33x12.50R18 — a 33 with the casing depth of a 35
The height says 33 and the casing depth says something else entirely.
Flotation (imperial) notation · Flotation (imperial)
- Overall diameter
- 33.00 in
- 838 mm
- Section width
- 12.50 in
- 318 mm
- Sidewall height
- 7.50 in
- 191 mm
- Aspect ratio
- 60.0%
- sidewall as a share of width
- Wheel diameter
- 18 in
- the hole in the middle
- Circumference
- 103.7 in
- 2633 mm
- Revolutions per mile
- 611.2
- geometric, not measured
- Revolutions per km
- 379.8
- 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
- 275/70R1833.16 in tall+0.16 in
- 265/70R1832.61 in tall-0.39 in
- 285/65R1832.59 in tall-0.41 in
Compare any two sizes, including ones this site has no page for, in the comparison tool.
Platforms recorded with this size
Two vehicles here list 33x12.50R18 as a common upgrade: the 200-Series Land Cruiser and the L663 Land Rover Defender. Both are heavy, premium, factory-equipped with 18-inch wheels, and neither ships this size.
Same casing depth as a tire two inches taller
Subtract the wheel from the tire and halve the result: 7.50 in. Now do the same for 35x12.50R20 — also 7.50 in.
A 35 on a 20-inch wheel and a 33 on an 18-inch wheel put exactly the same amount of rubber between the rim and the road, on exactly the same 12.50 in of tread width, and differ by 2.00 in of standing height. Everything people associate with the difference between a 33 and a 35 — how far the tire rolls, what the speedometer reads, what the axle ratio is working against — is in that 2.00 in, and none of it is in the casing.
The two also share a derived aspect ratio of exactly 60, which follows from sharing both the sidewall and the section width. Written in metric notation they would look like the same shape, because in every respect except overall diameter they are.
The 18-inch imperial ladder, in full
| Size | Diameter | Sidewall | Against 33x12.50R18 |
|---|---|---|---|
| 33x12.50R18 | 33.00 in | 7.50 in | — |
| 35x12.50R18 | 35.00 in | 8.50 in | +2.00 in (6.06%) |
| 37x12.50R18 | 37.00 in | 9.50 in | +4.00 in (12.12%) |
Three sizes, one width, two-inch steps, and each rung adds exactly half an inch of casing per side because the wheel is not changing. It is the tidiest flotation range on any wheel diameter here, and this size is the bottom of it.
The metric codes it displaces
275/70R18 is 0.16 in taller at 33.16 in and 1.67 in narrower — the closest thing to this size in metric notation on this wheel, and the subject of a direct comparison.
Below it, 285/65R18 is 0.41 in shorter and 1.28 in narrower, and 265/70R18 is 0.39 in shorter and 2.07 in narrower. All three are within half an inch of this tire in height and between one and two inches narrower, which is the usual shape of the choice when a flotation code and its metric neighbours are set side by side.
Related
- 275/70R18 vs 33x12.50R18
- 275/70R1833.16 in tall
- 265/70R1832.61 in tall
- 285/65R1832.59 in tall
Class: Flotation (imperial). Every figure above is computed from the size code, not stored — see how these numbers are calculated.