IT’S THE LAW

4 x 4 Australia - - Gear -

A TYRE plac­ard with avail­able tyre sizes and min­i­mum speed and load rat­ings has to be fit­ted to all ve­hi­cles to meet Aus­tralian De­sign Rules. Th­ese are the cor­rect tyres for your ve­hi­cle, al­though there are a few ex­cep­tions (as we will ex­plain). On most four-wheel drives, you’ll find the tyre plac­ard on a door jamb or glove­box lid.

Al­ways make sure load rat­ings meet or ex­ceed the min­i­mum for your ve­hi­cle, be­cause you could be faced with a fine or, even worse, a tyre blow-out. And, if the tyres con­trib­uted to the crash, your in­sur­ance mightn’t cover you.

Wider rims and tyres are of­ten a good thing, but to stay le­gal the tyres can’t be wider than the guards. Too-wide tyres can rub against brake lines, the sus­pen­sion or guard lips, and none of this will end well. The wider tyres spray mud and wa­ter ev­ery­where, too. Fit flares and – if needed – trim the guards.

You might have no choice but to fit big­ger tyres be­cause of a lim­ited range of sizes, or be­cause you want to in­crease ground clear­ance with a taller tyre. You don’t have to stick with the tyre sizes on the plac­ard, but you do need to keep the over­all rolling ra­dius to a max­i­mum 50mm over stan­dard to stay le­gal. The 50mm is for to­tal ride height change, so keep that in mind if you have (or are get­ting) a lift kit.

Most tyre man­u­fac­tur­ers list the over­all rolling ra­dius of their tyres, so it’s pretty easy to work out what per­cent­age a cer­tain size is over your four-wheel drive’s stan­dard boots.

You’ve got wrig­gle room with speed rat­ing, too. The law al­lows lower-speedrated tyres for ‘off-road’ ve­hi­cles. That min­i­mum is N (140km/h). Don’t be tempted to drive over those rated speeds on un­re­stricted NT high­ways, be­cause you’re head­ing for a tyre blowout and a nasty crash. The tyres aren’t built to go that fast for very long.

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