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Originally Posted by roflwaffle
I didn't know about RR testing accounting for bearing drag, do you have a link to the equipment/procedure behind this?........
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I don't have a specific link - and I know there are different techniques. I would suggest you look up the SAE procedures. I'm reasonably sure those procedures outline factoring out the bearing loss. Just be aware that they may not specifically delineate what part of the procedure is correction factors and which parts are actual testing.
Quote:
Originally Posted by roflwaffle
......While you don't have any more data, and you have no reason to believe that other tires behave any differently, you also have no reason to believe that other tires don't behave any differently.......
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Actually I do. The important factors in rolling resistance are deflection, the amount of material being deflected, and the properties of the material being deflected.
The load tables are based on the same amount of deflection, so regardless of the tire size, I have a pretty good handle on the deflection.
When it comes to the 2 materials questions - amount and properties - there wouldn't be any fundamental differences that would depend on size. While it is true that as the tire size increases the amount of ply cord increases, those increases also occur within the data range. Plus, there is nothing peculiar that happens in the design of a tire that would distinguish one tire from another that would cause a break in the logic.
The only one that comes to mind is the change from a single ply to a 2 ply - and that change is also included within the data range.
In the end, it becomes extremely important to use the same make and model to assure that the construction is consistent with the tires selected for testing. That is probably where the data set is the weakest. I know there are OE tires in that mix - and I think that accounts for low r[sup]2[/sup] value.
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Originally Posted by roflwaffle
.......... For one, your sample data set is way too small to draw conclusions about a larger population............
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I disagree
Quote:
Originally Posted by roflwaffle
.......... and two, even with the small set that you used to validate your assumption, the author of the data you're using came to a different conclusion, that simple physical characteristics are not enough to predict the RRC..........
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Actually the author didn't highlight ANY conclusions regarding the affect tire size has on RR - and that makes sense given the context. He was contracted by the CEC to get data to help write regulations. As I explained before the tid bit we are discussing was not important for writing regulations. What was important was that there was a difference - and that would complicate writing a regulation.
Quote:
Originally Posted by roflwaffle
.............You just don't have enough data to make any definitive statements about how tires in general behave........
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Again, I disagree
Quote:
Originally Posted by roflwaffle
..........You can assume they behave in a certain way, but that's not scientific.........It's fine as an assumption, but presenting it as anything other than that is not scientific. I'm not saying this to be harsh, just to illustrate the difference between what someone can reasonably assume and what they can't reasonably assume in the scientific sense.
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We have traversed this territory before. I understand your reservations about drawing conclusions on a limited amount of data. I have pointed this out in other situations where I have been on your side of the fence, so I appreciate your sentiment.
Perhaps the best way to say this is: Based on the Smithers data, Bigger is Better.
And unless there are new thoughts, I'm going to discontinue commenting on this as we seem to rehashing the same points.