A trailer tyre load rating is not a figure you estimate from the tyre size or the trailer’s brochure. It is a specific number—the load-capacity index—moulded into the sidewall, and on trailers up to 3.5 tonnes it is restated on a tyre placard the manufacturer is required to fit.
Two Australian Design Rules do most of the work. ADR 95/00 – Installation of Tyres decides what may be fitted to a trailer. ADR 42/05 – General Safety Requirements decides what the placard must say. The tyre itself is then governed by ADR 23/03 or ADR 96/00 depending on which class of tyre it is.
This explainer sets out what those documents require, what the markings mean, and—just as importantly—what the rules do not say.
Which rule applies to a trailer
ADR 95/00 applies to all vehicle categories, including the four trailer categories: TA (UN category O1), TB (O2), TC (O3) and TD (O4). The applicability table gives 1 July 2019 for all new model vehicles. For all other vehicles there is no mandatory application date; they may comply with ADR 95/00 or continue to comply with the older Australian Design Rule 42/04 – General Safety Requirements.
ADR 42/05 reinforces the link. Its Table 4 lists the other rules a T-group vehicle certified to that standard must also be certified to, and ADR 95 is marked as applicable to TA, TB, TC and TD alike.
Most Australian camper trailers sit in TA or TB—very light and light trailers—which matters because the placard requirement below does not extend to every category.
| Category | UN code | Common description |
|---|---|---|
| TA | O1 | Very light trailer |
| TB | O2 | Light trailer |
| TC | O3 | Medium trailer |
| TD | O4 | Heavy trailer |
For where those categories come from and how they relate to mass limits, read the ATM, GTM and tare explainer.
What ADR 95/00 requires of trailer tyres
The requirements for T-group vehicles are short and worth reading closely. Clause 5.3.1 states that all tyres normally fitted to the vehicle—excluding any temporary-use spare—must be suitable for the vehicle model or type, “particularly with respect to their dimensions, speed and load performance characteristics”.
The remaining clauses route the tyre to its own standard:
- a trailer fitted with passenger car tyres: each new tyre must comply with ADR 23 – Passenger Car Tyres (clause 5.3.2);
- a trailer fitted with light truck or truck/bus tyres: each new tyre must comply with ADR 96 – Commercial Vehicle Tyres (clause 5.3.3);
- a trailer fitted with retreaded tyres: each retreaded tyre must comply with the technical requirements of AS 1973–1993 (clause 5.3.4);
- manufacturers must not fit tyres requiring a cold inflation pressure above 825 kPa for radial-ply tyres, or 700 kPa for other tyres, to achieve the manufacturer’s rated GTM (clause 5.3.5).
That last clause is a useful detail. For passenger and goods vehicles the equivalent clause is written against GVM. For trailers it is written against GTM—the mass carried through the trailer’s own tyres—which is the figure a trailer’s tyres actually have to support.
The load-capacity index is the number that counts
ADR 23/03 defines the load-capacity index as “a number associated to the reference mass a tyre can carry when operated in conformity with requirements governing utilization specified by the manufacturer”.
ADR 96/00 uses a slightly wider definition for commercial tyres: one or two numbers indicating the load the tyre can carry in single, or in single and dual, operation at the speed corresponding to its speed category. A commercial tyre can therefore carry two sets of indices.
ADR 23/03 also ties the index to a maximum load rating: for speeds not exceeding 210 km/h, the maximum load rating must not exceed the value associated with the tyre’s load-capacity index.
The index-to-mass conversion is published in the rules themselves. Both ADR 96/00 Annex 4 and ADR 23/03 Annex 4 list the values, and they agree across the range they share.
| Load-capacity index | Mass per tyre (kg) |
|---|---|
| 75 | 387 |
| 80 | 450 |
| 85 | 515 |
| 90 | 600 |
| 95 | 690 |
| 100 | 800 |
| 104 | 900 |
| 108 | 1 000 |
| 110 | 1 060 |
| 112 | 1 120 |
| 115 | 1 215 |
| 118 | 1 320 |
| 120 | 1 400 |
| 121 | 1 450 |
Indices below 75 and above 121 exist; ADR 23/03 Annex 4 runs from 0 to 120 and ADR 96/00 Annex 4 runs from 60 to 200. Read the value for the exact index on your tyre rather than interpolating between the rows above.
