33x10.50R17 — the 33 that five mid-size trucks list

Five vehicle records here list 33x10.50R17 as a common upgrade: three mid-size pickups, an SUV built on one of them, and a fourth pickup from a different manufacturer. They are listed with the computed figures. None ships it.

That concentration is the interesting fact about the size. The wide 33 on the same wheel appears on one vehicle's upgrade list; this one appears on five, and all five are the same class of vehicle.

The narrow 33 in proportion

10.50 in of section under 8.00 in of sidewall gives a derived aspect ratio of 76, which is the tallest proportion of any 33 in this catalogue. The wide version on the same wheel works out at 64, and the 20-inch one at 52.

Nothing on a flotation tire prints that figure, so a buyer choosing between two codes that both say 33 has no way to see that one is shaped like a light-truck 75-series casing and the other like a 65-series one. The aspect ratio reference sets out how the number is derived and why it is worth deriving.

The size it is almost indistinguishable from

265/75R17 matters more than anything else nearby, because several of the trucks that list this size are delivered on 265-width tires already. It measures 32.65 in against this tire's 33.00 in and 10.43 in across against 10.50 in — 0.35 in of height and seven hundredths of an inch of width.

At that separation the choice between them is a choice of tread pattern and construction, not of dimensions. Nothing on the vehicle can tell them apart.

Three widths, all within half an inch of 33 inches

255/80R17 is the third code in this neighbourhood, six hundredths of an inch taller than this size on a casing 0.46 in narrower. Put the three together — 10.04 in, 10.43 in and 10.50 in — and the 33-inch mark on a 17-inch wheel turns out to be reachable across a band of section widths less than half an inch wide.

That is a far finer choice than the argument between the two flotation 33s implies, and it exists only because metric codes fill in the gaps that whole-inch notation leaves. This size is set against both a common factory tire and its wide namesake in the 265/65R17 comparison and the wide-33 comparison.