Tire RulerType any tire size to see it in inches, or compare two sizes side by side, drawn to scale.
Type it as it appears on the sidewall: 275/60R20, LT265/70R17 or 33x12.50R20.
| 265/70R17 | 285/70R17 | Difference | |
|---|---|---|---|
| Overall diameter | 31.6″ 803 mm | 32.7″ 831 mm | +1.10″ (+3.5%) |
| Section width | 10.4″ 265 mm | 11.2″ 285 mm | +0.79″ |
| Sidewall height | 7.30″ 186 mm | 7.85″ 200 mm | +0.55″ |
| Wheel (rim) diameter | 17″ | 17″ | same |
| Circumference | 99.3″ 2522 mm | 102.8″ 2610 mm | +3.5″ |
| Revolutions per mile | 638 | 617 | −22 |
| Ground clearance | +0.55″ |
285/70R17 is 1.10″ taller (3.5%) and 0.79″ wider than 265/70R17. With a speedometer set up for 265/70R17, an indicated 60 mph is really 62.1 mph on 285/70R17, so the gauge reads 3.5% low. Ground clearance at the axle changes by +0.55″.
A 3.5% difference is more than the ±3% shops commonly use as a limit: plan to recalibrate the speedometer, check clearance (and lift or leveling needs), and consider regearing if it's a big jump.
| Speedometer shows | Real speed on 285/70R17 |
|---|---|
| 30 mph | 31.0 mph |
| 45 mph | 46.6 mph |
| 60 mph | 62.1 mph |
| 70 mph | 72.4 mph |
| 80 mph | 82.8 mph |
Any tire size in inches, or two sizes side by side, drawn to scale.
Open →Your real speed after a tire size change.
Open →Regear for bigger tires, effective ratio and engine RPM.
Open →Every common size in inches, grouped by wheel size.
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