Truck tire size lookup

Pick your make, model and year above and this tool returns the tire sizes that truck was sold with from the factory, along with the wheel sizes they were fitted to. The authoritative source for your specific truck is the placard on the driver's door jamb, because the size depends on trim and wheel package as well as model year.

The 265 is the section width in millimetres — the widest point of the tire, not the tread. The 70 is the aspect ratio: the sidewall height is 70 per cent of 265 mm, so about 186 mm or 7.3 inches. The R means radial construction. The 17 is the wheel diameter in inches. Add two sidewalls to the wheel diameter and you get the overall diameter — about 31.6 inches for a 265/70R17.

On the placard sticker inside the driver's door jamb. It lists the original tire sizes front and rear and the cold inflation pressures for them. The size moulded on the tire sidewall tells you what is fitted now, which is not always the same thing on a used truck.

As a rule of thumb, most pickups take one size up — roughly 3 per cent more overall diameter — on stock suspension without rubbing. Beyond that you are usually into trimming the front bumper valance, adjusting the wheel stops, or a levelling kit. The exact answer depends on offset as much as diameter: a wider tire on a lower offset pushes toward the fender liner long before diameter becomes the problem.

Yes, in proportion to the change in overall diameter. A tire 3 per cent taller makes the speedometer read about 3 per cent low, so an indicated 70 mph is really about 72. It also affects the odometer, the trip computer's mileage figures and, on some trucks, shift points and the ABS. Staying within 3 per cent keeps all of that inside its normal tolerance; going further usually means recalibrating.

On a four-wheel-drive truck, yes — mismatched rolling diameters make the transfer case and differentials fight each other, which is expensive. Even on a two-wheel-drive truck, mixing sizes across an axle upsets braking and stability. Replace in axle pairs at minimum, and in full sets on any four-wheel drive.

It is a coded number for the maximum weight one tire can carry at its rated pressure. Trucks also use load range letters — C, D, E — which describe how much air pressure the tire is built to take and therefore how much it can carry. If your placard calls for load range E and you fit load range C, the tire is not rated for the truck's axle weight, and it will feel vague under a load even before that becomes a safety issue.

Close, and that is exactly why both conventions exist. A 285/70R17 works out to about 32.7 inches overall, so it is sold and discussed as a 33. Flotation sizes such as 33x12.50R17 state the diameter directly. When you are comparing across the two systems, always convert to overall diameter in inches rather than trusting the marketing name.