It’s a common myth that a bit of extra air is harmless — or even good for fuel economy. In reality, overinflating your tyres trades away grip, comfort and even tread life for a marginal saving. The key mistake is confusing the sidewall maximum with the placard pressure: the sidewall number is the tyre’s ceiling, not a target. Here’s exactly what happens when you run your tyres too hard.
What does overinflation do to a tyre?
Too much air makes the tread bow outward in the middle, so the tyre rides on a narrower strip down its centre instead of its full width. That single change causes most of the problems below.
| Effect | Why it happens |
|---|---|
| Centre tread wear | The middle of the tread carries the load and scrubs away first |
| Harsh, skittish ride | An over-stiff tyre transmits every bump instead of absorbing it |
| Less grip & longer braking | A smaller contact patch means less rubber on the road |
| Worse wet performance | Reduced traction and a higher aquaplaning risk in the rain |
| Impact damage risk | A hard tyre has less give, so a pothole is more likely to bruise or bubble it |
Does overinflation wear tyres out faster?
Yes — unevenly. Because the load concentrates on the centre rib, that strip wears down long before the shoulders, and the whole tyre reaches the 1.5mm legal minimum in the middle while the edges still look healthy. That’s money wasted: you replace a tyre that has usable rubber left on its shoulders. A tyre showing a bald centre strip with good edges is the classic signature of chronic overinflation — see centre wear on tyres.
Does overinflation actually hurt grip and braking?
It does. Grip comes from the contact patch — the footprint of rubber touching the road. Overinflation rounds the tread and shrinks that footprint, so there’s less rubber doing the work. The practical result is longer braking distances and less bite when you corner, and it’s worse in the wet, where a smaller, harder patch clears less water and is quicker to aquaplane. On Australian summer roads that swing from bone-dry to sudden downpour, that’s a safety trade you don’t want to make.
Is overinflation more dangerous for pothole and kerb hits?
A correctly inflated tyre flexes to absorb a sharp impact; an overinflated one is rigid and takes the hit through the casing instead. That raises the risk of an internal bruise, a sidewall bubble, or immediate pothole damage to the tyre and wheel. After Australia’s wet-season potholes, that’s a real risk on many roads.
What about fuel economy — isn’t more pressure better?
A slightly harder tyre does roll with marginally less resistance, which is why the myth persists. But the fuel saving from running above the placard is tiny, and it’s swamped by the costs: faster centre wear, a rougher ride, less grip and more impact damage. The safe way to protect fuel economy is simply to keep tyres at placard, not above it — more in tyre pressure and fuel economy.
How much is too much?
Follow the placard — the sticker on the driver’s door jamb, fuel flap or glovebox — and set pressures cold. Remember that heat and driving raise pressure naturally (around 1 psi per 5–6°C), so a high reading on a hot tyre after a highway run is normal and shouldn’t be bled down. The number to never chase is the sidewall “max press” figure, which is the tyre’s structural ceiling at its maximum load, not a recommendation. One deliberate exception: airing up slightly for a heavy load or towing, as set out on the placard’s laden column or our loaded road-trip guide.
Frequently asked questions
Can overinflated tyres burst? Rarely from air pressure alone at normal road numbers, but an overinflated tyre is more likely to be damaged by a pothole or kerb strike, which can then fail.
How do I know my tyres are overinflated? Tell-tale signs are a bald strip down the centre of the tread, a bouncy or skittish ride, and a gauge reading above your placard when cold.
Should I ever inflate to the sidewall maximum? No. That figure is the tyre’s ceiling at maximum load, not a target. Use the placard.
Is 5 psi over the placard a problem? A few psi high won’t wreck a tyre, but it noticeably firms the ride and starts favouring centre wear. Correct it at your next check.
Bottom line
Overinflation is not a shortcut to better economy — it costs you grip, comfort and even tread life, and makes impact damage more likely. Set your tyres to the placard, cold, and leave the sidewall maximum well alone.
Sources: RACV — tyre pressure guide. Figures are a guide; confirm your vehicle’s pressures on the placard.
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