245/35R20vs285/30R20
Proportional side-by-side visual comparison, dimensional specs, speedometer calibration, and fitment guide.
Comparison Summary & Verdict
Comparing 245/35R20 (baseline) to 285/30R20 (target):The 285/30R20 is 0.02" shorter in overall diameter (-0.07%) and 1.57" wider.
Side-by-Side Dimension Specifications
Full dimensional metrics calculated according to ISO standardized tire formulas.
| Specification | 245/35R20 (Stock) | 285/30R20 (Target) | Difference (Delta) |
|---|---|---|---|
| Overall Diameter | 26.75" (679 mm) | 26.73" (679 mm) | -0.02" (-0.07%) |
| Section Width | 9.65" (245 mm) | 11.22" (285 mm) | +1.57" (+40 mm) |
| Sidewall Height | 3.38" (86 mm) | 3.37" (86 mm) | -0.01" |
| Circumference | 84.04" (2135 mm) | 83.98" (2133 mm) | -0.06" |
| Revolutions per Mile | 777 revs/mi | 778 revs/mi | +1 revs/mi |
| Wheel Rim Diameter | 20" | 20" | Same wheel diameter (Direct fit) |
| Recommended Rim Width | 6.6" – 8.6" | 7.7" – 10.0" | n/a |
Speedometer & Odometer Calibration Table
Because vehicle speedometers measure axle rotation, changing tire circumference alters speed readings. When switching from 245/35R20 to 285/30R20:
| Actual Speed (GPS) | Speedometer Reading on 285/30R20 | Variance / Error |
|---|---|---|
| 20 mph | 20.0 mph | +0.0 mph |
| 30 mph | 30.0 mph | +0.0 mph |
| 45 mph | 45.0 mph | +0.0 mph |
| 60 mph | 60.0 mph | +0.0 mph |
| 70 mph | 70.1 mph | +0.1 mph |
| 80 mph | 80.1 mph | +0.1 mph |
Fitment & Practical Considerations
Clearance & Rubbing
Because 285/30R20 is significantly different in size (-0.02" shorter), check clearance with suspension components, brake calipers, and wheel wells at full steering lock and full compression.
Gearing & Acceleration
Gearing and acceleration changes will be negligible between these two sizes.
Wheel & Rim Width
Both sizes use a standard 20" wheel rim. Ensure your existing rim width falls within 7.7" to 10.0" for optimal tire bead seating.
Official Calculation Standards & References
All dimension formulas, revs/mile conversions, rim width brackets, and speedometer error deltas on Tire Visualizer are calculated strictly according to international automotive engineering standards:
ISO 4000-1 metric tire dimensional standards, section width ratios, and approved measuring rim definitions.
North American standards for overall tire diameter, static loaded radius, and revolutions-per-mile benchmarks.
Federal motor vehicle safety standards governing pneumatic tire sizing, load indices, and speedometer tolerance limits.
Engineering standards (SAE J2047 & J1982) for dynamic tire rolling radius and speedometer calibration accuracy.
Frequently Asked Questions: 245/35R20 vs 285/30R20
Can I replace 245/35R20 with 285/30R20?
Yes. The diameter difference between 245/35R20 and 285/30R20 is -0.07%, which is within the industry standard ±3% safety margin. It is generally a safe direct replacement without requiring speedometer recalibration or suspension modifications.
How does 285/30R20 affect my speedometer compared to 245/35R20?
When driving at an actual speed of 60 mph on 285/30R20, your speedometer will read 60 mph (a difference of 0.0 mph). Your vehicle will be traveling slightly slower than indicated.
Will 285/30R20 change my vehicle's ride height?
285/30R20 has an overall diameter of 26.73" compared to 26.75" on 245/35R20. This will change your ground clearance by -0.01 inches (lower).
What wheel rim width is needed for 285/30R20?
For 285/30R20, the recommended wheel rim width range is typically 7.7" to 10.0" wide, mounted on a 20" diameter wheel.
Compare Other Tire Sizes
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