does not cut easily, offers good grip and so on after it has been vulcanised onto the casing.
A casing that will already contain a rubber layer for the tread to vulcanise on to.

Traditional handmade tyres* (mostly tubulars) use different procedures in that the entire casing is coated in several layers of latex (which is of course not vulcanized) upon which the tread is glued. You can't (to the best of my knowledge) vulcanise onto a latex layer directly.
Now, from the description of both procedures it becomes clear that the handmade tyre will maintain a far higher amount of flexibility since the sidewalls are merely protected by latex and the least flexible part (assuming no anti-puncture belt) is the central tread.

So, logically it will take one hell of a good compound to beat the handmade tyre. Not impossible but not very obvious to achieve.
One could easily go on for days like this but I'll stop the rant right here.

*There are several ways to go about this but nowadays the procedure is grosso modo as described above.

Hope this helps, ;)

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Posted: Tue Mar 11, 2014 9:31 pm 


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PostPosted: Tue Mar 11, 2014 10:44 pm 
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uraqt wrote:
@ bombertodd "The first Evo CX didn't have great grip in the wet" Compared to what?

I think Vittoria is the "cream of the crop" : )

IME The open pro has always been better than other brands matching releases. It's only limit is wear for the heavy guys. Never a side wall cut and much better in the wet than any other brand.


It didn't have great grip in the wet compared to the second and third versions. I still feel the first Evo CX was a great tire overall. Although the first version still had better grip than some other tires I've ridden such as GP4000s.

I'd agree that Vittoria is is one of, if not, the cream of the crop. I really like my Veloflex Corsa's too.


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PostPosted: Wed Mar 12, 2014 2:45 am 
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wassertreter wrote:
Call my a tyre nerd, but wasn't the conventional wisdom that handglued tyres were the best, and I think Jan Heine has been quoted saying the same here in this thread? Now in his blog entry about the Compass tyres, Heine says vulcanized was better, because the tread was not under tension when the tyre is inflated. I can see how a tension-free tread helps prevents (or at least limiting) cuts.


To get the tread "stress free" when inflated, wouldn't the tread need to be attached with the tire inflated? On a hand-glued tubular that is theoretically possible, but I can't imagine it happening with any clincher or vulcanized tubular.

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PostPosted: Sat Dec 20, 2014 10:55 pm 
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Interesting topic, that I happened to land on just today. There are some comments that may benefit from further explanation. For example, the pendulum roller to measure the rolling resistance coefficient of a tire (see Youtube link in post #13 on page 1 of this topic ; as a novice I'm not allowed to post links). I didn't see the theory of the roller explained. The scientific background is in the paper of Barry J. Hill, Measurement of the Rolling Resistance using an Excentrically Weighted Oscillating Wheel, in Surface Characteristics of Roadways, ASTM STP 1031, 1990, pp 497-504 or in the paper of Wang, Macedo and Reid, A method for quantifying the rolling resistance of bicycle tires, in Engineering of Sport 5, Volume 2, 2004, p. 132 .

In my opinion, the main observable to focus on is not the time-to-standstill but the total distance that the wheels cover rolling back and forth. Measuring the amplitude or angles at several turning points and doing an reasonable regression to zero amplitude would directly yield the Crr value.
It has several advantages over a coasting-down method, such as requiring only a very short track, about half of the wheel circumference, and not requiring a long and perfectly flat surface. The vehicle is not only able to measure the Crr of tires, wide and narrow at variable pressure, but also the effect on Crr of a rough surface, like chip-sealed asphalt. However, in the end it dances on a very short track, so measuring a cobblestone surface might be problematic.


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PostPosted: Sun Dec 21, 2014 1:30 am 
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Bit OT, but seeing topic 1st thought was " how much it takes to see someone "defending" Continental tire (?)" .

