Quote:
Originally Posted by Rshrey22 My general rule of thumb for hatchbacks and sedans is to keep the pressure at 32 psi in city when speeds are below 80 km/h and for intercity commute aka highway travelling, I keep the pressure at 35 psi in all 4 tyres. |
As a maintenance engineer, I vary with this view and would like to brief this in a simple way. Hope it helps
Proper air pressure in a tyre helps to distribute the weight of a vehicle evenly across the tyre's tread pattern, so the vehicle is at it's most stable.
Under-inflated tyres tend to show wear on the outside edges of the tread, while over-inflated tyres show wear, down the middle of the tread.
Under-inflated tyre will flex more in cornering and stopping. It becomes less responsive and some of the performance and safety benefits built into the tire will be lost. Simply, it increases the area of contact with road. Often, reduction of air pressure is used momentarily while 'off roading' in ghats to avoid 'rolling'. I have seen some VIPs prefer to keep lower pressure to have a smooth ride, albeit at the cost of tyres ,mileage and suspension.
On the other hand, over-inflated tyres lose traction as shape of the tyre gets deformed by excessive air pressure, decreasing the tyres footprint on the road. Simply, it reduces the area of contact with road surface. It becomes stiffer and may not react as expected to road hazards like potholes. Over-inflation can even give a harsh, noisy ride.
Often, it is believed that with increase of load, tyre pressure has to be increased above the norms prescribed by the manufacturer. Actually its not so since air volume requirement doesn't increase in exact proportion with load, above the norms. Hence, standard ratings given by the manufacturer takes care of it, by itself.
So, maintaining the correct air pressure recommended for that tyre for that vehicle is the proven and safe bet. I had the Swift Vxi first generation and 33 psi was the recommended pressure for all the 4 wheels. I changed them after 5 years and 40K km, as a precaution but still tyres were decent enough.
Finally, air pressure be checked , atleast once in a month, if not regularly, while the tyres are cold, say, first thing in the morning. Heat generated by driving, an increase in air temperature as the day goes on, and even the heat of the sun shining on the tyres can temporarily increase tyre pressure, so most accurate reading is got, when tyres are cold. And, finally the well calibrated gauge is all the most important one.