4WD Tyre Pressure Calculator
Enter the highway pressure you run when loaded and get a starting pressure for gravel, rocks, mud and sand. Below that: a check for the 4 PSI rule and a PSI, kPa and bar converter.
How the tyre pressure calculator works
The figures come from our guide How to Determine PSI for Your 4WD Tyres. It gives a range for each surface. A heavier 4WD that needs a higher highway pressure also needs to stay at the upper end of each range off road, so the calculator places you in the range by your highway pressure: 32 PSI gives the bottom of the range, 40 PSI the top.
| Terrain | Starting PSI | Max speed |
|---|---|---|
| Highway | 32 to 40 PSI | 100 km/h |
| Gravel & corrugations | 25 to 30 PSI | 60 km/h |
| Rocky tracks | 20 to 25 PSI | 25 km/h |
| Mud | 20 to 25 PSI | 20 km/h |
| Soft sand | 16 to 20 PSI | 20 km/h |
Before you let air out
- Check pressures when the tyres are cold, with a gauge you trust.
- The lower the pressure, the slower you drive. Low pressures at speed overheat the sidewalls and can roll a tyre off the rim.
- On sand, start around 18 PSI and only go lower if you are still struggling. Don’t go below 12 PSI.
- Carry a compressor and pump back up to your highway pressure before you return to the bitumen.
- The pressure on your tyre placard is the maker’s figure for the road. Don’t run below it on the highway.
Common questions
What PSI should 4WD tyres be on sand?
For soft sand most four wheel drives start between 16 and 20 PSI. Start around 18 PSI and only drop further, to 12 to 14 PSI, if you are still struggling. The lower you go, the slower you must drive.
What is the 4 PSI rule?
Set your cold pressure, drive for about an hour on the highway and measure again. The hot pressure should be about 4 PSI higher. A rise of 6 PSI or more means the cold pressure was too low. A rise of only 2 PSI means it was too high.
How do I convert PSI to kPa?
Multiply PSI by 6.895 to get kPa, so 35 PSI is about 241 kPa. To go from kPa to PSI, divide by 6.895. One bar is 100 kPa, or about 14.5 PSI.
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