255/70R18 vs 275/65R18: full comparison
| Measurement | 255/70R18 | 275/65R18 | Difference |
|---|---|---|---|
| Diameter | 32.06 in | 32.07 in | +0.02 in+0.1% |
| Section width | 10.04 in | 10.83 in | +0.79 in+7.8% |
| Sidewall height | 7.03 in | 7.04 in | +0.01 in+0.1% |
| Circumference | 100.70 in | 100.77 in | +0.06 in+0.1% |
| Revs per mile | 629 | 629 | 0−0.1% |
Speedometer: indicated vs actual speed
With 275/65R18 fitted where 255/70R18 was the stock/calibrated size:
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 20.0 mph | 0.0 mph |
| 30 mph | 30.0 mph | 0.0 mph |
| 40 mph | 40.0 mph | 0.0 mph |
| 50 mph | 50.0 mph | 0.0 mph |
| 55 mph | 55.0 mph | 0.0 mph |
| 60 mph | 60.0 mph | 0.0 mph |
| 65 mph | 65.0 mph | 0.0 mph |
| 70 mph | 70.0 mph | 0.0 mph |
| 75 mph | 75.0 mph | 0.0 mph |
| 80 mph | 80.0 mph | 0.0 mph |
Recalculate for a gear ratio change too →
Will 275/65R18 fit where 255/70R18 was?
255/70R18 and 275/65R18 are essentially the same overall height (+0.1%), so this is usually a straightforward swap as far as fitment goes -- the main thing to check is wheel width and offset, not diameter.
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- Speedometer calculator: true speed after a tire or gear ratio change.
Frequently asked questions
How much bigger is 275/65R18 than 255/70R18?
275/65R18 is 0.02 in taller in overall diameter (+0.1%) and 0.79 in wider in section width (+7.8%) than 255/70R18.
Will 275/65R18 fit in place of 255/70R18?
255/70R18 and 275/65R18 are essentially the same overall height (+0.1%), so this is usually a straightforward swap as far as fitment goes -- the main thing to check is wheel width and offset, not diameter.
Does swapping to 275/65R18 affect my speedometer?
Since the two sizes are almost the same height, your speedometer will read essentially correctly either way. That small a difference is within the ±3% most shops treat as close enough not to recalibrate.
Does 275/65R18 change the ride height?
Yes -- half the diameter difference shows up at the axle, so 275/65R18 changes ride height by about 0.01 in higher compared with 255/70R18.
Do 255/70R18 and 275/65R18 use the same wheel (rim) diameter?
Yes -- both fit a 18 inch wheel, so only the tire itself changes, not the wheel.