7 posts only :mrgreen: :shock:

( if your thoughts -as mine- lead to conclusion that Shimano/Conti trendsetting is real and exist on this forum, in more non-subtle form than it should, you are naturally wrong… or not :thumbup: )

It start to be pathetic…


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Any test of rr made has certain margin of reliabilty caused mainly by procedure( lets think for a while that someone really want to make test without any influence from manufacturers/ dealers / advertisiers - hard to believe, but imagine that can happened ) . To measure REAL crr values it would take far more time & effort & will generate cost of it being comercially ( for magazine ) unjustified. And what even worse , results ( difference between models ) can be very surprising .

factors which should be considered to receive relaible results :

1. closed track with defined 3 types of tarmac : from glass-flat to harsh, surface dry + wet .
2. air temperature, tests made in 3 different ( 10-20- 30*C for example )
3. air pressure : lets say 1013HPa, 980 and 1045
4. height ( over the sea level ) : 500, 1000, 1500
5. humidity : low , mid, dry
6. load ( imaginable rider + bike weight : 70-80-90kg f.e. )
7. tire temperature ( cold and warmed up )
8. rim variability ( elasticity , profile width )
9. front/ rear wheel load ( different weight balance for tt/ tri / road )
10. Various tire pressures for all tests for certain tire with factor of butyl & latex tube
11. resistance on straight and cornering
12. same downhill & uphill ( weight load variable )
13. season ( air density ) & weather
14. what was used to pump tire : air, Co2, N … (?)
15. high and low cadence ( different load- rear tire bend on stroke )

Sounds - at least - crazy :) But let's be "precise" - to the end . with or without any sense of it .

list can be very long… no one will make it . ever. It cost money. Not even 1 manufacturer will agree to share so enormous costs of that kind of test, not knowing result :)

But seriously :
Just maybe it doesn't have any sense ? I mean in real life & on certain level of product. For magazines and manufacturers tests do have sense ;) specially these showing Conti GP4000S2 superiority :mrgreen:



I like to watch what use athletes which are good enough to use what they want instaead of what they are paid for. My observations ( and small experience ) are way different from any tests results and "common" opinions. By common I mean adverts ( payed and hidden ) , tests results & Co.

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PostPosted: Mon Dec 22, 2014 4:15 pm 
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Nice post.

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PostPosted: Tue Dec 23, 2014 10:09 am 
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Stormur, it's a nice wish list, but you make it sound more complicated than it needs to be, and thus ensure that noone will ever do such a perfect study (you list 15 factors, 10 with 3 levels and 5 with 2 levels, that's more than a million permutations). The point is not to quantify everything that might influence rolling resistance, but to determine if tire A is better than tire B (in usual riding conditions, or averaged over common conditions). Even a single comparison under one set of conditions is a useful datapoint. Sure, air humidity (e.g.) may influence rolling resistance, but would it act differently on tire A than on tire B and thus change their ranking? That would take some strong assumptions. Not saying that it's impossible, but then it would be up to the person who makes these assumptions to go out and test them. I'm all in favor of people like Heine to do even limited independent testing; it's better than no data at all, or than promotional pseudo-data.


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PostPosted: Tue Dec 23, 2014 10:23 am 
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So much of riding is the tyre moving side to side. Both by steering, turning and also by the road surface. The centre of the tyre is not the only part brought into play - but the most obvious.
I believe the glue job on a tubular makes a very big difference.


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PostPosted: Wed Dec 24, 2014 4:11 pm 
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Basilic is right--from an engineering perspective, Stormur, you're overcomplicating the issue. There's an important distinction between "all the variables I can think of" and "all of the variables that matter."

-----------------------------
TL;DR: Rolling resistance tests like Tom Anhalt's and the pendulum method are very useful; the variables they neglect don't matter much or at all.
-----------------------------

Rolling resistance is well understood within the engineering world but things are different in the bike-technical-enthusiast world. In bias-ply tires--and all bike tires are bias-ply, even the Maxxis Radiale*-- most of the rolling resistance comes from the interlaminar shear strains between the plies. The elastomer (rubber, latex, whatever) turns these strains into heat via hysteresis. Cotton-cased tubular tires typically have very little latex between the casing layers, so they tend to have low rolling resistance.

(Random side note: high-TPI tires don't have low rolling resistance because they're supple--suppleness is a side effect. They have low rolling resistance largely because there's less free volume between the threads to hold high-hysteresis latex or rubber).

Radial tires do not experience significant interlaminar shear, so their casings lose less energy to hysteresis and therefore have much lower rolling resistance than a bias-ply tire of comparable construction.

OK, on to Stormur's variables. Some of the things he lists matter, but many do not and some are redundant.

stormur wrote:
Any test of rr made has certain margin of reliabilty caused mainly by procedure

This is true of every experiment ever conducted. It's something to keep in mind, but it's not a problem at all.

stormur wrote:
To measure REAL crr values it would take far more time & effort & will generate cost of it being comercially ( for magazine ) unjustified. And what even worse , results ( difference between models ) can be very surprising .

