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Tire sizes

30x9.50R15 — the narrowest flotation size here

The bottom rung of the 15-inch flotation ladder, and the one that is narrower than the metric sizes it sits beside.

Flotation (imperial) notation · Flotation (imperial)

Overall diameter
30.00 in
762 mm
Section width
9.50 in
241 mm
Sidewall height
7.50 in
191 mm
Aspect ratio
78.9%
sidewall as a share of width
Wheel diameter
15 in
the hole in the middle
Circumference
94.2 in
2394 mm
Revolutions per mile
672.3
geometric, not measured
Revolutions per km
417.7
geometric, not measured
Typical load index
108–128
2205–3968 lb per tire

Flotation sizes are almost always LT construction, so they share the light-truck band. Speed symbols run low because the aggressive tread patterns these sizes are sold in are rated against heat build-up, not against sustained high speed.

The load-index range shown is the band this CLASS of size is typically produced in — not a list of what is in stock for this exact size today. Load index and speed symbol are printed on the sidewall of the specific tire you are holding, and the required minimum is on the placard of the specific vehicle you are fitting. Read both.

Nearest real sizes in metric notation, same wheel

  • 235/75R1528.88 in tall-1.12 in
  • 225/75R1528.29 in tall-1.71 in
  • 215/75R1527.70 in tall-2.30 in

Compare any two sizes, including ones this site has no page for, in the comparison tool.

Platforms recorded with this size

The Jeep Cherokee XJ is the only vehicle recorded here with 30x9.50R15 among its common upgrades. Nothing ships it.

Narrower than most of what shares its wheel

Flotation codes have a reputation for being the wide option. This one is not. At 9.50 in of section it is slimmer than every other imperial code catalogued, and on its own wheel it is wider than only the smallest metric sizes:

Size Diameter Section width
215/75R15 27.70 in 8.46 in
225/75R15 28.29 in 8.86 in
235/75R15 28.88 in 9.25 in
30x9.50R15 30.00 in 9.50 in
31x10.50R15 31.00 in 10.50 in

Against 235/75R15 — the tallest metric size on a 15-inch wheel here — it is 1.12 in taller and a quarter of an inch wider. Most of what it offers over the metric codes is height, not stance, which is the reverse of the usual flotation proposition.

Thirty inches, found on four other wheels

Five metric codes compute to within 0.06 in of 30.00 in, and not one of them uses a 15-inch wheel: 255/70R16 at 30.06 in, 255/65R17 at 30.05 in, 255/60R18 at 30.05 in, 235/65R18 at 30.03 in and 255/55R19 at 30.04 in.

Read down that list and the pattern is the tire industry's answer to the same problem, restated once per wheel diameter. This size solves it with 7.50 in of casing on a 15-inch rim; the 19-inch entry solves it with 5.52 in on a rim four inches larger. Both roll 30 in of tire and neither knows the difference. What separates them is set out in the plus sizing reference.

The rungs above

Each step up the 15-inch flotation ladder from here adds an inch of diameter and an inch of section width at the same time: 31x10.50R15 at 3.33%, 32x11.50R15 at 6.67%, 33x12.50R15 at 10.00%. The first of those is treated in a direct comparison.

There is no way to buy height on this wheel without buying width with it, which is a constraint of what was produced rather than of the notation.

Related

Class: Flotation (imperial). Every figure above is computed from the size code, not stored — see how these numbers are calculated.