Why Car tire pressure is around 30 psi & road bike tire as 120 psi ?
One burnout will not ruin your tire, but it will probably shorten the tire life by a couple hundred miles down the road. You ride to have fun don't you?
I'm guessing somewhat, but I suspect a car tire would burst or leak at 120psi - the area is larger, so the force would be greater. Also, it would make for a very hard ride - tires are part of the suspension system. Higher pressures make for less rolling resistance, so racing bikes will compromise comfort for speed.
And a 15,000-25,000 lb farm tractor may have rear tire pressures of 12-15 lbs. The reason is that the larger the tire is, the more surface area that is in contact with the ground (the footprint as it's called). When you compare the vehicle weight to the surface area on the ground, the fewer pounds each square inch has to support. For example, a loaded motorcycle tire may be supporting 50 lbs/sq in (psi) of contact patch, an automobile 25-30 psi and a 15,000 farm tractor 15 psi. To go one step further, you can have a 60,000 lb bulldozer with LGP (wide, low ground pressure tracks) that has 3 psi. In fact, such a dozer can easily travel across ground so muddy that as soon as you step off, you sink in the mud up to your ankles. That said, the more pounds per square inch (of weight) that a tire has to support, the more air pressure required (also measured in pounds per square inch). Makes sense now, doesn't it?
No, not by a beginner, the longer the burn out the shorter the tire life. Good burners can blow out a brand new tire.
Everything that bikinkawboy has said is accurate but it doesn't address the actual issue for the pushbike. I can fit tyres to the bike of various widths which take pressures from 35 to 100 PSI. On a road bike I can get still narrower tyres up to 200 PSI. The advantage of the small high pressure tyres is that they are very light, have low rolling resistance and low wind resistance. With these tyres I can ride at speeds of around 35 Km/hr. The advantage of the fatter low pressure tyres is that they last a lot longer, have far better impact resistance and transmit less vibration to the rider. Usually they have enough rubber to permit a better tread for mud/snow/water handling capabilities. For the same amount of effort as the road bike the speed reduces to perhaps 20Km/hr for the 35 psi tyres. For intermediate or compromise tyres (1.5 inch 100 psi) I can ride at around 30Km/hr A car has plenty of power available so efficiency has been a low priority. Ride comfort, noise, cost per Km and safety are higher priorities so fat tyres with low pressures have taken over. In theory I could fit narrow high pressure tyres to a tractor too but it would cut into the ground and be unsuitable for use on dirt. So we select bigger fatter heavier tyres instead. We know that they are limited in speed capabilities and have high friction but this isn't an issue when plowing or slashing paddocks. The other issue is that it is very hard to make a big tyre take high pressures. The smaller the tyre the easier it is to make it strong enough to withstand the pressures. Even if we decided that a 200 psi tyre would be good for a car, it would be almost impossible to find materials that would withstand the forces. So big tyres normally can only withstand low pressures but with small tyres we have our choice.