Well, this all depends on what you mean by "REAL CRR values." Getting the absolute right value isn't really of interest; no one cares if all your values for power consumption are high by 0.01 Watts. What's really of interest is relative measurements, and these are pretty easy to get with a high degree of repeatability. Both Tom Anhalt's tests and the pendulum method are pretty rigorous and seem to generate similar results for the same tire models.

In other words, you can get very good results quite cheaply. This comes down to the distinction between accuracy and precision. Tom Anhalt's tests and the pendulum tests are quite precise, and, for rolling resistance, if you have good precision (relative measurements between tires) then accuracy (exact wattage consumed by a given tire) isn't very important. Here's more info: http://en.wikipedia.org/wiki/Accuracy_and_precision




stormur wrote:
1. closed track with defined 3 types of tarmac : from glass-flat to harsh, surface dry + wet .

Texture doesn't matter. The value of rolling resistance is higher on a rough surface, but if tire A is faster than tire B on smooth surface, it will be faster than tire B on a bumpy road as well. This is why it's fine to use a smooth steel drum and apply the results to real-world roads: you're just trying to measure how much energy is absorbed for a given amount of deflection. Again, all that matters is relative values between tires.

I know Wheel Energy in Finland sometimes tests with textured surfaces. But I haven't seen any data that show that, as above, the difference between two tires changes depending on surface texture. If Wheel Energy (or anyone else) have those data for bike tires, I'd love to see them. Here's a link to some of their results:
http://velonews.competitor.com/2014/12/ ... nce_355085

Relative values between tires might change depending on wet or dry conditions. It might be worth investigating if you were running a pro team that focused on the classics (which tend to be wet), but this is a second-order effect.

stormur wrote:
2. air temperature, tests made in 3 different ( 10-20- 30*C for example )

This might matter (a little) in extreme temperatures. Hysteresis in elastomers can vary nonlinearly with temperature. But between 10-35 degrees C, relative measurements should be pretty similar. Again, a pro team racing classics (which tend to be cold) might want to check this out. This is also a second-order effect.

stormur wrote:
3. air pressure : lets say 1013HPa, 980 and 1045

I think you're referring to ambient barometric pressure. This doesn't matter at all. What matters is the gage pressure of the tire (what it's pumped to). A tire pumped to 8.3 bar (~120 psi) over ambient pressure is 8.3 bar above ambient pressure no matter what that ambient pressure value is.

stormur wrote:
4. height ( over the sea level ) : 500, 1000, 1500

This is essentially the same variable as #3, and it doesn't matter for the same reasons.

stormur wrote:
5. humidity : low , mid, dry

Nope, humidity doesn't matter. A cotton casing inadequately coated in latex *might* absorb some water from the atmosphere, but any change in CRR values would be swamped by moisture retained the last time it was ridden in the rain. This is a third-order effect at best.

stormur wrote:
6. load ( imaginable rider + bike weight : 70-80-90kg f.e. )


This doesn't matter at all. In fact, the very concept of a coefficient of rolling resistance requires that energy dissipated be directly proportional to the weight on the wheel. If you think "load" is a nonlinear variable, then you've rejected the very concept of a CRR.

stormur wrote:
7. tire temperature ( cold and warmed up )

This is the same as #2. Tires do warm up when you ride them, but by a tiny amount. They dump so much heat to the wind that tire operating temperature doesn't change very much in the course of a ride. If anyone out there has an infrared thermometer and can provide data to contradict me, I'd love to know about it. (Tire temperature matters a lot for auto racing, but that's a different kettle of thermodynamic fish).

stormur wrote:
8. rim variability ( elasticity , profile width )

This is also irrelevant in practice. I'm not sure you realize this, but what you're suggesting is that it's somehow plausible that a GP4000S II will be significantly faster than a Pro Race 4 on a Kinlin rim but slower than a Pro Race 4 on a Hed Belgium rim.

If rolling resistance is a mysterious, semi-magical phenomenon to someone, then that suggestion might seem true. But even a rough understanding of why some tires roll faster than others will make it clear that a tire that rolls faster on a Kinlin rim will also roll faster on a Hed Belgium rim. It may be true that a Pro Race 4 on a Belgium rim is faster than a GP4000S II on a narrower Kinlin rim. But for a given rim, the relative CRR values will hold. E.g., if a Pro Race 4 has 7% more rolling resistance than a GP4000S II on a Kinlin rim, it will also have ~7% more rolling resistance when both tires are mounted to a Hed Belgium rim.

