Tire Ruler235/65R18 dimensions
| Overall diameter (height) | 30.03″ · 763 mm |
| Section width | 9.25″ · 235 mm |
| Sidewall height | 6.01″ · 153 mm |
| Wheel diameter | 18″ |
| Rim width (rule of thumb) | 6.5–8″ |
| Circumference | 94.3″ |
| Revolutions per mile | 672 |
| In inches (flotation style) | 30.0 × 9.3R18 |
How it’s calculated: the sidewall is 65% of the 235 mm width = 152.8 mm (6.01″). Add two sidewalls to the 18″ wheel: 18 + 2 × 6.01 = 30.03″.
Bigger tires than 235/65R18 on 18″ wheels
| Size | Height | Taller by | 60 mph reads |
|---|---|---|---|
| 265/60R18 | 30.5″ | +0.49″ (+1.6%) | 61.0 mph |
| 245/65R18 | 30.5″ | +0.51″ (+1.7%) | 61.0 mph |
| 275/60R18 | 31.0″ | +0.96″ (+3.2%) | 61.9 mph |
| 255/65R18 | 31.1″ | +1.02″ (+3.4%) | 62.0 mph |
| 265/65R18 | 31.6″ | +1.54″ (+5.1%) | 63.1 mph |
“60 mph reads” is your real speed when a speedometer set up for 235/65R18 shows 60. Above about 3% taller, most trucks need a leveling kit or lift, and the speedometer should be recalibrated.
Same height on a different wheel size
Changing wheel size (plus or minus sizing) while keeping the overall height keeps your speedometer right:
- 30x9.50R15: 30.0″ tall on a 15″ wheel (−0.1%)
- 245/75R16: 30.5″ tall on a 16″ wheel (+1.5%)
- 235/75R16: 29.9″ tall on a 16″ wheel (−0.5%)
- 255/70R16: 30.1″ tall on a 16″ wheel (+0.1%)
- 215/85R16: 30.4″ tall on a 16″ wheel (+1.2%)
- 255/65R17: 30.1″ tall on a 17″ wheel (+0.1%)
- 235/70R17: 30.0″ tall on a 17″ wheel (−0.2%)
- 255/55R19: 30.0″ tall on a 19″ wheel (+0.1%)
- 245/55R19: 29.6″ tall on a 19″ wheel (−1.4%)
- 265/50R20: 30.4″ tall on a 20″ wheel (+1.4%)
- 255/50R20: 30.0″ tall on a 20″ wheel (+0.0%)
- 245/50R20: 29.6″ tall on a 20″ wheel (−1.3%)
- 275/45R20: 29.7″ tall on a 20″ wheel (−0.9%)
- 265/45R21: 30.4″ tall on a 21″ wheel (+1.2%)
- 265/40R22: 30.3″ tall on a 22″ wheel (+1.1%)
Popular 235/65R18 comparisons
Frequently asked questions
Is 235/65R18 a 30 inch tire?
Yes. 235/65R18 is 30.03 inches tall, so it's sold and talked about as a 30-inch tire.
What size is 235/65R18 in inches?
235/65R18 is 30.0 inches tall (overall diameter), 9.3 inches wide, with a 6.0 inch sidewall, and fits an 18 inch wheel.
What tire size is equivalent to 235/65R18?
No common size on an 18" wheel is within 1.5% of 235/65R18's diameter. Use the calculator above to compare any size.
What rim width fits 235/65R18?
As a rule of thumb, about 6.5–8 inches. The tire maker's spec sheet lists the approved range for each model.
How many revolutions per mile does 235/65R18 make?
About 672 revolutions per mile in theory (circumference 94.3 in). Real tires turn slightly more because they flatten under load.