Rawalpindi-Balakot-shogran-naran-lulusar honda city 2010

[ehalin]

Thank you very much for clarifying the Physics involved in tyre pressure and also explaining the practical experiments. But have you ever checked the pressure with and without load in tyres? I think you have never done that. A truck tyre after loading even 10 tonnes of goods does not change its pressure. Tyre pressure changes only when more air is pushed or reduced or its temperature changes. This is coming from a famous physics formula which says that P x V / T (for a properly inflated tyre variation in V is negligible) of a compressible fluid remains always constant. Actually when you load a tyre its contact area with the ground increases and since pressure is always mentioned in pounds per square inch which being constant at the time of application; the increase in sq inches of contact area with the ground allows it to carry more load i.e., more total force exerted by the vehicle to the ground.
When load is put on the tyre. There is some flex in the tyre wall. More load and there is more flexing. This continuous flexing and relaxing of tyre side walls at high speeds (when the tyres are under inflated or vice versa the vehicle is overloaded) tend to overheat the tyre which is a major cause of tyre bursting at high speeds.

Thanks @ehalin for your reply, but regret to disagree with your comment, as what is pressure in MKS system, its force/area,and unit is newton/sq meter,if we are talking about tyre, area (sq meter) of the tyre is constant but force is not, while we load the car increase force on same area of the tyre which increase pressure, here to mention you that weight unit is also newton whether its human body or some luggage, i dont know whether you got it or not let me make it easy for you, suppose you take out spare wheel of car and put one guage on it and then keep some weight on its tyre area let suppose 40 kg, if you will check pressure gauge it would show you more pressure because of weight, now suppose you continuously increasing load on tyre till it brusts, thats you also know that if we will put very heavy weight on tyre it will definately brust at one time as its common sense, but the question is why it would brust, and the answer is because of high pressure which exceeded from its maximum allowable pressure, because of load which we applied on it, so i am still stuck with my opinion that tyre pressure increase with load.
And yes i also checked in my car manual how to check tyre pressure, it is written there, always check tyre pressure in cold condition means car is not driven for atleast 4-5hours, in honda city pressure normally written on driver side door, in mycar its written 32 for front two tyres while 30 for rear side tyres

[gfkhan]

Thank you very much for clarifying the Physics involved in tyre pressure and also explaining the practical experiments. But have you ever checked the pressure with and without load in tyres? I think you have never done that. A truck tyre after loading even 10 tonnes of goods does not change its pressure. Tyre pressure changes only when more air is pushed or reduced or its temperature changes. This is coming from a famous physics formula which says that P x V / T (for a properly inflated tyre variation in V is negligible) of a compressible fluid remains always constant. Actually when you load a tyre its contact area with the ground increases and since pressure is always mentioned in pounds per square inch which being constant at the time of application; the increase in sq inches of contact area with the ground allows it to carry more load i.e., more total force exerted by the vehicle to the ground.
When load is put on the tyre. There is some flex in the tyre wall. More load and there is more flexing. This continuous flexing and relaxing of tyre side walls at high speeds (when the tyres are under inflated or vice versa the vehicle is overloaded) tend to overheat the tyre which is a major cause of tyre bursting at high speeds.

Thanks @ehalin for wonderful explaination, thats true i never checked car tyre press before and after load, i was taking area of tyre as constant and was unaware of increasing tyre contact area with the ground in loaded condition, which definately make some sense to keep pressure constant in any condition,so uptil now i do agree with your explaination, but for sure i will check my car's tyre press with and without load and i am sure by your good explaination that it will be same as you said.