Tyre Load Ratings and Speed Ratings Explained (And Why They Matter When Towing)

Every tyre's sidewall carries a load index and a speed rating. In 265/65R17 112T, the “112” is the load index — this tyre can carry 1,120 kg — and the “T” is the speed rating, good for 190 km/h. Replacement tyres must meet at least the ratings shown on your vehicle's placard, and if you tow near maximum loads, that margin matters more than anything else on the sidewall.

How do you read a tyre sidewall?

Take 265/65R17 112T: 265 is the width in millimetres, 65 the sidewall height as a percentage of width, R radial construction, 17 the rim diameter in inches — and the final pair is what this article is about: 112 = load index, T = speed rating. An “LT” prefix (light truck) marks a stiffer carcass built for higher loads at higher pressures — common on serious 4WD rubber.

Load index: what the numbers mean

The load index is a code for the maximum weight one tyre can carry at its rated pressure. Common values:

• 100 = 800 kg per tyre

• 104 = 900 kg

• 108 = 1,000 kg

• 112 = 1,120 kg

• 116 = 1,250 kg

• 120 = 1,400 kg

Multiply by the tyres on an axle and compare against your axle load — that's the safety margin you're actually running. A pair of 112-rated tyres offers 2,240 kg of capacity; load the axle to 2,000 kg and you're using nearly 90 per cent of it, every kilometre.

Speed ratings: what the letters mean

• N = 140 km/h · common on some LT and van tyres

• Q = 160 km/h · typical mud-terrain territory

• S = 180 km/h

• T = 190 km/h · most passenger and touring tyres

• H = 210 km/h

• V = 240 km/h · performance cars

With a 110 km/h national limit, the letter isn't about how fast you'll drive — it's a heat-capacity rating. A higher letter means more margin when the tyre is hot, loaded and working hard.

Why do ratings matter most when towing?

Hitch a van and three things stack against your tyres: ball weight loads the rear axle, the van's own tyres run near their maximum, and everything runs hotter for longer. Heat is what kills tyres — an overloaded or under-inflated tyre fails from the inside out with little warning. Check the load index on the van's placard against its ATM, keep pressures matched to the actual load (our caravan pressure guide shows how), and consider live pressure and temperature monitoring — rising temperature on one tyre is the earliest visible sign of an overload or bearing problem.

Frequently asked questions

Can I fit a higher load index than my placard specifies?

Yes — equal or higher is the rule. Going up an index adds margin; going below the placard rating makes the vehicle unroadworthy in every Australian state.

Does speed rating really matter if I never exceed 110 km/h?

It still matters. The rating reflects sustained heat tolerance, and a loaded tyre on a 40°C day at 100 km/h works nearly as hard as an unloaded one at far higher speed. Never fit below placard specification.

What's the difference between XL and standard tyres?

XL (extra load) tyres use a reinforced carcass that carries more weight at higher inflation pressure — useful for loaded touring wagons and utes. They need those higher pressures to deliver the rating, so set them by the load tables, not habit.

Not sure what your rig is really carrying? Call 0448 626 964 — the Flatmate team talks axle loads and pressures all day, no call centre script involved.