Kapusta

I've responded to this particular article many times over the years. I will try to find my response so I do not have to re-type.

But three things for now:

1- The chart you refer to is a sample size of one. One tire.

2- look at the 5th chart (the one with the 25mm Continental GP4000s II tires). The roller drum data is different that the real world data (even the brand new asphalt)

3- The point of that article and the tests shown were not to validate the roller drum data as a reliably accurate for real world values, and they do not claim it does.

asgelle

Which is why I wrote you can infer the rest.

Kapusta

Actually, what I have confirmed to myself is that the data from BRR.com for two tires I have actually owned is very different from how they worked on the road.

Also, take a look at the link to the German magazine test linked to earlier that contradicts the drum test for the Bon Jon Pass.

Kapusta

No, actually you can't infer the rest with a sample size of one.

Plus, as I said, look at the chart down farther showing results for the 25mm Continental GP4000s II.

WhyFi

Show me.

WhyFi

I mean, it's besides the point, but why not?

asgelle

It’s not a sample size of one. It’s validating the model to translate from roller data to road Crr. While that might not be ideal, since the model has no tire dependent parameters, it’s strongly indicative. Put that together with several experts all saying the correlation holds and I’d say it’s convincing.

Kapusta

Yes, it is beside the point. We agree an something

WhyFi

It's not beside the point that you don't believe anything that you didn't confirm yourself, so... I don't believe you.

Kapusta

A sample size of one does not validate anything.

Are you purposely avoiding looking at the 5th chart (the one with the 25mm Continental GP4000s II tires)? The roller drum data is different from the real world data (even the brand new asphalt). So for one tire the drum data is the same as smooth asphalt and another tire it is different on smooth asphalt, and then VERY different on rougher asphalt.

How can this possibly be interpreted as validating drum data as a accurate predictor of real world results?

The authors make several conclusions in this article. What you are claiming is not one of them.

Kapusta

Ask literally anybody who has owned a Bon Jon Pass if they think that data on BRR for that tire makes sense.

Also, take a look at this: https://www.renehersecycles.com/test...res-isnt-easy/ The German test also has issues, but when you look at the tires the Bon Jon Pass is hanging with, the results are very, very different from the roller drum tests in terms for where the BJP ranks.

And heck, just follow the discussion I am having with asgelle about that Silca article. Look at the result in the two plots we are talking about (well, I am talking about both, he is ignoring the second). Contrary to proving that the roller drum tests can be accurately used for comparisons, it actually shows the limitations.

asgelle

Are being purposely obtuse? The second plot applies a model to translate roller data to road. The sample size is not one, but three for number of data points taken on the road. The lower plot does not apply the model to the roller data and just shows the roller and road results as is.

WhyFi

This whole off-shoot of a conversation is about relative performance of tires as predicted by roller data. How is the 5th chart contradicting this? It only shows the impedance break point that was mentioned in the RChung quote that I'd copied.

WhyFi

It's also worth noting that this test, which you claim invalidates RChung's statement, was performed with RChung's method -

"We decided to turn this opportunity into a tire pressure and Crr test using the Chung Method to determine Crr from field testing. ​​​​​​"

So yeah, I guess you're right - totally shouldn't take that guy at his word.
​​​​​​​

Kapusta

You are taking a bunch of disparate information and molding into a conclusion that none of it supports.

WhyFi

Lol. No - looking through your posts, it's clear that you don't understand what's being discussed. We're not talking about roller drum accurately predicting rolling resistance, we're talking about roller drums predicting relative rolling resistance performance. IOW, if Tire A performs better on the rollers than Tire B, you can expect A to perform better than B in real life, too (unless they were very close to begin with and their impedance break points were slightly different and the tests were performed under conditions that would favor the break point of B, in which case the two [already close] results might be inverted).

asgelle

and to go one step further, when asked for proof of this, I posted a link to Tom Anhalt’s results showing roller data can be translated to road without any tire-dependent parameters implying that below the break point, the relative position of tires is the same on road as rollers.

As to the Heine write up, it’s intriguing, but I don’t know how much weight to put behind someone saying a test in which his product performed poorly is flawed.

