235/75R15 vs 255/75R15: full comparison
| Measurement | 235/75R15 | 255/75R15 | Difference |
|---|---|---|---|
| Diameter | 28.88 in | 30.06 in | +1.18 in+4.1% |
| Section width | 9.25 in | 10.04 in | +0.79 in+8.5% |
| Sidewall height | 6.94 in | 7.53 in | +0.59 in+8.5% |
| Circumference | 90.72 in | 94.43 in | +3.71 in+4.1% |
| Revs per mile | 698 | 671 | −27−3.9% |
Speedometer: indicated vs actual speed
With 255/75R15 fitted where 235/75R15 was the stock/calibrated size:
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 20.8 mph | +0.8 mph |
| 30 mph | 31.2 mph | +1.2 mph |
| 40 mph | 41.6 mph | +1.6 mph |
| 50 mph | 52.0 mph | +2.0 mph |
| 55 mph | 57.2 mph | +2.2 mph |
| 60 mph | 62.5 mph | +2.5 mph |
| 65 mph | 67.7 mph | +2.7 mph |
| 70 mph | 72.9 mph | +2.9 mph |
| 75 mph | 78.1 mph | +3.1 mph |
| 80 mph | 83.3 mph | +3.3 mph |
Recalculate for a gear ratio change too →
Will 255/75R15 fit where 235/75R15 was?
At +4.1%, 255/75R15 is enough larger than 235/75R15 that it commonly needs some accommodation -- trimming plastic liners/fender edges, a spacer, or a leveling kit on trucks/SUVs going bigger. Check clearance at full steering lock and full suspension compression before buying.
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- Speedometer calculator: true speed after a tire or gear ratio change.
Frequently asked questions
How much bigger is 255/75R15 than 235/75R15?
255/75R15 is 1.18 in taller in overall diameter (+4.1%) and 0.79 in wider in section width (+8.5%) than 235/75R15.
Will 255/75R15 fit in place of 235/75R15?
At +4.1%, 255/75R15 is enough larger than 235/75R15 that it commonly needs some accommodation -- trimming plastic liners/fender edges, a spacer, or a leveling kit on trucks/SUVs going bigger. Check clearance at full steering lock and full suspension compression before buying.
Does swapping to 255/75R15 affect my speedometer?
With 255/75R15 fitted where 235/75R15 was calibrated, an indicated 60 mph is really about 62.5 mph. Beyond the ±3% guideline, plan to recalibrate the speedometer/odometer (with a programmer or at the dealer) for an accurate reading.
Does 255/75R15 change the ride height?
Yes -- half the diameter difference shows up at the axle, so 255/75R15 changes ride height by about 0.59 in higher compared with 235/75R15.
Do 235/75R15 and 255/75R15 use the same wheel (rim) diameter?
Yes -- both fit a 15 inch wheel, so only the tire itself changes, not the wheel.