It’s one of the most common fears when Australians upsize their 4WD or ute tyres: “Will this void my warranty?” The short version is reassuring, but the detail matters — because a modification can cost you a claim in the wrong circumstances. This is general information, not legal advice; check your own situation with the dealer, manufacturer and, if needed, a consumer-law service.

Does fitting bigger tyres automatically void the warranty?

No. As the Australian Automotive Aftermarket Association puts it plainly, “modifying a vehicle does not automatically void a manufacturer’s warranty.” Your new-car warranty still covers manufacturing defects on its own terms. What a modification does is raise the risk that a related claim gets refused — not cancel the whole warranty.

What does Australian Consumer Law actually say?

Separate from any voluntary manufacturer warranty, every new car sold in Australia carries consumer guarantees under the Australian Consumer Law (ACL) — including that the vehicle is of acceptable quality. A manufacturer warranty cannot exclude or reduce those guarantees. Crucially, the ACL guarantees apply to the vehicle, its parts and accessories whether or not a manufacturer warranty is offered, and a parts supplier must provide a remedy if its product fails to meet them.

In practice this means a maker must still fix a genuine manufacturing fault even on a modified vehicle — unless the modification caused the fault. A cracked touchscreen or a failed water pump has nothing to do with your tyres, so those claims stand. A worn clutch or driveline failure on a heavily upsized, re-geared truck is a different conversation.

When can a dealer legitimately refuse a claim?

A claim can be fairly declined when the fault is traced to the change you made. Bigger, heavier tyres raise the risk in a few specific areas:

Note that normal wear and tear generally isn’t covered by warranty anyway, so early clutch wear from taller gearing is usually the owner’s cost regardless.

How to protect yourself when you upsize

A few habits keep you on the right side of a dispute:

• Use reputable suppliers and fitters, and keep all invoices and fitment records.
• Stay within legal and engineering limits — if a GVM upgrade or an engineer’s certificate is required in your state, get it.
• Recalibrate the speedo where needed and keep the correct load rating.
• Ask the supplier directly about the warranty on the parts and fitting — their products carry ACL guarantees too.

It’s also worth remembering a separate but related issue: modifications can affect your car insurance, so tell your insurer about bigger wheels and tyres. And if you’re relying on the tyre maker’s own cover, see what tyre brand warranties actually cover.

What about aftermarket parts failing?

If an aftermarket tyre or wheel itself fails, that’s the supplier’s responsibility under ACL guarantees, not the car maker’s. This split is useful: your vehicle maker covers the vehicle; the parts supplier covers their parts. Choosing established brands and fitters means there’s someone accountable if something goes wrong.

Frequently asked questions

Can a dealer refuse all servicing because I fitted bigger tyres? No. They can’t cancel your warranty or consumer guarantees outright; they can only decline a claim where the modification caused the specific fault.

Who has to prove the tyres caused the fault? The question of causation is fact-specific. If you disagree with a refusal, a consumer-law service or the AAAA’s legal assist line can help; this article is general information only.

Do mild upsizes carry the same risk? Staying close to standard size (as with a two-inch lift) and correct load rating keeps the risk low.

Does it affect fuel claims? No — but bigger tyres do cost more fuel; see the 33-inch fuel-economy guide.

Bottom line: Bigger tyres don’t void your new car warranty in Australia. A maker can’t blanket-cancel cover, and ACL consumer guarantees sit above any warranty. A claim can only be fairly refused for a fault the modification actually caused — so fit within the rules, keep your records, and use reputable suppliers.

This is general information, not legal advice. Laws and manufacturer policies change; confirm your situation with the dealer, manufacturer, your insurer and a consumer-law service where needed.

Further reading on how modifications and warranties interact: Auto Expert on tyre size and warranty.