i think every time someone comes up with some figures they add a few more PSI just to make sure.. this starts with tyre manufacturers who almost certainly work to at least a 10& safety margin.. then along comes someone else who takes the figures that already have a built in 10% margin and then adds another 10% just to be sure..
at the end of this along comes the owner who more likely than not adds their own 10% to the already over inflated (pun intended) figures with the end result of a whole bunch of tyres being blown up harder than they should or need to be..
i arrive at my own conclusions which is something i often do.. i do keep a careful check on my tyre temperatures.. as long as they dont run too hot i am happy enough i am not running them too soft..
Inside tyre temp is about 45degrC/112degr F when driving about 60m/h on normal day temperature.
So if you read that , the tyres must be save is my carefull conclusion.
When severe braking or sunshine on tire the inside tire temp can rise to 100degrC/212degr F , so a valve importer wrote me. At that moment the pressure will rise so lesser deflection , so lesser heat production.
So dont be alarmed if you read that temp on your TMPS.
If you know then that you have been serverely braking, thats the cource.
But my conclusion is that if you would realy drive with given maximum load on a tyre AT pressure tyre maker gives, and your speed is over 99m/160 km/h , wich is reference speed they calculate it all for, you will damage your tires , and there is no , or yust little reserve .
The reserve is created by calculating it for 99m/h and only driving 75m/h wich gives , as I have found out, 4 LI steps more maxload = 12% more maxload.
But again I calculate a highest pressure at wich comfort and gripp is still acceptable so leaves as much possible reserve for things like.
Pressure loss in time.
Misreadings of pressure ( by your selfes of inacurate device)
Misyudging of real weight.
Unequall load R/L.
etc
etc
In time also misyudging by tyre- and car-makers has happened.
One is the old 10% rule. For older caravans normal car tyres where placed with system 10% extra pressure gives 10% extra maximum load if you only drive 100km/62m/h maximum. Many blowing tyres because real load went even over this new maxload or speed higher.
Also in America ST-tires wich are given maxload for 65m/104km/h, wich is about 18% higher then a Q speedrate tyre ( 99m/h).
Also many blowing tyres because calculate to the edges.
That these 2 systems are not in line with each other must be saying something, to my conclusion that at least one of the systems is to exagerated.
purely my own theory on this one but i think the whole thing about caravan tyres blowing out or suffering side wall failure is a myth..
they dont blow out what happens is far more simple.. the tyre gets a normal puncture (even new ones can get these) the driver unlike a car driver is totally oblivious to all this..
the pressure slowly goes down the tyre gets hot and in the end delaminates.. when this happens the driver stops and assumes (wrongly in my opinion) that the tyre has suddenly blown out without warning.. so does anyone else that views the wreckage.. he he
people will say they could not keep driving along with a semi flat caravan or trailer tyre.. i am pretty sure they could and most likely would.. i think delamination and a tyre flying apart is the end result of most trailer punctures.. the same applies to lorries as well..
the whole exploding myth game is perpetuated by clueless safety experts and the people that make money from selling new tyres..
Trog that theory is bang on only truck or tyres running with over 100psi blowout, car and van deflate be it slow or fast, the casing damage is caused by the rim cutting the tyre to shreds as you drive on it or as you bring the vehicle to a stop, 30psi or around that just make a large hiss as the burst, you would not hear it go in the car.
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Topic: tyre pressure
