Tyre tool checks on spare's air.
But now there is a clever new gadget which tells you at a glance - without moving everything in the boot - whether the tyre is at the correct pressure.
Air In Your Spare kit from Pirtek incorporates a tyre pressure gauge which visually flags up any drop in pressure.
When the tyre is correctly inflated the cap gauge is green. This turns yellow when pressure has dropped by 4psi and becomes red when 8psi has been lost and the tyre is dangerously low.
And because the gauge is at the end of a long pipe fitted to your tyre it is always in view when you open the boot - even if your spare wheel isn't.
Air In Your Spare is approved by the Tyre Industry Council, costs pounds 15 and takes minutes to fit.
Frighteningly, over 80 per cent of spare tyres are either flat or badly deflated.
Pirtek sales director Russell Mundell said: "More than two million UK motorists are putting their lives at risk by never checking tyre pressure and six per cent of all fatal motorway accidents are caused by the sudden failure of under-inflated tyres."
To buy one call 0800 02 34124 or visit the website www.pirtek.co.uk
WARNING... the tyre kit.