Tyre Dispatch · Workshop Data

Load Ratings and Load Capacity

Every tyre carries two numbers defining what it may do: how much weight it can carry, and how fast it can go. Across 1,540 tyres those numbers trade against each other, decide the shape of the tread, predict how the tyre will be mis-inflated - and expose one widely used marking that turns out to mean almost nothing at all.

Tyre Dispatch, New Zealand · First edition · 29 July 2026 · 1,545 workshop inspections, 1,540 carrying a readable load index and speed rating

The load index is a code, not a weight. A tyre marked 94V is telling you two things: index 94, which the ISO table converts to 670 kg per tyre, and V, permitting 240 km/h. Neither is a recommendation. Both are ceilings, and both are structural facts about how the casing was built.

We read those markings off every tyre through the workshop, photograph them, and store them alongside the measured tread. That gives 1,540 records in which the promise a tyre made can be set against what actually became of it.

FINDING 01Load and speed are a trade, and the cheap seat is in the middle

A casing can be built to carry weight or to tolerate heat and speed. Doing both costs money, so most tyres are built for one.

Capacity falls by more than half from Q to H - 1,285 kg down to 615 kg - then climbs again through V, W and Y. The curve has a floor, and the floor sits at H.

The low-speed end is light-truck and commercial rubber: heavy casings built to carry and never intended to hurry. The bottom at H is the ordinary passenger tyre - the cheapest useful thing to fit to a family car. Past that, W and Y rubber goes on heavy, fast, expensive vehicles, so capacity has to climb back up to hold a two-tonne performance saloon.

FINDING 02Ply rating means almost nothing

Plenty of tyres are still sold and discussed by ply rating - 6-ply, 8-ply, 10-ply. The term survives from an era when it counted actual layers of cotton in the casing. It has not described construction for decades, and in this fleet it does not reliably describe capacity either.

Every one of our fifteen 6PR tyres carries more than the weakest 8PR. The lightest 8-ply is rated 560 kg; the lightest 6-ply is 800 kg. A 6-ply tyre out-carrying an 8-ply by 240 kg is not an exception in this data - it is the norm, because the ranges overlap across almost their entire length. The same is true one step up: the strongest 8PR at 1,500 kg beats every 10PR below index 122.

Anyone buying "an 8-ply tyre" expecting a capacity guarantee is buying a word. The load index is the only marking that carries a defined, testable meaning, and it is printed on the same sidewall.

Ply rating is recorded on 130 records - it appears almost exclusively on light-truck and commercial tyres, which is where the term persists in the trade. Those are also, notably, the tyres whose buyers are most likely to be carrying something.

FINDING 03Extra Load has quietly become the default, and it is not about load

An XL or Reinforced marking means the casing is rated to carry more at a given size than its standard equivalent. It sounds like a heavy-duty option. In this fleet it behaves like something else entirely.

Eight per cent of H-rated tyres are XL. Eighty per cent of W-rated ones are. The marking tracks which vehicles go fast, not which carry weight - and comparing what the two groups actually hold shows why that matters:

An XL tyre here carries almost exactly what a standard one does - 710 kg against 690 kg. The marking is not buying capacity. It compensates for construction: a short, wide, low-profile sidewall on a big rim has less air volume and less flex, so it needs a reinforced casing simply to reach the rating an ordinary 65-profile manages without one. XL is the price of the wheel fitted to the car, not an upgrade to it.

XL has gone from one tyre in ten to nearly one in two in a little over a decade - while median capacity never moved. Nothing is being asked to carry more. Wheels grew, profiles shrank, and the reinforced casing went from a speciality to the ordinary way of building a tyre for a modern car.

FINDING 04Speed rating decides the shape of the tread

Tread patterns come in three architectures: symmetrical, which is the same across the width and can be rotated anywhere; asymmetrical, with a different pattern inboard and outboard; and directional, which must turn one way. Which one a tyre gets is almost entirely settled by its speed rating.

The transition is close to perfectly ordered. Not one R-rated tyre in the set is asymmetric. Not one Y-rated tyre is symmetric. Everything in between moves smoothly from one to the other as the permitted speed climbs.

Load rating shows the same pattern - above index 110 the fleet is 95% symmetrical, and above 120 it is 97% - but we checked whether that is really about load, and it mostly is not. Held within a single profile band, load index barely moves the mix until the very top. Aspect ratio is the stronger driver: asymmetric patterns account for 72% of ultra-low-profile tyres, 42% of low, 16% of mid and just 6% of high-profile. Speed rating and profile are describing the same performance fitment; load rating is correlated because heavy-duty tyres happen to be slow-rated.

There is a practical consequence. Symmetrical tread can be rotated to any corner of the vehicle; asymmetric and directional cannot be moved as freely. The fitments most prone to alignment wear - low-profile, high-speed-rated - are also the ones whose rotation options are most restricted, which removes the cheapest available remedy for uneven wear from exactly the tyres that need it most.

Ply rating tells the same story from the commercial end: all 59 of our 8PR tyres are symmetrical, as are 96% of 10PR. Load-carrying tyres are effectively never asymmetric.

