It’s well said that your Car Tyres are your only ‘effective’ means of communication with the road you’re travelling on – which can make or mar your life!

So what’s this Tyre Pressures noise all about??

Some Basic Facts

1) Rest assured that the OE Specs of Tyres that come with your Car are the best suited for the pupose it’s intended to be used for – otherwise the Car won’t be cleared for ‘Street Use’ or ‘Registration’ - if you please.

2) There’s an uncalled for mania in our Country to phooh-phooh such OE Tyre specs, especially on the 80Bhp+ Cars – courtesy the ill-informed Automedia.

3) When I say ill-informed, cross check it with the multitude of Street Cars in the developed Countries – where none dare think of changing the OE Specs coz their Insurance Policies will promptly go invalid ! And a crash out there, whether coz of Tyres or not, can set you back by some millions in hard cash!!

So what about it – where do we go from here?

Some funda-bashing is called for now - as follows:
1) Every 'chosen' Tyre has a ‘safe’ load bearing capacity - say 1/4th the 'weight' of a Car.
2) The Weight of a Car varies - from 'Kerb' to 'fully loaded' - for understandable reasons. This difference in loading can be as much as 500 kgs for the larger
Cars!
3) The 'ideal foot-print' of a Tyre is a function of the inflation pressure when 'cold' AS WELL AS the load on it.
4) While in motion - even a 'correctly' inflated tyre will 'warm-up' - a) coz of internal heat generation due it's own/inevitable 'flexing' AND b) friction on the road surface. Consequently, the 'cold' pressures can go up by as much as 15% when on a high speed cruise after some time. But this is all taken care of while stipulating the cold tyre pressures.
5) Car makers take a medium route - by specifying cold pressures for - a) Part load which is usually the case and b) to strike a good balance between Fuel consumption - higher the cold pressures the better and b) ride quality - lower the cold pressure the better.
6) Therefore, when going on a long trip 'when fully loaded' - as is usually the case with most of us ‘Injuns’ - inflation by say 10%+ not only guards against excessive tyre flexing/thus heat build-up but due to sustained high speed cruises in such situations, also guards against their overheating and possible premature failure due to road surface friction.
7) The ‘effects’ of various degrees of ‘inflation’ are illustrated in the sketch below:

8) It’s, therefore, obvious that one has to aim at the ‘Proper Inflation’ one as above – to give the best possible ‘communication’ between the Car and the Road - particularly when on a long cruise – more from safety considerations than any thing else.
9) While at it, it may be noted that an ‘under-inflated’ Tyre will wear out faster from its outer edges and an ‘over-inflated one from the middle. Only the ‘properly-inflated’ one can ensure even tread wear across the width of it.