The speed symbol, and what it does not mean
The speed-category symbol is a letter, and the two standards publish different ranges because they cover different tyre classes.
| Symbol | Speed (km/h) | Listed in |
|---|---|---|
| F | 80 | ADR 96/00 |
| G | 90 | ADR 96/00 |
| J | 100 | ADR 96/00 |
| K | 110 | ADR 96/00 |
| L | 120 | both |
| M | 130 | both |
| N | 140 | both |
| P | 150 | both |
| Q | 160 | both |
| R | 170 | both |
| S | 180 | both |
| T | 190 | both |
| U | 200 | both |
| H | 210 | both |
| V | 240 | ADR 23/03 |
| W | 270 | ADR 23/03 |
| Y | 300 | ADR 23/03 |
ADR 96/00 attaches an explicit caution to its table. The symbols and speeds are shown to match those used for passenger cars, and the standard states they “should not be taken to indicate the speeds at which commercial vehicles fitted with such tyres may be operated on the roads”.
A speed symbol is a tyre capability declared under a test standard. It is not a road speed limit, and it is not permission to travel at that speed.
ADR 96/00 also refers to a table of load-capacity variation with speed, in its Annex 8, which sets out how the load a tyre can withstand changes when it is used at speeds different from the one matching its nominal speed symbol. The single index number is therefore a reference point, not an unconditional guarantee.
The trailer tyre placard on TA and TB trailers
ADR 42/05 clause 20.1 is specific. Category MA, MB, MC, MD, NA, NB1, TA and TB vehicles must be fitted with a tyre placard that includes at least the manufacturer’s recommended:
- tyre size;
- tyre load rating;
- speed rating; and
- cold inflation pressure.
Two points follow directly from the text. First, the placard is a manufacturer recommendation for that trailer, which is what makes it the reference for any later replacement. Second, TC and TD are not in that list—the placard clause does not extend to medium and heavy trailers, even though ADR 95 does.
ADR 42/05 also addresses rims. Clause 19.2.1, which applies to vehicles other than the L-group, requires all rims normally fitted to be suitable for the vehicle model or type, particularly with respect to their dimensions, speed and load performance characteristics. The numeric rim requirement in clause 19.1.1—that the sum of rim load capacities must not be less than GVM—applies to L-group vehicles only.
The placard is a different document from the trailer’s identification and compliance plate. For what that plate carries, see our guide to the trailer compliance plate under VSB1.
Which tyre standard covers your trailer
ADR 23/03 and ADR 96/00 divide the work by tyre class, and they do so by referencing the trailer categories directly.
ADR 23/03 covers new pneumatic tyres designed primarily for passenger cars and other light vehicles, “including light trailers”. Its requirements clause is written for Class C1 tyres, designed primarily for UN categories M1, N1, O1 and O2. It does not apply to light truck or truck/bus tyres—Class C2 or C3—which it identifies as designed primarily for UN categories M2, N2, N3, O3 and O4.
ADR 96/00 is the mirror image: it does not apply to Class C1 passenger car tyres for M1, N1, O1 and O2.
Both standards exclude retreaded tyres fitted to trailers and temporary-use spare units from their own scope. For a trailer, the retread requirement arrives instead through ADR 95/00 clause 5.3.4 and AS 1973–1993.
In practice, a camper trailer on passenger-car tyres is in ADR 23/03 territory, and the same trailer on light-truck tyres is in ADR 96/00 territory. The markings differ accordingly.
Markings you can check yourself
ADR 23/03 requires, as a minimum, the markings at paragraphs 3.1.1 to 3.1.11 of its appendix plus the date of manufacture. Those include the manufacturer’s name or brand, the trade description, the tyre-size designation, an indication of structure, the speed-category symbol, the load-capacity index, the word “TUBELESS” where applicable, and the words “REINFORCED” or “EXTRA LOAD” where the tyre is a reinforced tyre.
Each required marking must be moulded onto or into the tyre, must be clearly legible, and—except for the manufacturer’s name—must sit in the lower half of at least one sidewall.
