275/65R18 vs 275/70R18
275/70R18 is 1.08 in (3.38%) taller than 275/65R18. Edit either size below to try other combinations.
Metric (265/70R17) or inch (33x12.50R20). Axle ratio is used for the RPM table only.
275/70R18 is 1.08 in (28 mm) taller than 275/65R18 (+3.4%). With a speedometer calibrated for 275/65R18, an indicated 60 mph is really 62.0 mph. The diameter difference is more than ±3%, a range often quoted as a rule of thumb, so speedometer, gearing and clearance effects are larger.
Geometry only: this does not confirm that a size fits, is approved for or is safe on a particular vehicle. Wheel width and offset, suspension, clearances, load index, speed rating, the vehicle maker's specification and local regulations all apply — check with your owner's manual and a qualified tire professional.
| 275/65R18 | 275/70R18 | Difference | |
|---|---|---|---|
| Diameter | 32.07 in | 33.16 in | +1.08 in (+3.38%) |
| Diameter (mm) | 815 mm | 842 mm | +28 mm |
| Width | 10.83 in | 10.83 in | ±0.00 in (±0 mm) |
| Sidewall | 7.04 in | 7.58 in | +0.54 in |
| Rim | 18 in | 18 in | ±0.0 in |
| Circumference | 100.8 in | 104.2 in | +3.40 in |
| Revs per mile | 629 | 608 | −21 |
| Ground clearance change | — | — | +0.54 in |
Speedometer error
| Speedometer shows | True speed on 275/70R18 | Difference |
|---|---|---|
| 20 mph | 20.7 mph | +0.7 mph |
| 30 mph | 31.0 mph | +1.0 mph |
| 40 mph | 41.4 mph | +1.4 mph |
| 50 mph | 51.7 mph | +1.7 mph |
| 60 mph | 62.0 mph | +2.0 mph |
| 70 mph | 72.4 mph | +2.4 mph |
| 80 mph | 82.7 mph | +2.7 mph |
| Speedometer shows | True speed on 275/70R18 | Difference |
|---|---|---|
| 30 km/h | 31.0 km/h | +1.0 km/h |
| 50 km/h | 51.7 km/h | +1.7 km/h |
| 80 km/h | 82.7 km/h | +2.7 km/h |
| 100 km/h | 103.4 km/h | +3.4 km/h |
| 120 km/h | 124.1 km/h | +4.1 km/h |
Assumes the speedometer was accurate on 275/65R18. Factory speedometers often read slightly high on purpose; check against GPS.
Engine RPM and gearing
| Road speed | 275/65R18 | 275/70R18 | Change |
|---|---|---|---|
| 45 mph | 1,759 rpm | 1,702 rpm | −57 rpm |
| 55 mph | 2,150 rpm | 2,080 rpm | −70 rpm |
| 65 mph | 2,541 rpm | 2,458 rpm | −83 rpm |
| 75 mph | 2,932 rpm | 2,836 rpm | −96 rpm |
To restore the original effective gearing on 275/70R18 you would need an axle ratio of about 3.86 (nearest ratios on our reference list: 3.73 or 3.91). For overdrive gears multiply the RPM by the gear ratio (e.g. ×0.69).
Other 18-inch sizes within ±3% of 275/65R18
| Size | Diameter | Width | vs original |
|---|---|---|---|
| 325/55R18 | 32.07 in | 12.80 in | ±0.00% |
| 255/70R18 | 32.06 in | 10.04 in | −0.06% |
| 355/50R18 | 31.98 in | 13.98 in | −0.31% |
| 225/80R18 | 32.17 in | 8.86 in | +0.31% |
| 295/60R18 | 31.94 in | 11.61 in | −0.43% |
| 235/75R18 | 31.88 in | 9.25 in | −0.61% |
| 215/85R18 | 32.39 in | 8.46 in | +0.98% |
| 305/60R18 | 32.41 in | 12.01 in | +1.04% |
Computed combinations of standard widths and aspect ratios; not every size is manufactured. A similar diameter does not mean a size fits or is approved for your vehicle.
What changes if you switch
- The 3.38% height difference is more than the ±3% often quoted as a rule of thumb; a speedometer calibrated for 275/65R18 reads about 3.3% low, and clearance at full steering lock and suspension travel changes more.
- Both sizes are made for 18-inch wheels. Whether a given wheel's width and offset suit 275/70R18 has to be checked against the tire maker's approved rim widths and the vehicle.
- Ground clearance under the axles increases by about 0.54 in (half the height difference).
- Sidewall height goes from 7.04 in to 7.58 in. Taller sidewalls generally flex more; ride and handling also depend on the tire's construction and pressure.
Size pages
Related comparisons
Frequently asked questions
Is 275/70R18 bigger than 275/65R18?
275/70R18 is 1.08 in (28 mm, 3.38%) taller than 275/65R18.
Can I replace 275/65R18 with 275/70R18?
This page can only compare dimensions: the diameter difference is 3.38%, more than the ±3% often quoted as a rule of thumb. It cannot tell you whether 275/70R18 fits or is approved for your vehicle — that depends on wheel width and offset, suspension and body clearance, the load index and speed rating your vehicle requires, and local regulations. Check your owner's manual and placard and ask a qualified tire professional.
How much does the speedometer change from 275/65R18 to 275/70R18?
It reads low by about 3.27% of the indicated speed: at an indicated 60 mph you are actually doing 62.0 mph (at 100 km/h, 103.4 km/h).
How does 275/70R18 change engine RPM?
Example with a 3.73 axle ratio in direct drive at 65 mph: 2541 rpm on 275/65R18 and 2458 rpm on 275/70R18. Restoring the original effective gearing would take an axle ratio of about 3.86. Enter your own axle ratio in the tool above; this is arithmetic, not a recommendation to change gears.
Nominal geometry for planning only; not fitment advice. See methodology.
Related tools
- Speedometer error calculator
How fast you are really going after a tire change.
- Gear ratio & RPM
Engine RPM and the regear needed for bigger tires.
- Plus size calculator
Sizes that keep your diameter on a bigger or smaller wheel.
- Inch ↔ metric converter
33x12.50R17 to metric and back, with closest equivalents.