275/65R18 vs 285/65R18: Tire Size Comparison
285/65R18 is 0.51 inches taller than 275/65R18 (32.59″ vs 32.07″, +1.6%) and 0.39 inches wider. The difference is within the common ±3% guideline. At an indicated 60 mph you would be doing 61 mph.
| 275/65R18 | 285/65R18 | Difference | |
|---|---|---|---|
| Overall diameter | 32.07 in | 32.59 in | +0.51 |
| Section width | 10.83 in | 11.22 in | +0.39 |
| Sidewall height | 7.04 in | 7.29 in | +0.26 |
| Circumference | 100.8 in | 102.4 in | +1.61 |
| Revolutions per mile | 629 | 619 | −10 |
275/65R18 vs 285/65R18 dimensions
| 275/65R18 | 285/65R18 | Difference | |
|---|---|---|---|
| Overall diameter | 32.07 in (815 mm) | 32.59 in (828 mm) | +0.51 in (+1.6%) |
| Section width | 10.83 in | 11.22 in | +0.39 in |
| Sidewall height | 7.04 in | 7.29 in | +0.26 in |
| Wheel diameter | 18 in | 18 in | same wheel |
| Circumference | 100.8 in | 102.4 in | +1.61 in |
| Revolutions per mile | 629 | 619 | -10 |
Nominal dimensions calculated from the size code. Real tires vary slightly by brand, tread depth and inflation.
Speedometer difference with 285/65R18
| Speedometer shows | Actual speed on 285/65R18 | Difference |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 mph |
| 45 mph | 45.7 mph | +0.7 mph |
| 60 mph | 61 mph | +1 mph |
| 70 mph | 71.1 mph | +1.1 mph |
| 80 mph | 81.3 mph | +1.3 mph |
Assumes your speedometer is accurate on 275/65R18. Because 285/65R18 is taller, you travel slightly faster than indicated and the odometer under-counts: 10,000 miles on the odometer is about 10,160 real miles.
What changes if you switch
- Ride height: up about 0.26 in (half the diameter change).
- Wheels: both fit a 18-inch wheel; check the tire's approved rim width range.
- Sidewall: a taller sidewall usually rides softer and resists pothole damage, with a little less steering sharpness.
- Effective gearing: slightly taller, so marginally lower engine rpm at speed and slightly slower acceleration.
- Match the original load index and speed rating or higher, and check for rubbing at full steering lock and full suspension compression.
Related tire size comparisons
Frequently asked questions
Can I use 285/65R18 instead of 275/65R18?
285/65R18 is +1.6% in overall diameter compared with 275/65R18 (32.59″ vs 32.07″). That is inside the common ±3% guideline, so it is often used as an alternative. Check your vehicle placard, load index, speed rating and clearance before switching.
How much taller is 285/65R18 than 275/65R18?
285/65R18 is 0.51 inches taller overall, which raises ride height by about 0.26 inches. Sidewall height changes from 7.04″ to 7.29″.
How much wider is 285/65R18 than 275/65R18?
Section width goes from 10.83″ (275 mm) to 11.22″ (285 mm), a difference of +0.39 in. Actual width also depends on the rim width it is mounted on.
How does 285/65R18 affect my speedometer?
With 285/65R18 fitted in place of 275/65R18, when the speedometer shows 60 mph you are actually going about 61 mph. The odometer will record 10,000 miles when you have driven about 10,160.