ADR 96/00 requires a comparable list for commercial tyres and adds several markings that are directly relevant to towing:
| Marking | What the standard says it means |
|---|---|
| Four-digit date code | Week and year of manufacture |
| “LT” prefix, or “C” / “LT” suffix | Light truck or commercial tyre designation |
| “FRT” | Free Rolling Tyre — designed for trailer axles and for axles other than front steering and drive axles |
| “CP” suffix | Tyres on 5° drop centre rims with a single load-capacity index of 121 or less, specifically designed for motor caravans |
| “REGROOVABLE” or the regroove symbol | The tyre may be re-grooved |
| “M+S”, “M.S” or “M&S” | Snow tyre, or a special-use tyre declared as also meeting that definition |
The “CP” marking is worth flagging because of its name. Under ADR 96/00 it identifies tyres designed for motor caravans—motorhomes—not for towed caravans or camper trailers. “FRT” is the marking that refers to trailer axles.
What the rules do not say
Three absences matter more than they might appear.
There is no clause in ADR 95/00 requiring the sum of a trailer’s tyre load capacities to equal or exceed a stated mass. The arithmetic sum requirement in clause 5.1.2—that the sum of the load carrying capacities of all tyres must not be less than GVM—is written for L-group vehicles, that is, mopeds, motorcycles and motor tricycles. For T-group vehicles the requirement is the qualitative one at clause 5.3.1: the tyres must be suitable for the model or type with respect to dimensions, speed and load performance.
There is no placard requirement for TC and TD trailers in ADR 42/05 clause 20.1.
And none of these standards is an in-service rule. The ADRs are national road vehicle standards applied at manufacture and certification. What a registered trailer must have on the road is set by your state or territory road authority.
That distinction is why an ADR citation cannot settle a roadside question on its own, and why the trailer’s own placard and the manufacturer’s documentation remain the starting point.
Replacing trailer tyres
Transport for NSW publishes Vehicle Standards Information No. 9, revision 5, dated 28 February 2019, covering the fitting of alternative wheels and tyres. Its load-rating rule is plain: all replacement tyres must have a load rating equal to or higher than the rating of the original tyres fitted by the vehicle manufacturer, and that information is available from the tyre placard or from the manufacturer.
On speed, the same document says the rating of tyres fitted should be equal to or higher than the original, with a qualified exception where the specified rating is above 180 km/h, and it recommends a warning label where a lower-rated tyre is fitted. It also confirms that retreaded tyres must comply with AS 1973–1993, and that regrooved tyres must not be fitted unless the tyre was constructed with extra rubber for that purpose and labelled accordingly.
The document uses load-capacity index 62 as its worked example, giving 265 kg—the same value published in ADR 23/03 Annex 4 and ADR 96/00 Annex 4.
One caveat we will not paper over: VSI.09 is written around vehicles with a driver-accessible placard in the glove box, engine bay or door pillar, and it does not address trailers separately. Treat it as the principle a road authority applies to replacement tyres, and confirm the requirement for a registered trailer with the road authority in your own state or territory.
A checklist before you tow
Work from documents and markings, not from recollection:
- read the load-capacity index and speed symbol on each tyre, including the spare;
- convert the index using the table published in ADR 23/03 or ADR 96/00 Annex 4, not a third-party chart;
- compare those figures with the trailer’s tyre placard, if it is a TA or TB trailer;
- confirm that a replacement matches or exceeds the placard’s load rating;
- check the four-digit date code on every tyre, spare included;
- confirm the tyre class is the one the trailer was built around—C1 against C2 or C3;
- record the cold inflation pressure the placard specifies, and set the tyres cold;
- check for markings that reveal a purpose, such as FRT for trailer axles.
Then check the mass side of the equation. The tyres support the trailer’s own wheel loads, which is the GTM side of the calculation rather than the coupling side; our guides to payload as ATM minus tare and to towball download and vehicle payload set out how those figures interact.
A tyre marking is evidence of what a tyre was approved to do. A weighbridge ticket is evidence of what you are asking it to do. Compliance lives where the two meet, and neither number can be assumed from the other.