The correct caravan or trailer tyre pressure is the cold inflation pressure on the trailer’s tyre placard, read together with the tyre size and load rating printed beside it. There is no single psi figure that suits every van or trailer. To convert, multiply psi by 6.895 to get kPa, or multiply kPa by 0.145 to get psi.
This guide is for tyre shops and workshops. It covers where the numbers come from, how to check them, what to tell customers at the counter, and what to confirm before you quote C or LT tyres for a van or trailer.
Where the pressure figure comes from
Australian Design Rule 42/05 requires category TA and TB trailers to carry a tyre placard. The placard must include at least the manufacturer’s recommended:
- tyre size
- tyre load rating
- speed rating
- cold inflation pressure
TA (very light) and TB (light) are defined by Gross Trailer Mass. A TA trailer is single-axled with a GTM of no more than 0.75 tonne. A TB trailer has a GTM of no more than 3.5 tonnes. Above 3.5 tonnes GTM the trailer is a TC or TD, and ADR 42 does not list those categories in its placard clause, so take the pressure from the trailer or tyre manufacturer.
The trailer’s vehicle plate is a separate item. Under ADR 61/03 it must show the manufacturer or make, the VIN, the Aggregate Trailer Mass (ATM) and the Gross Trailer Mass (GTM). Trailers up to 4.5 tonnes ATM must also show the tare mass. Read both the placard and the plate before you set a pressure or quote a tyre. You can read the rules on the Federal Register of Legislation: ADR 42/05, ADR 61/03 and the ADR definitions and vehicle categories.
ATM or GTM: which mass the tyres carry
The two figures on the plate measure different things:
- ATM is the total mass of the laden trailer at the manufacturer’s maximum recommended load. It includes the mass the coupling puts onto the tow vehicle.
- GTM is the mass the trailer’s axles put on the ground when it is coupled and carrying its maximum load.
The tyres carry the GTM, not the ATM, because the ball weight sits on the tow vehicle. Dividing GTM by the number of tyres on the trailer’s axles gives the average load each tyre carries when the trailer is fully loaded. For example, a single-axle trailer with a GTM of 1,600 kg on two tyres averages 800 kg per tyre. Real loads are rarely spread perfectly evenly, so treat this as a quick check. It does not replace the placard’s load rating.
How to check caravan and trailer tyre pressure
- Check cold. The placard gives a cold inflation pressure, so compare it with a reading taken before the tyres have warmed up from driving.
- Use a gauge you trust. Read every trailer tyre, including the spare.
- Compare with the placard, then with the tyre. The fitted tyre should be the placard size, with load and speed ratings no lower than the placard’s. If it differs, check the fitted tyre’s size, load index and speed rating against the placard and the caravan or trailer manufacturer’s data before you set a pressure.
- Refit the valve caps. VicRoads’ tyre maintenance sheet for light vehicles says the valve cap must be firmly screwed on after checking and adjusting pressures.
- Look at the tyre while you’re there. The same sheet says to check for deep cuts, cracks, bulges or other damage likely to cause failure, and to remove a damaged tyre. It also sets a minimum tread depth of 1.5 mm in all principal grooves.
The tow vehicle has its own placard and handbook. Some list a different pressure for a loaded vehicle. Our passenger vs LT tyres guide covers the tow-vehicle side in more detail.
kPa to psi conversion tables
Customers often have a placard figure in one unit and a gauge that reads in the other. One psi is 6.894757 kPa (NIST conversion factor). The tables round to the nearest whole kPa or to one decimal place in psi. They are conversion aids only, not recommended pressures.
| psi | kPa |
|---|---|
| 20 | 138 |
| 25 | 172 |
| 30 | 207 |
| 35 | 241 |
| 40 | 276 |
| 45 | 310 |
| 50 | 345 |
| 55 | 379 |
| 60 | 414 |
| 65 | 448 |
| 70 | 483 |
| 75 | 517 |
| 80 | 552 |
| kPa | psi |
|---|---|
| 150 | 21.8 |
| 200 | 29.0 |
| 250 | 36.3 |
| 300 | 43.5 |
| 350 | 50.8 |
| 400 | 58.0 |
| 450 | 65.3 |
| 500 | 72.5 |
| 550 | 79.8 |
| 600 | 87.0 |
Source: NIST Guide to the SI, Appendix B.8.