I'm not making fun of anyone or suggesting that they're ill-informed; I'm just trying to de-mystify the physical phenomena involved.

stormur wrote:
9. front/ rear wheel load ( different weight balance for tt/ tri / road )

Nope. Irrelevant and redundant; see #6

stormur wrote:
10. Various tire pressures for all tests for certain tire with factor of butyl & latex tube

Also irrelevant and redundant; see # 3. Butyl vs. latex matters a lot, but we only know that because it's been well established with the very tests you decry as inadequate.

stormur wrote:
11. resistance on straight and cornering

Eh, in theory these could be different. But very few people are getting dropped in crits because their rolling resistance goes through the roof when they lean over for a corner. At any rate, this is easy to test using a pendulum rig with cambered wheels.

stormur wrote:
12. same downhill & uphill ( weight load variable )

Irrelevant and redundant; see (again) # 6. Do you really think all of these incarnations of the same variable are somehow different?

stormur wrote:
13. season ( air density ) & weather

Irrelevant (#3) and redundant (#2, #3, #5, #7 ...)

stormur wrote:
14. what was used to pump tire : air, Co2, N … (?)

This is a third order effect at best. What you're really talking about here is viscous damping of the gas used to inflate the tire. In theory, there are tiny differences, but in practice, these are swamped by all of the first-order variables that do matter, such as inflation pressure, section width, casing construction, etc.

stormur wrote:
15. high and low cadence ( different load- rear tire bend on stroke )

This doesn't matter. If your cadence happened to match the resonant frequency of the bike/rider/tire system, you'd be bunnyhopping down the road. Besides, we've already established a direct relationship between load and rolling resistance--there's even a coefficient that describes this relationship.

stormur wrote:
Sounds - at least - crazy :) But let's be "precise" - to the end . with or without any sense of it .

It doesn't sound crazy, but it does sound like a non-scientist's view of what science might be like. There's no shame in this, of course. Also, in the most technical sense, your list doesn't address precision; it addresses accuracy. But again, this is a subtle distinction that's lost on even some scientists and engineers.

stormur wrote:
list can be very long… no one will make it . ever. It cost money. Not even 1 manufacturer will agree to share so enormous costs of that kind of test, not knowing result :)

If you made a list of everything that has an effect on rolling resistance, it wouldn't just be long: it would be infinite. But the list of variables that matter for a useful test is quite short. Both the pendulum test and Tom Anhalt's tests on BikeTechReview capture them well. Anyone, including manufacturers, can perform tests like these at minimal cost. Including some of the second- and third-order variables mentioned above would increase cost a little without much benefit.

I'm an engineer (as you've probably guessed) and engineering is often described as "applied science." This is a useful description. A big part of applied science is knowing which parts of the science one should apply and which parts don't matter much. If you leave out something important, your results will be wrong. If you include things that aren't important, you get bogged down in the quagmire of variables Stormur seems to dread.

But if you can discern the variables that (a) are measurable and (b) matter, you can strike the right balance. One might think of this as a 90/10 rule: 90% of your result quality comes from 10% of the variables. Things like wind drag, rolling resistance, "speed wobble" and frame/crank/component flex are quantifiable and quite accessible to physicists and engineers. If they weren't--if these things were as unknowable as some people seem to believe--we'd be living in a permanent stone age.

Cheers,

Jason

P.S. I seem to have written a bit of a dissertation here. There's a reason for that. When I was a junior racer back in the mid-eighties and early nineties, I wondered about this stuff all the time. No one I knew--not teammates, not national-level coaches, not even the framebuilders I talked to--had any idea about why bicycles work. One well-respected coach warned me that my radially-laced 28-hole front wheel would "probably fold up in a corner" under my crushing 130-pound weight.

I was desperate in those pre-internet days for any informed thoughts on these subjects, and I would have killed for Jobst Brandt's Usenet posts (or this forum) back then. These things are eminently knowable and understandable, and I find that exhilarating.

I became an engineer because I was tired of not knowing whether a stiff frame was more efficient than a flexy one (it's not, really) or whether aero spokes build a stiffer wheel than butted spokes (they don't; the only thing that matters is spoke cross-sectional area). I didn't write this to wag my finger at anyone or make them feel dumb. I write posts like this for the contemporary incarnation of the 13-year-old kid I used to be. So yeah, I'm flying my freak flag high.


