Tire size
275/70R18 in inches — size, and what trucks run it
About 33.2" tall and 10.8" wide — a 33-inch tire in everyday terms. 4 pickup models came on it from the factory.
| Part of the size | Value | What it means |
|---|---|---|
| 275 | 275 mm · 10.8" | Section width — the widest point of the tire, measured sidewall to sidewall, not the tread width. |
| 70 | 7.6" sidewall | Aspect ratio — the sidewall is 70% of the section width. A lower number means a shorter, stiffer sidewall. |
| R | Radial | Construction type. Effectively every modern truck tire is radial. |
| 18 | 18" wheel | Wheel diameter in inches. The tire only fits a wheel of exactly this diameter. |
| Overall | 33.2" | Wheel diameter plus two sidewalls — the number that governs clearance, speedometer accuracy and effective gearing. |
Trucks that came on 275/70R18
Factory fitments on record. Handy in both directions — identifying a set of takeoffs, and finding a donor truck when you want a used set in this size.
Sizes you can swap 275/70R18 for
Same wheel diameter, within 3 per cent of the same overall height — the band that keeps the speedometer, odometer and ABS inside their normal tolerance. Sizes marked factory are ones some pickup was actually sold on, which usually means better availability and a wider choice of tread patterns.
| Size | Overall diameter | Difference | Section width | Availability |
|---|---|---|---|---|
| 295/65R18 | 33.1" | −0.2% | 295 mm | Aftermarket |
| 225/85R18 | 33.1" | −0.3% | 225 mm | Aftermarket |
| 255/75R18 | 33.1" | −0.3% | 255 mm | Aftermarket |
| 245/80R18 | 33.4" | +0.8% | 245 mm | Aftermarket |
| 315/60R18 | 32.9" | −0.8% | 315 mm | Aftermarket |
| 235/80R18 | 32.8" | −1.1% | 235 mm | Aftermarket |
| 305/65R18 | 33.6" | +1.4% | 305 mm | Aftermarket |
| 265/75R18 | 33.6" | +1.5% | 265 mm | Aftermarket |
| 265/70R18 | 32.6" | −1.7% | 265 mm | Factory size on a pickup |
| 285/70R18 | 33.7" | +1.7% | 285 mm | Aftermarket |
| 285/65R18 | 32.6" | −1.7% | 285 mm | Aftermarket |
| 235/85R18 | 33.7" | +1.7% | 235 mm | Aftermarket |
Diameter is only half of fitment. A wider tire needs a wheel wide enough to mount it and enough room at the fender liner and the suspension at full steering lock — which is decided by wheel offset, not by the tire size on the box. And the replacement has to carry at least the load index your door-jamb placard calls for.
275/70R18 — frequently asked
How tall is a 275/70R18 tire?
About 33.2 inches overall — which is why it is usually talked about as a 33-inch tire. That comes from the wheel diameter of 18 inches plus two sidewalls of 7.6 inches each. The sidewall height is 70 per cent of the 275 mm section width, not of the wheel.
What does 275/70R18 mean?
275 is the section width in millimetres, measured at the widest point of the tire rather than across the tread. 70 is the aspect ratio: the sidewall is 70 per cent of that width. The R means radial construction. 18 is the wheel diameter in inches. Put together, the tire is about 10.8 inches wide and 33.2 inches tall.
What trucks use 275/70R18?
On record, 4 pickup models came on 275/70R18 from the factory: Ford F-250 Super Duty (2005–2026), Ford F-350 Super Duty (2005–2026), Ram 2500 (2003–2026), Ram 3500 (2003–2026). That makes it a common takeoff size, so used sets are usually easy to find.
What can I replace 275/70R18 with?
The safe substitutes are the sizes within about 3 per cent of the same overall diameter, because that keeps the speedometer, odometer and ABS inside their normal tolerance. On the same wheel diameter that means 295/65R18, 225/85R18, 255/75R18, 245/80R18, 315/60R18, all listed with their exact difference further down this page. Going outside 3 per cent usually means recalibrating.
How many revolutions per mile does a 275/70R18 turn?
Roughly 608 revolutions per mile, from a rolling circumference of about 104.2 inches. That figure is what the speedometer and odometer are calibrated against — a tire that turns fewer revolutions per mile than stock makes the speedometer read low.
Is 275/70R18 a 33-inch tire?
Effectively yes. It works out to 33.2 inches, so it is sold and discussed as a 33. Flotation sizes such as 33x12.50R18 state the diameter directly instead. When you compare across the two systems, convert both to overall diameter in inches rather than trusting the name on the box.
