If you want to increase your chance of crashing, don't check your tyre pressures every fortnight. It's that simple. Otherwise, make sure you’re driving with the right amount of air in your tyres. Maybe it's not the sexiest thing you'll ever do, but those pressures are critical to maximising your car’s grip on the road, and its stability in corners and while braking.
Worryingly, 25 per cent of cars drive around with at least one tyre seriously under-inflated. This adds to the problems you’ll face if you need to swerve or brake. One low tyre and three good ones adds a load of dynamic instability to swerving or emergency stopping.
It is impossible to see if your tyre pressures are low just by looking at them (unless they’re r-e-a-l-l-y low). You need to use a tyre pressure gauge. Those at the service station are fine, broadly (compared with, say, not using one at all) but it’s probably better, for consistency, to spend $30 or so on a decent gauge of your own for the glovebox.
The air at the service station is free, preversely (like, the fuel will be $60 or something, but the air is free) and the only reason people buy the fuel and overlook the air is that one of those commodities is essential to keeping the car going while the other is not. In practise it’s neither too hard nor too time consuming to check your tyre pressures once a fortnight like the owner’s manual says. It could save your neck – and it will certainly save you money because partly under-inflated tyres wear out very fast compared with those operating at the correct pressures. And nobody likes contributing disproportionately to the profits of Goodyear, Bridgestone, Pirelli, or others…
Every car has a tyre placard, usually inside the driver’s door frame, that specifies the manufacturer’s recommended operating pressure. Every tyre has a maximum cold inflation pressure embossed on the sidewall. The correct operating pressure for your car is somewhere between the two – just check how the tyres are wearing to see how yours are going. If the pressures are too low for your car and your style of driving, the tyres will be wearing out on the outside edges more than in the middle of the tread face. If the pressures are too high, they’ll be wearing out first in the middle of the tread face.
The reason there's not a 'one size fits all' answer to tyre pressures for everyone is that cars are all different weights, tyres are all different sizes and proportions, and people all drive differently - the more aggressively you attack corners, or the more heavily loaded you drive, the more pressure you'll need to keep the tyre sufficiently rigid.
'Cold inflation pressure' means before the tyres warm up (ie not after half an hour’s driving), so the place to check your tyre pressures is at a service station close to home or work. All of the pressure recommendations relating to tyres (on the placard and the sidewall) are cold inflation pressures.