Kapusta

Are we talking about the same graph?

From the description, the roller data (dark blue with data points) is there along with the predicted CRR (light blue line). And the real world data. The authors even note there surprise at how close the real world data was to the ROLLER DATA.

And yes, this is a sample size of ONE TIRE. They even specify the tire (23mm Vittoria). This shows the roller data accurately predicting the RR of ONE TIRE.

You mention three data points taken for the road. Sounds logical, but where is this described? And where is it specifying that the roller data is being presented differently here than in the chart below. Is there a "methods" link that I have missed?

And here is the fifth chart:


Again it shown the roller data (dark blue with data points) along with what I think is the predicted CRR (it is a light blue line but not labeled). Where is it specified that the roller data is being presented differently than for the 23mm Vittoria?

If the debate here is whether drum tests can be a reliable predictor of how tires will rank, I really don't get why we are arguing over this study. It does not address that question. It never asks it (except in the background describing a single test that led to a surprising conclusion that led to the study described in the article), and it never mentions any conclusion regarding it. And the only relevant info I see to he question does nothing to support it (unless you consider the validation of a single tire to be meaningful support). If anything the differences between the two graphs shown casts some doubts... though I am still open to an explanation of how you know from that article that the roller data is presented differently in the two graphs.... if that is the case, I will cede that the second graph does is not counter-indicative to the conclusion of the earlier graph.

Kapusta

Forget his write up, just look at the results of the other test.

And again, ask anybody who has spent time an a Bon Jon Pass. The BRR.com results don't make sense.

Kapusta

Actaully, I was talking about comparisons. That is why I brought up the difference between the second and fifth graphs. Graph shows the real world data for a 23mm Vittoria on smooth pavement very consistent with the roller data (in fact that authors even mentioned that they were surprised by this) but the other (25mm Continental GP4000s II at on different surfaces) shows the drum and real world data differing from each other for a different tire. If you want to be able to use the drum results for relative comparisons, then the differential between drum test and real world needs to be the same.

But more on the 5th graph of the 25mm Continental: there is a differential between the roller drum test and the various road surfaces. Your assumption is that this differential for the different surfaces will be consistent across all types of tires. THIS is what I have yet to see anyone demonstrate.

You are quoting RChung as saying he has demonstrated that this assumption is valid, but you are not specifying what context he is working in. Is he referring to all types and sizes of tires? Everything from superlight 23s to 42mm gravel tires? Differing road conditions? Or is he focusing on something more specific? This is why I said that without knowing more about what he is testing, you can't assume it applies to all tires.

Kapusta

OK, I have spent way more time on this than I ever meant to. If you want to have full faith in drum tests for all tires, have at, and enjoy.

More RH tires for the rest of us

WhyFi

Oh, good gravy - is that what this is all about? You're an acolyte and the tests don't heap enough praise your deity? If the relative rankings don't include the superiority of your rover tires bounding over lunar craters, it must be fundamentally flawed?

I'm a big believer in (relatively) wide and (relatively) low pressure - I'm ~180 lbs and ride 28mm tires at ~60psi on wide rims. I understand suspension losses and appreciate the comfort of lower pressure on ****ty roads, yadda, yadda. But, for every individual, there comes a point where more of a good thing involves too big of a trade-off. I like the feel of a spritely bike - I like to change speed and direction. I spent several thousand miles with supple, oversized 30mm tires. While they were a magic carpet ride, they felt too sluggish for me when I transitioned to more punchy group rides. Horses for courses. So, yes - if your "real world" conditions involves riding on rumble strips, by all means, you can have my share of RH tires.

Kapusta

Well that is one way to handle a technological debate. Not my cup of tea, but if it works for you.....

RChung

Yikes.

Kapusta

Since you have been quoted here, I was going to reach out to you to get some clarification:

How wide a range of tires did you find the roller data to match up consistently with the real world data (at least in terms of ranking)? Does this include touring and gravel tires? Different surfaces?

I'm also happy just to follow a link if you point me in the right direction.

Please know I am not questioning what you are doing or your results, just trying to understand what is being covered.

This is exactly the info I've been hoping to find for several years now.

Thanks in advance.