Most SUVs on UK roads use ordinary metric tyre sizes, read exactly like any car tyre. But heavier 4x4s, pickups and imported or modified vehicles can carry markings that car tyres never do, so it helps to know what they mean.
Standard metric: the common case
The large majority of SUVs and soft-roaders use a standard metric size such as 235/65 R17, where the numbers mean width, profile and wheel diameter just as they do on a car. For these vehicles, reading the size is no different from reading a hatchback's, and the same rules on load index and speed rating apply.
When a 4x4 needs more
Heavier and more capable vehicles can need a stronger tyre than the standard passenger build, and three markings signal this:
- The C (Commercial) rating, on heavier 4x4s and pickups used for load-carrying, with its own dual load index
- The LT (Light Truck) system, a North American designation
- Imperial flotation sizes, common on off-road tyres
The LT marking
LT stands for Light Truck and appears before the size, as in LT265/70 R17. It is a North American system for tyres built to carry heavier loads and take off-road punishment. LT tyres carry a load range letter (such as C, D or E) and usually a dual load index, and they are tougher in construction.
That strength comes with trade-offs: LT tyres tend to ride more firmly, weigh more and can use more fuel than a standard tyre. They suit vehicles that genuinely tow, carry or go off-road, rather than a road-biased SUV.
P-metric and Euro-metric
A size may also carry a P prefix (US passenger) or none at all (European metric). The two are dimensioned the same way, but their load capacities are calculated differently, and a passenger-rated tyre fitted to a heavier vehicle is rated more conservatively. The practical rule is to match the rating on the vehicle's placard rather than assume one size fits.
Matching the vehicle
Whatever the system, the principle holds: the size, the load rating and the category must match what the vehicle requires. A heavy 4x4, or one used for towing or off-road work, needs the specified load capability, and changing the overall size also affects the speedometer reading, ground clearance and handling. The door placard and handbook are the reference for what a particular 4x4 needs, and when the time comes to replace them, a registration search on the tyre-buying site Tyres.co.uk brings up the options in the right size, load rating and category for the vehicle.
From the workshop: people with road-going SUVs often worry they need something heavy-duty when standard metric tyres are exactly right. The ones who do need LT or commercial tyres are towing, carrying or going off the road, and their placard says so. We fit to the placard, not to the look of the car.
Sources and accuracy. The metric, C, LT and P-metric systems described here reflect standard tyre sizing at the time of writing. The definitive size, load rating and category for a specific vehicle are on its placard and in the handbook. If anything here looks wrong, get in touch and we will check it and put it right.
Common questions
Are 4x4 and SUV tyre sizes different from car sizes?+
Most SUVs use ordinary metric sizes, such as 235/65 R17, read exactly like a car tyre size. Some heavier 4x4s and pickups use a commercial C rating, the US light-truck LT system, or imperial flotation sizes instead.
What does LT mean on a 4x4 tyre?+
LT stands for Light Truck, a North American system shown before the size, as in LT265/70 R17. LT tyres are built tougher for load and off-road use, carry a load range letter and often a dual load index, and ride more firmly than standard tyres.
What is the difference between P and no prefix on a tyre size?+
A P prefix marks a US passenger tyre, while no prefix is a European metric size. They are sized the same way, but the load ratings are calculated differently, so the safest approach is to match the rating on the vehicle's placard.
Can I fit any size tyre to my 4x4?+
No. The size, load rating and category must match what the vehicle requires, shown on its placard. A heavy 4x4 or one used for towing or off-road needs the specified load capability, and changing size affects the speedometer, clearance and handling.