265/75R16 — what one aspect-ratio step actually buys

A quiet size with one factory home

Among the vehicles catalogued here, 265/75R16 has exactly one recorded factory fitment: the Nissan Frontier D40, from 2005. That is unusual for a size this ordinary-looking, and it reflects the timing — by the time trucks were being specified with tires this tall, most of them had moved past the 16-inch wheel.

Two metric sizes occupy the 31-to-32 inch band on a 16-inch wheel

That is the whole list: this size at 31.65 in, and 235/85R16 at 31.73 in. They are 0.08 in apart — a quarter of a percent, invisible on any instrument — and 1.18 in apart in section width.

So on a 16-inch wheel, choosing a tire "just under 32 inches" is not really a choice about height at all. It is a choice between a 10.43 in casing and a 9.25 in one, and the two look nothing alike on the vehicle while producing speedometer readings that differ by less than a third of a mile per hour at 70.

Why five aspect points is always 1.04 in here

Aspect ratio is a percentage of section width, so the diameter change from an aspect step depends on the width and on nothing else. For a 265, five points is 13.25 mm of sidewall, doubled for the two sides, which is 26.5 mm — 1.04 in.

That figure holds on every wheel diameter. 265/70R16 to 265/75R16 is +1.04 in. So is 265/65R17 to 265/70R17, and so is 265/60R18 to 265/65R18. The wheel cancels out because it appears identically on both sides of the subtraction.

It is worth internalising because it turns the question "how much taller" into arithmetic that can be done without a calculator, provided the section width is not also changing. When the width does change, the shortcut breaks immediately — which is the next section.

Twenty millimetres of width, in both directions

Hold the 75 aspect ratio and move the first number instead:

Size	Section width	Diameter	Change
245/75R16	9.65 in	30.47 in	−1.18 in (3.73%)
265/75R16	10.43 in	31.65 in	—
285/75R16	11.22 in	32.83 in	+1.18 in (3.73%)

Twenty millimetres of section width at 75 aspect is 15 mm of sidewall per side, 30 mm across the tire, 1.18 in of diameter. The steps are symmetrical, and both are larger than the aspect step from the previous section — which is the counter-intuitive part, since a 20 mm change in width sounds smaller than a five-point change in shape.

Going down to 245/75R16 makes an indicated 70 mph an actual 67.4 mph. Going up to 285/75R16 makes it 72.6 mph.

The flotation size below it

31x10.50R16 measures 31.00 in and 10.50 in wide. Against this size that is 0.65 in shorter and 0.07 in wider — the rare case where the flotation tire is both shorter and fatter than its metric neighbour. If a set of 31s is being compared against a set of these, the height difference is 2.05% and the width difference is negligible.

Above, 33x12.50R16 sits at 33.00 in: +1.35 in, +4.27%, and a full 2.07 in of extra section width.

Where it sits on the one truck that came with it

The Frontier D40's record is a useful illustration because it contains almost this entire page in one line. Its factory sizes are 265/70R16, 265/75R16 and 265/65R17 — the first two being the aspect step described above, the third being the same tread width moved onto a bigger wheel. Its listed upgrades are 285/75R16, 285/70R17 and 33x12.50R16, which are the width step, the width step on a 17-inch wheel, and the flotation 33 respectively.

Read down that list and every move available on the truck is one of three operations: change the aspect ratio, change the section width, or change the wheel. Each has its own fixed cost in inches, and the three do not combine intuitively.

Two of those operations nearly cancel

Take this size, drop five aspect points, and add an inch of wheel. The first move costs 1.04 in of height. The second returns 1.00 in. The result is 265/70R17 at 31.61 in, which is 0.04 in shorter than this tire — 0.14%, an error a speedometer could not express if it wanted to.

That is worth holding onto, because 265/70R17 is one of the most widely fitted sizes in North America and this one is nearly extinct. A driver moving off a 16-inch wheel onto the size the rest of the market standardised on is, in every respect these calculations can see, keeping the same tire. The section width does not move either: both are 10.43 in.

What does move is 0.52 in of sidewall per side, transferred into wheel. The 0.04 in of height is a rounding artefact of two operations that were never designed to cancel and happen to.