C and LT tyres on vans and trailers
If the placard calls for a commercial (C) or light-truck (LT) size, two things matter when you quote it:
- Keep the full marking. Tyres with similar width, aspect ratio and rim size can still differ in load capacity, construction and inflation requirements. Keep the C or LT in sizes such as 185R14C or LT215/75R15 on the order line.
- Read both load indices. C and LT sizes often show two numbers, such as 102/100. The first is the per-tyre rating in single fitment and the second is the per-tyre rating in dual fitment. On a standard trailer axle with one tyre per side, compare the single figure against the load you need. Our load index and speed rating guide lists 102 as 850 kg and 100 as 800 kg per tyre.
Construction can also change the pressure. As our passenger vs LT guide explains, an LT or commercial fitment may need a different operating pressure for the actual load. If a customer changes construction, size or load index from the placard, don’t assume the old pressure still applies. Get the figure for the new tyre from the trailer manufacturer or from the tyre’s load and inflation data.
Grenlander sizes with C or LT markings
These Grenlander patterns list C- or LT-marked sizes in their specification tables. The tables are manufacturer catalogue rows. Each row still has to be matched to the placard and confirmed for the application and for supply.
| Pattern | Category on our site | C/LT rows listed | Example row |
|---|---|---|---|
| L-MAX9 | Commercial | 34 C rows, R14 to R17 | 185R14C 102/100R 8PR |
| GREENTOUR A/S | Commercial | 19 C rows, R14 to R17 | 205/75R16C 113/111R 10PR |
| L-POWER28 | Commercial | 15 of 17 rows (C or LT), R12 to R14 | 175R13LT 97/95R 8PR |
| MULTIWAYS 52 | Commercial | 2 LT rows, R16 | 7.50R16LT 122/118N 14PR |
| STEADTREK AT | SUV & 4×4 (A/T) | 60 of 66 rows (C or LT) | LT235/75R15 104/101R 6PR |
| MAGA A/T TWO | SUV & 4×4 (A/T) | 21 of 47 rows (C or LT) | LT215/75R15 100/97Q 6PR |
For more 4×4-style LT sizes, see CONQUEWIND R/T, PREDATOR M/T and DRAK M/T. To search by size, enter the first part of the placard size on our tyre sizes page, or browse the commercial range by rim diameter.
What to tell customers at the counter
- Set pressures cold, from the trailer’s placard, and check the spare too.
- The van and the tow vehicle each have their own placard. Check both.
- If the van now carries more, or has had a mass upgrade, the original figures may no longer apply. Ask the trailer manufacturer.
- A tyre that keeps losing pressure, or shows cuts, bulges or uneven wear, needs a tyre professional to inspect it, not just more air.
Before you quote: a short checklist
- Photograph the trailer’s tyre placard and vehicle plate (ATM, GTM, tare).
- Record the size exactly as it appears on the placard, including any C or LT marking.
- Note the load rating and speed rating the placard calls for. Use the single-fitment index for a standard trailer axle.
- Pick a row with a load index and speed rating equal to or higher than the placard’s, then have any change of size or construction confirmed.
- Send the pattern, full size and ratings, quantity and delivery postcode in one enquiry.
Ready to order? Send a wholesale tyre enquiry. The enquiry preparation guide and the commercial van tyre ordering guide show how to set out each line.
Frequently asked questions
What should caravan tyre pressure be?
Use the cold inflation pressure on the caravan’s tyre placard, which ADR 42/05 requires on TA and TB trailers alongside the recommended size, load rating and speed rating. If the van runs a different tyre from the one on the placard, get the pressure from the caravan or tyre manufacturer.
What is the right tyre pressure for a trailer?
The same rule applies to any TA or TB trailer: start from its tyre placard and check the tyres cold. For trailers over 3.5 tonnes GTM, take the figure from the trailer or tyre manufacturer.
How do I convert kPa to psi?
Multiply kPa by 0.145. To go from psi to kPa, multiply by 6.895. For example, 300 kPa is about 43.5 psi and 40 psi is about 276 kPa.
Do LT or C tyres need a different pressure from passenger tyres?
They can. Construction and load rating affect the pressure needed for a given load, so don’t carry over a passenger-tyre figure. Use the placard, or the trailer or tyre manufacturer’s figure for the exact tyre fitted.
Grenlander specifications from the linked product pages, checked 20 October 2026. Regulatory references from the Federal Register of Legislation and the VicRoads Vehicle Standards Information 16 sheet (October 2021).