Spare Tyre Pressure: The Number Everyone Forgets
TL;DR: Check your spare at the same time as your other tyres. A full-size spare runs the placard pressure for the axle it will go on. A space-saver needs a much higher pressure — usually around 420 kPa (60 psi), printed on the wheel. Spares leak slowly, so a forgotten one is often half-flat the day you finally need it.
Most Australian drivers never touch their spare until they are stranded on the shoulder of a highway. By then it is too late to discover it has quietly lost half its air. The spare is a tyre like any other: it leaks, it ages, and it has a correct pressure that is often nothing like the pressure in the four tyres you drive on every day. Getting that number right is the difference between a 20-minute wheel change and a very bad afternoon.
What pressure should a full-size spare be?
A full-size spare should be set to the pressure on your vehicle’s tyre placard for the axle it is most likely to go onto — in practice, the higher of the front or rear figures is a safe default, because you can always let a little air out once it is fitted. If your placard lists a specific “spare” pressure, use that. The placard lives in the driver’s door jamb, inside the fuel flap, or in the glovebox.
Because a full-size spare matches your road tyres in size and construction, it follows exactly the same rule as the rest of your set: follow the placard pressure, not the sidewall maximum. The big number moulded into the sidewall is the tyre’s maximum cold pressure, not its recommended one.
What pressure should a space-saver spare be?
A space-saver (the skinny temporary wheel) is the one that trips people up. It is designed to run at a much higher pressure than a normal tyre — typically around 420 kPa (60 psi) — because it is narrow and has to carry the car’s weight on a small contact patch. The exact figure is printed on a label on the wheel itself or moulded into the tyre. Always read that label; do not assume it takes the same pressure as your road tyres.
Underinflate a space-saver and it will squirm, overheat and wear out in a few hundred kilometres. It is already a compromise: most are limited to 80 km/h and only a short distance, and they belong on a non-driven axle where possible. Our full guide to how far and how fast you can really drive on a space-saver covers those limits in detail.
How often should you check your spare?
Check the spare every time you check your other tyres — at minimum once a month and before any long trip. Spares lose air slowly through the valve and the rubber itself, and a spare that has sat untouched for a year can easily be 30–40 kPa down or worse. Because it is hidden under the boot floor or slung under the vehicle, there is no visual warning and often no sensor watching it.
This is the catch with tyre pressure monitoring systems: most factory TPMS set-ups do not monitor the spare. Your dash can read “all good” while the spare sits flat in the well. Fold checking the spare into the same habit as checking the others — the whole process is covered in how often you should check tyre pressures.
Where do you find the correct spare pressure?
Two places, depending on the spare:
- Full-size spare: the vehicle’s tyre placard (door jamb / fuel flap / glovebox). Use the axle figure, or the listed spare figure if there is one.
- Space-saver: the label stuck to the temporary wheel, or the moulding on the tyre — usually about 420 kPa (60 psi).
| Spare type | Typical cold pressure | Where to find the number | Notes |
|---|---|---|---|
| Full-size spare | Same as placard (often ~230–260 kPa for cars; higher for utes/4WDs) | Tyre placard | Can be rotated into normal use |
| Space-saver | ~420 kPa (60 psi) | Label on the wheel / tyre moulding | 80 km/h, short distance, non-driven axle |
| 4WD/ute full-size | Per placard — often 300 kPa+ when loaded | Tyre placard | Confirm loaded vs unloaded figures |
Figures above are a guide for 2026 — always use the number on your own placard or wheel label, and confirm with a tyre fitter if you are unsure.
Does keeping the spare at high pressure hurt it?
No. A space-saver is engineered to sit at ~420 kPa and to be driven at that pressure; leaving it there is correct, not harmful. A full-size spare sitting a touch high is also fine — you simply bleed it down to the placard figure when you fit it. The real enemy of a spare is being forgotten: slowly going flat, and quietly ageing past the point where it is safe to use even though the tread looks brand new.
Roadside assistance is not a substitute for a properly inflated spare, either. As we explain in what roadside tyre cover actually includes, the service will typically fit your roadworthy spare or tow you — it will not magically produce a new tyre on the shoulder.
What if the spare is flat when you need it?
If you find the spare soft at the roadside, a 12 V inflator will usually get a full-size spare up to pressure in a few minutes, and most will reach 420 kPa for a space-saver (check the compressor’s rating). Inflate it before fitting if you can, drive gently, and get it checked properly as soon as possible. If you have never changed a wheel, read how to change a tyre safely on an Australian highway first — doing it on a live traffic lane is genuinely dangerous.
For plain-English background on temporary spares and their pressures, the NRMA’s guide to space-saver tyres and Tyrepower’s space-saver advice are good starting points, and most tyre manufacturers publish the same guidance.
Bottom line: The spare has its own correct pressure — placard figure for a full-size, around 420 kPa for a space-saver — and it leaks just like any other tyre. Check it monthly and before long trips, because the one time you need it is the worst possible time to find it flat.
Frequently asked questions
What PSI should my space-saver spare be?
Most space-savers in Australia are set to around 60 psi (420 kPa). The exact figure is printed on a label on the wheel — always read it rather than assuming, as some differ.
Is the spare tyre the same pressure as my normal tyres?
Only if it is a full-size spare, in which case it follows the placard. A space-saver runs much higher — usually about double a typical car tyre’s pressure.
Does my car’s TPMS check the spare?
Almost never. Most factory tyre pressure monitoring systems watch the four road wheels only, so you must check the spare manually.
How often should I check spare tyre pressure?
Monthly, and always before a long or remote trip. Spares lose air slowly and give no warning when they do.
Can I drive on a space-saver that is a bit underinflated?
Avoid it. An underinflated space-saver overheats, handles poorly and can fail. Inflate it to the label figure first, keep under 80 km/h, and replace or repair your main tyre as soon as possible.
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