SUV Tyre Legal Limits

SUV tyres are versatile — but they have limits. Here’s what every driver should know.

Fast Facts

• The legal minimum tread depth for SUV tyres is 1.6 mm – you must replace tyres by this point.

• Check your speed rating index to know the tyre’s maximum safe speed.

• Always confirm your load index, which indicates how much weight your tyre can carry.

• Tyres should be no more than 10 years old, even if they appear in good condition.

Understanding SUV Tyre Limits

SUVs are built for versatility — from family trips on the highway to off-road adventures.
But no matter how capable your vehicle, your tyres have defined safety and performance limits.
Knowing these limits isn’t just about compliance with legal requirements — it’s about maximising tyre life, vehicle handling, and your safety on every journey.

The four key areas to monitor are:

1. Tread depth

2. Speed rating

3. Load index

4. Tyre age

Let’s explore each in more detail.

1. Tread Depth — Grip and Safety

The legal minimum tread depth for road tyres is 1.6 mm, and this applies to most SUVs and crossovers.
However, tyre performance begins to deteriorate well before it reaches that point — particularly in wet or snowy conditions.

• On wet roads, shallow tread increases the risk of aquaplaning, as water cannot escape effectively.

• On snowy or icy roads, braking distances lengthen and traction decreases dramatically.

Tip: Check your tyres regularly and consider replacing them early for improved safety in adverse conditions.

4x4 and Off-Road SUVs

For SUVs equipped with 4x4 capability or off-road tyres, tread depth plays an even more critical role.
These tyres often start with up to 20 mm of tread, but their performance drops sharply once worn.
Worn tread shoulders or flattened blocks can severely reduce grip on mud, grass, gravel, and snow.

Use the Tread Wear Indicators (TWI) — small raised bars inside the grooves.
If these bars are level with the tread surface, your tyre has reached its wear limit and must be replaced immediately.

2. Speed Rating — Maximum Safe Speed

Every tyre has a speed rating, shown as a letter on its sidewall (for example, H, T, or S).
This rating indicates the maximum speed the tyre can safely sustain under its specified load.

For off-road SUVs, it’s normal to have a lower speed index (often between Q and S), since these tyres prioritise durability and load-carrying capacity over top speed.
By contrast, on-road SUV tyres usually start from a T rating or higher.

Reminder: Even if your tyres are rated for high speeds, always follow local speed limits and drive according to conditions.

3. Load Index — How Much Weight Your Tyres Can Carry

SUVs are heavier than standard cars and often carry more passengers, luggage, or even tow trailers — so load capacity matters.

The load index (a two- or three-digit number) specifies the maximum weight each tyre can safely support when fully inflated.
You’ll find this number on the tyre’s sidewall — for example, in 235/60 R18 107V, the “107” is the load index.

• A higher number means a greater load-carrying capacity.

• This capacity reduces if tyre pressure drops, so always maintain correct inflation levels.

• You can find the manufacturer’s recommended load index and pressure in your vehicle manual or on the driver’s door pillar.

This information is particularly important for towing caravans, trailers, or carrying heavy loads — exceeding your tyre’s load limit can cause overheating, blowouts, or premature wear.

4. Tyre Age — Knowing When to Replace

Even if your tread depth and tyre condition seem fine, age matters.

On-road and Crossover SUVs

• Tyres should be replaced every 10 years at the latest, including the spare.

• Regular inspection is essential to spot signs of ageing such as cracking, deformation, or hardening rubber.

Off-road SUVs

• Replace tyres at least every 5 years if used regularly on rough terrain.

• Off-road tyres experience higher stress and wear due to heavy loads, sharp rocks, and temperature fluctuations.

• After 5 years, have your tyres professionally inspected annually, even if they appear intact.

Pro tip: Off-road driving accelerates tyre ageing — regular cleaning, correct pressure, and rotation will extend lifespan.

Staying Safe and Legal

Adhering to SUV tyre limits is crucial for both performance and compliance.
Ignoring tread depth, load, or age recommendations can compromise traction, braking, and cornering — especially in challenging conditions.

Quick checklist for SUV owners:

• ✅ Tread depth above 1.6 mm (ideally more for wet conditions)

• ✅ Correct speed and load index for your vehicle

• ✅ Tyres inspected regularly and replaced before 10 years old

• ✅ Pressure maintained to manufacturer specifications

• ✅ Replacement tyres installed in matched pairs or full sets for even handling

Final Thought

Your SUV’s tyres are the only point of contact between your vehicle and the road.
Respecting their legal and technical limits isn’t just about obeying the law — it’s about ensuring safety, performance, and peace of mind every time you drive.

Drive smart. Stay safe. Replace on time.