* Panaracer made a true radial bike tire in the '80s, sold as OEM tires on some Miyata models. Allegedly, they felt odd and squirmy, as though they were underinflated even at full pressure. This is because radial tires lack torsional stiffness, which bias-ply tires have in spades. The radials on your car have a steel belt not to protect against punctures but to provide torsional stiffness. cf.: http://www.bikeforums.net/classic-vinta ... tires.html


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PostPosted: Wed Dec 24, 2014 5:47 pm 
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youngs_modulus wrote:
I was desperate in those pre-internet days for any informed thoughts on these subjects, and I would have killed for Jobst Brandt's Usenet posts (or this forum) back then. These things are eminently knowable and understandable, and I find that exhilarating.

I didn't write this to wag my finger at anyone or make them feel dumb. I write posts like this for the contemporary incarnation of the 13-year-old kid I used to be. So yeah, I'm flying my freak flag high...

* Panaracer made a true radial bike tire in the '80s, sold as OEM tires on some Miyata models. Allegedly, they felt odd and squirmy, as though they were underinflated even at full pressure. This is because radial tires lack torsional stiffness, which bias-ply tires have in spades. The radials on your car have a steel belt not to protect against punctures but to provide torsional stiffness. cf.: http://www.bikeforums.net/classic-vinta ... tires.html


@youngs_modulus, Great post man! Informative and complete, and that was a fascinating bit about the Panaracer radial tires. I had heard anecdotal info about radials not being used because of the lack of torsional stiffness, but didn't know Panaracer had actually brought a model to market.

Also, regarding the writing for the next 13yr old kid asking these questions...so true, and true for so many of us! :thumbup:


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PostPosted: Wed Dec 24, 2014 9:58 pm 
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Hey, thanks! I'm glad you liked it.

Cheers,

Jason


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PostPosted: Wed Dec 24, 2014 10:24 pm 
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Yeah, great post and a good read too.

I had the Victoria radiale tyres and they were fine but probably not truly radial either.


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PostPosted: Wed Dec 24, 2014 11:40 pm 
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youngs_modulus- thanks for the long post.

The early radial motorcycle tires tended to feel squirmy. They did not become successful until they fixed that by making the sidewalls shorter and stiffer (and the wheels wider). I'm sure bicycle tire designers know all about that (and in many cases are in companies that also make motorcycle tires) so there must be a reason why that solution does not work for radial bike tires.


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PostPosted: Thu Dec 25, 2014 12:14 am 
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:thumbup: Awesome write up youngs_modulus!

I think this sport/industry is rife with pseudoscience that gets repeated ad nauseum (see commonly held beliefs about rotational weight, "pulling up" while pedaling, relative importance of stiffness, frame/wheel comfort, aerodynamics, etc.) and for some reason people cling to those beliefs and tend to hand-wave away anything that so inconveniently challenges their current beliefs (which makes you understand why scientific policy moves so slowly). Fortunately, thanks to posts like yours, this is is ever so slowly starting to crumble as more and more data is released about the various factors that come into play while riding. As a non-engineer, love it when it's stated in laymen's terms, so thank you!


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PostPosted: Thu Dec 25, 2014 5:53 am 
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That's very interesting Jason, I emailed Jan from the bicycle quarterly tests and they don't believe that the rollers are a good model for rolling resistance... Instead they believe you should conduct these tests on an outdoor track :?

I asked about using rollers to test the crr of tyres because it should be able to produce reliable results, but Jan doesn't believe its a valid model, citing that it penalises supple casings.

Quote:
In your case, you have the opposite problem: You use a model to replicate real-world conditions. Any model needs to be validated to ensure that it does replicate the real world. We tried to replicate the roller as a model, and we couldn't. Some tires that scored great on the roller (Michelin Pro2 Race) scored only average on real roads. So for now, it appears that the model is lacking.

If you plan to use the model of a small-diameter drum (which will penalize tires with supple casings), then you really need to validate that model first.

Basically, the TOUR tests on Continental's steel rollers showed the Pro2 Race being way faster than the Conti Ultra Gator Skin. In our real-road tests, the two had the same speed. That indicates that the roller tests aren't very useful


Or could it indicate that their "real world" tests aren't very useful?

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