275/70R17 vs 275/65R18 Side-by-side tire size comparison with specs and compatibility
Compatibility
-0.26% diameter difference
✓ Safe Swap
This tire swap is within the safe 3% diameter threshold. It should not cause issues with speedometer accuracy, ABS, or traction control systems.
Full Specifications Comparison
| Specification | 275/70R17 | 275/65R18 | Difference |
|---|---|---|---|
| Overall Diameter | 816.8 mm (32.2") | 814.7 mm (32.1") | -2.1 mm |
| Section Width | 275 mm (10.8") | 275 mm (10.8") | 0 mm |
| Sidewall Height | 192.5 mm | 178.8 mm | -13.7 mm |
| Circumference | 2566.1 mm | 2559.5 mm | -6.6 mm |
| Revolutions/Mile | 627 | 629 | +2 |
| Aspect Ratio | 70% | 65% | -5% |
| Rim Diameter | 17" | 18" | +1" |
Key Impact Summary
Ground Clearance
-1 mm
Speedometer Error
-0.26%
Width Change
0 mm
Sidewall Change
-13.7 mm
Speedometer Correction Table
When switching from 275/70R17 to 275/65R18, your speedometer will over-read. Here is the correction at common speeds:
| Speedometer Shows | Actual Speed (mph) | Difference |
|---|---|---|
| 30 mph | 29.9 mph | -0.1 mph |
| 40 mph | 39.9 mph | -0.1 mph |
| 50 mph | 49.9 mph | -0.1 mph |
| 60 mph | 59.8 mph | -0.2 mph |
| 70 mph | 69.8 mph | -0.2 mph |
| 80 mph | 79.8 mph | -0.2 mph |
| 90 mph | 89.8 mph | -0.2 mph |
| 100 mph | 99.7 mph | -0.3 mph |
| 110 mph | 109.7 mph | -0.3 mph |
| 120 mph | 119.7 mph | -0.3 mph |
What This Swap Means
Shorter sidewall: The 13.7mm decrease in sidewall height improves steering response and cornering precision. However, ride quality becomes firmer and the wheels are more vulnerable to pothole damage. This is a common trade-off when upsizing wheels (plus-sizing).
Ground clearance: Decreases by 1mm, lowering the center of gravity slightly which can improve handling stability.
Vehicles Using 275/65R18
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Individual Tire Specs
Frequently Asked Questions
Yes, this swap is generally safe. The diameter difference is -0.26% (-2.1mm). This is within the safe 3% threshold and should not significantly affect your speedometer, ABS, or traction control.
Switching from 275/70R17 to 275/65R18 creates a -0.26% speedometer error. Your actual speed will be slower than displayed — at an indicated 60 mph, you'll actually be going 59.8 mph.
Switching from 275/70R17 to 275/65R18 changes ground clearance by -1mm. The vehicle will sit 1mm lower. Ground clearance change equals half the overall diameter difference.