FINDING 05Load rating predicts how a tyre will be mis-inflated

Our companion report on inflation found under-inflation dominating passenger cars and over-inflation dominating light trucks. Load index turns out to be the sharpest single predictor of that split in the whole dataset - sharper than construction, width or terrain.

The gradient runs the full length of the scale. In the lowest band under-inflation outruns over-inflation five to one. By the top band it has inverted entirely: not one tyre rated 120 or above showed under-inflation wear, and 72% showed the opposite.

A high load index means a casing designed to be inflated hard because it expects weight. When the vehicle runs empty - as utes, vans and trailers mostly do - that pressure far exceeds what the load needs, the centre of the tread carries everything, and it scrubs out while the shoulders are barely touched.

FINDING 06Certification coverage rises with load rating

Not one tyre rated 1,400 kg or above lacked a certification mark. Nearly 7% of the lightest ones did. The heavier the tyre, the more likely somebody along the chain has checked it - which is reassuring in one direction and less so in the other, since the unmarked tyres are concentrated at the small, cheap, high-volume end of the market.

One group stands apart: 25 tyres carry CCC and SNI but no E-mark, at a median index of 109 (1,030 kg). That is commercial rubber approved for the Chinese and Indonesian markets and never put through European type approval - legal to sell here, but certified against a different standard than most buyers would assume.

FINDING 07The failure curve peaks in the middle of the range

Ordinary passenger tyres fail most. The 90–99 band - the largest group at 609 records, and the default fitment on the default car - fails at 53%, about twice the 110–119 band at 27%. Part of that is how they are used up:

Only 13% of the 110–119 band reached the legal limit anywhere, against 25% of the 90–99 band. Heavier-rated tyres are more often replaced for some other reason - damage, a set change, a vehicle sale - while ordinary passenger tyres get run until they are finished.

FINDING 08Fast tyres fail more, and fail younger

W and Y-rated tyres fail at 58% and 60% against 34% for T - and they are a full year younger when we see them, at a median 4.5 years against 5.5. They are not failing on age; they are being used up faster. Soft high-grip compounds wear quickly by design, and these tyres sit on the low-profile fitments that carry roughly double the fleet rate of alignment wear.

FINDING 09What the fleet can actually carry

The median set is rated at 2,760 kg. A typical light passenger car has a gross mass around 1,800–2,200 kg, so the ordinary fitment carries a comfortable margin. The tail matters more than the middle: 17.2% of tyres are rated below 2,200 kg across a set, leaving little headroom on a fully loaded small car.

FINDING 10Testing the markings against the actual rule

New Zealand's in-service inspection requirements are specific enough to test directly. The VIRM section on tyres and wheels sets conditions on load index, speed rating and marking legibility, and we hold all three for every record.

The clean result is the speed rating. Not one tyre in 1,540 was rated below the open-road speed limit - the lowest rating present anywhere in the programme is Q, at 160 km/h. Whatever else is wrong with the fleet, this is not.

The load-index result needs care and we will not overstate it. The rule applies to tyres on the same axle, and we do not record which corner a tyre came from. A set reading 102/102/98/98 is entirely compliant if the matched pairs sit on separate axles - and two of our ten flagged sets look exactly like that. These are candidates for investigation, not confirmed breaches. What can be said is that a spread wide enough to matter appears in roughly one set in forty, and mixed speed ratings in about one in fifteen.

Other patterns worth recording

Two of these are worth pulling out. Soft performance compounds carry the highest XL rate in the dataset at 66% - reinforcement is effectively standard equipment on short-life grip rubber. And UTQG temperature grade B tracks load, not heat resistance: grade B tyres sit at a median 1,060 kg against 670 kg for grade A, because grade B is where the commercial casings live. Our inflation report saw grade B behaving differently and correctly declined to call it a temperature effect; this is the reason.

Brand-level differences are large - median load index ranges from 89 to 111 across brands with 25 or more records - but they reflect which market a brand sells into rather than how good its tyres are. A brand supplying four-wheel-drive and commercial fitments will show a high median by definition. We have not published a brand table, because a ranking by load index would be read as a quality ranking and it is not one.

A note on the data itself

Two things we expected and did not find. There are no retreads in 1,545 records - routine in a commercial fleet, entirely absent here. And genuinely mismatched fitments are rare: only 8 tyres pair a W or Y speed rating with a load index below 85, all small performance sizes where that combination is normal rather than wrong.

Tyre Dispatch · New Zealand · First edition · 29 July 2026
Descriptive analysis of one workshop's records. Not a representative sample of the national fleet, and not a substitute for a warrant of fitness inspection. Load index and speed rating are maximum ratings at the tyre's specified inflation pressure; the correct pressure and minimum ratings for any vehicle are set by its manufacturer. Inspection requirements summarised from the NZTA Vehicle Inspection Requirements Manual, in-service WoF and CoF, section 10-1 Tyres and wheels. Corrections welcome: email@tyredispatch.co.nz
Page © 2026 Tyre Dispatch NZ · Dataset, measurements and photographs © Taylor Houghton, all rights reserved · Dataset licensing