Truck Axle Mass Limits in South Africa: Why One Axle Group Can Make You Illegal

You can be inside your total legal mass and still be illegal. That single sentence catches more new operators than any other rule in South African road transport, and it is written into the standard in plain words.

TRH 11 §1.2.2: “When the allowable mass of the vehicle/combination or one or more axle groups exceeds the legal limitations, a mass abnormality exists.”

Axles are how your load reaches the road, and the law limits mass three ways at once: per axle group, by the spacing between axles, and by where the mass sits relative to your steering and drive axles. This guide covers all three, with the regulation behind each one.

1. What each axle may carry

Regulation 240 sets maximum axle mass loads. Three things change the answer: whether the axle steers, whether it runs single or dual wheels, and how many axles are grouped together.

Axle type	Single	Two grouped	Three grouped
Steering axles	7 700 kg	15 400 kg	23 100 kg
Non-steering axles	8 000 kg	16 000 kg	24 000 kg
Axles with dual wheels	9 000 kg	18 000 kg	24 000 kg

Dual wheels are worth 1 000 kg an axle, and that is the practical reason almost every load-carrying axle in the country runs them. Note also that three grouped axles cap at 24 000 kg whether they carry single or dual wheels — the dual-wheel advantage disappears at the tridem.

2. Spacing: the bridge formula

The table above is not the only limit on a group. Regulation 241 adds a second one based on how far apart the axles sit, because a given mass spread over a longer distance is gentler on a bridge deck:

P = 18 000 + 2 100 × L

Where P is the permissible maximum mass of the group in kilograms, and L is the distance in metres from the centre of the group’s first axle to the centre of its last, rounded up to the next tenth of a metre.

Worked example. A trailer tri-axle group at a 1,35 m pitch — the spacing our own equipment drawings use — puts 2 × 1,35 = 2,7 m between the first and last axle centres.

• P = 18 000 + (2 100 × 2,7)
• P = 18 000 + 5 670
• P = 23 670 kg

That is less than the 24 000 kg the axle table allows for three grouped axles. Both rules apply at once, so the lower of the two binds — and on a closely spaced tridem it is the spacing rule, not the axle table, that decides. Spread the same three axles further apart and the formula gives you more.

3. Where the mass sits: the three ratios

Even with every axle inside its limit, the load has to be distributed properly. Three ratios govern this, and they exist for different reasons: one so the vehicle can pull, one so it can steer, and one so it can keep up with traffic.

Traction — drive axles at least 20%

Regulation 239: the mass load carried on the drive axles may not be less than 20 per cent of the total mass of the vehicle or combination. Too little weight over the drive axles and the truck cannot get traction — on a wet gradient that is not a paperwork problem, it is a stuck or sliding truck.

Steering — and the number depends on your vehicle

Regulation 242 sets a minimum for the steering axle, and the percentage is different for different vehicles:

Vehicle	Steering axle must carry at least
Truck-tractor with at least one semi-trailer	11% of the truck-tractor plus first semi-trailer
A motor vehicle with a steering axle unit (not the above)	30% of that vehicle’s total
Any other vehicle	20% of that vehicle’s total
Agricultural tractor	12%

This is the rule that punishes a badly placed load. Put the cargo too far back on the trailer and weight lifts off the steering axle. The weighbridge total can be perfectly legal while the front of your truck has gone light — which is an offence, and long before it is an offence it is a vehicle that does not steer properly in a crosswind or an emergency swerve.

Power to mass — the ceiling on what you may pull

Also Regulation 239: permitted mass in kilograms may not exceed the engine’s net power in kilowatts × 400 where the drawing vehicle is a truck-tractor, or × 240 for any other vehicle. Covered in full in the horsepower guide, but it belongs on this list because it is the third thing that can make a legally loaded truck illegal.

What our own fleet records — and what it does not

Of the 324 real trucks registered on Kweli Load Exchange, here is what we hold on trailer axles:

• 3 axles — 39 trailers
• 2 axles — 17
• 4 axles — 12
• Not recorded — 256

Seventy-nine per cent of the fleet has no axle count on record. We publish that because it is true and because it matters to how you read the rest: three axles is the most common recorded configuration on this network, but it is the most common of a minority. We are not going to project 39 trailers onto 324 and call it a finding.

Watch

• Axle Weights, Performance & Costing For Semi-Trailers & Interlinks (South Africa) — TruckScience. South African, and directly on this subject.

Linked because it is useful and locally relevant to South African operators.

Questions people ask

Can I be overloaded if my total mass is legal?
Yes. TRH 11 states that a mass abnormality exists when the combination “or one or more axle groups” exceeds the limit. One group over is an offence even when the total is under.

What is the maximum axle load in South Africa?
Regulation 240 sets 7 700 kg for a single steering axle, 8 000 kg for a single non-steering axle, and 9 000 kg for an axle with dual wheels. Grouped axles scale from there, with three grouped axles capped at 24 000 kg.

Why do axle spacing rules exist?
Because a bridge deck feels concentrated mass differently from spread mass. Regulation 241 gives P = 18 000 + 2 100 × L, where L is the distance between the first and last axle centres of the group. Both this and the axle table apply, and the lower figure binds.

How much weight must be on the steering axle?
For a truck-tractor with at least one semi-trailer, at least 11% of the combined mass of the truck-tractor and first semi-trailer. Other vehicle types are 30%, 20% or 12% depending on configuration. Under permit the minimum is 15% of the drawing vehicle’s total.

What happens if I load too far back?
Weight comes off the steering axle. You may pass on total mass and still fail the steering ratio — and the vehicle handles badly long before it fails a check.

Where the numbers come from

• Axle mass limits — TRH 11 Figure 3.1, reproducing Regulation 240. Cross-checked against two revisions of the standard, the 8th (Pretoria 2010) and the 2017, because the figure is a diagram and a single extraction of it is not reliable enough to publish from.
• Axle spacing formula — TRH 11 §3.5, reproducing Regulation 241.
• Traction ratio — TRH 11 §3.7.1, reproducing Regulation 239.
• Steering ratios — TRH 11 §3.8.1, reproducing Regulation 242.
• Mass abnormality definition — TRH 11 §1.2.2, quoted verbatim.
• Fleet axle counts — Kweli Load Exchange, real non-test vehicles, read 16 August 2026.
• The 1,35 m bogie pitch in the worked example — the spacing used in Kweli’s own scale equipment drawings. Your trailer’s actual pitch is what belongs in your own calculation.

This is a guide, not a compliance certificate. Regulations are amended; your vehicle’s manufacturer ratings may be lower than the legal maxima, in which case the manufacturer’s figure is the one that binds; and a permit changes the numbers again. Weigh your own truck.

Next

• Trucks for road freight — the hub: body, rig and axles
• Truck configurations — rigid, articulated, superlink and interlink
• Which trailer for which cargo — all 34 types
• Kweli Load Exchange — loads matched to your truck and corridor