full_mosey wrote:
Hi jadatis;
jadatis wrote:
Once read for ST tires that for higher speed a percentage higher pressure then acording to the lists, and for better handling quality , also a percentage highening up.
If then the new pressure came above maxloadpressure, pressure needed for the maximum load , so reference-pressure, it may not be more then 10 psi.
So my calculation of 44psi + 10% =48,5 psi already has that percentage , wich I mean to remember 2 x 5% , higher then acording to the list,in this case my extra save list, and so stays under the 50+10 psi , and is allowed.
You are also allowed to drive with 60 psi , thoug it would not be good for grip and keeping the screws in the wood of the TT.
You can even stay at normal rubber valves, wich are allowed a cold pressure of 65 to 70 psi ( depending on the brand) with 26 psi extra for higher temperature in the tire, to the mildest american standard.
This 26 psi makes it possible to fill at 65dgr F a pressure of 70 psi and if the inside tire temperature gets boiling point of water ( 100dgr C/200dgrF?) , wich it can incidentialy get by the heat of the brakes, transported trough the rims, the pressure stays below that 96 psi.
High pressure snap in valves wich are alowed for 90 psi maximum cold pressure , or metal valves for over 150 psi.
Yes, I understand, and thank you again for those calculations.
Are your formulas are based on industry standards in Holland? I say that not to challenge, but only to say I must interpret the standard sent to me by Goodyear. As a member of the Tire and Rim Association, Inc., Goodyear is compelled to adhere to those standards in order to use the ST designation.
I base my calcs, the 60psi, on the phrase 'rated maximum load'. If Goodyear had said 'rated minimum load' per the tables, then your calcs would be within the Goodyear PBS #2011-13 which is meant to advise Goodyear dealers.
The issue is not clear yet.
HTH;
John
Got your message at the other topic, so searched this topic, because its not in my list,probably because I did not post here.
My calculations come to lower loadcapacity for the same pressure ,or the other way around to higher pressure for the same load, then the calculation of the TRA for C-load and up, and even then the European ETRTO calculation for all tires.
So is never unsaver then those. What Goodyear gives in their list is lowerloadcapacity for the pressure then mine.
Also I add in my spreadsheet a percentage to the assumed load , wich makes advice pressure even higher.
So my calculations come to higher pressures always so even saver then the official calculations.
To my opinion my calculation takes care that the deflection of the tire stays the same over the whole pressure/loadcapacity range , and the same as when maximum load and reference-pressure on it.
This is the goal of all the calculations is the conclusion I made in time. Also Mr J.C daws goes from the deflection in his article.
For higher speed , for S speedrated normal car tires , referencepressure has to be highenend up with a system depending on the speedcode ( S to Y) to the system of the ETRTO.
This is to give the tire less deflection, because every segment of it deflects and flexes back more in the same time.
But this law of nature also goes for lower speed.
I suspect a ST tire not to be that much different from an LT tire , but is allowed more deflection because of the lower speed of 65m/h instead of often 99m/h.
In the other topic I make clear that to my opinion they did not use this more deflection for the tire there , and calculated the maximum load the same as for an LT tire with same sises and Pr ( referencepressure wich is not the maximum pressure.
Then even with the adding of 10% wich is done for ST for higher speed, it did not come above 50 psi so putting it at 60 is not needed.
If you are interested I can sent you by normal mail a copy of the ETRTO system with calculations for S to W speedrated tires and addings for speed and camber-angle. with this copy my tirepressure-story started.
