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Old 05-07-2013, 02:50 AM   #15
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jadatis's Avatar
Join Date: Oct 2012
Posts: 329
@ 96 wideglide
In your Michelin list there, probably no different loadratings are used ( H to D printed at 120 psiH and 65 psi D) wich European system dont do.
To my opinion they dont go lower for TOYO because the calculation becomes to far off for lower pressure and so gives to much more deflection of the tire, then when maximum load and reference pressure on the tire.
This is the goal of all the calculations, but the commonly used calculation in America for C-load and up does not do what it has to do ,and gives at less then 75% of the Pr( the 120 psi for H tires so 75% of that is 90 psi) to much more deflection so they stop for standard load tires there , for Higher loadratings they dare to go lower to that 80 psi because of the lower speed, but then they are already using up the reserves the maximum load has above what they give on the sidewall.
Michelin has to use the TRA calculation in America, but secretly uses for larger trucktires the European power in the universal formula wich lead to lower loadcapacity for the same pressure . In Europe they use the better power but this is still not ideal, and for larger tires they use an even higher power to the idea of an American IR J.C.Daws who did work for them in the past. will give the link to his article about a new way of calculating and comparison with the used systems in America and Europe. over over the 6th doth on his publications page to the conclusions and graphics , you dont have to understand it all.
Gave this link , because there are also other interesting articles, one about Nitrogenium filling. I did not even agree with his system so made my own universal formula , and determined to his article the power and construction load in it ( the part of the maximum load that is carried by the construction of the tire at the given deflection).
What gives me the right to be so pigheaded to use my own formula.
I did some comparison of the used formula's and came to the conclusion that the "Daws"system and the European system and the logical calculation ( what most people think logical = part of the Pr gives part of the maximum load) come that close together and sertainly wont give to high pressure. made a picture of it and will show it here.

For standard load tires in Europe the lowest pressure they give is 60% of the Pr, and that is ok because only then the deflection gets to much more then intended.

But I understand that its hard to not trust official institutes, but the universal formula was introduced in 1928 and they did not have computers then , so had to use much fist rules to make the calculations easy.

So you can use the Michelin list for an American tire with the same maximum load and referencepressure ( Pr = that 120 psi) and if you find one , you will see that it comes to already lower loadcapacity, but better would be to use my lists, they even come to lower loadcapacity. Mayby my calculation is not even perfect, but it comes close to perfect, and takes care that the deflection is the same for lower pressure then for Pr and maxload.
For that reason you might even go back to zero pressure wich is rediculus but sertainly to even 30% of Pr and keeping the same deflection.

The lists I made are meanth to get the loadcapacity's right , and leaves open to use your own reserves.

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