235/45 R18
What size is 235/45 R18?
235/45 R18 has an overall diameter of about 26.33 in, a section width of 9.25 in and a sidewall height of 4.16 in. It turns roughly 766 times per mile. Below are the exact figures plus in-tolerance plus/minus sizes you can switch to safely.
- Overall diameter: 26.33 in.
- Section width: 9.25 in.
- Sidewall height: 4.16 in.
- Revolutions: 476 /km · 766 /mi.
- In-tolerance sizes: 215/55 R17 (-0.1%).
Fitment verdict
215/55 R17 stays within the configured tolerance for 235/45 R18: -0.1% diameter and -0.1% speedometer effect.
| Metric | This size: 235/45 R18 | Alternative: 215/55 R17 | Difference | Verdict |
|---|---|---|---|---|
| Overall diameter | 26.33 in | 26.31 in | -0.1% | Within tolerance |
| Section width | 9.25 in | 8.46 in | -0.79 in | Computed difference |
| Sidewall height | 4.16 in | 4.66 in | +0.49 in | Computed difference |
| Circumference | 82.71 in | 82.66 in | -0.1% | Within tolerance |
| Speedo | 0.0% | -0.1% | -0.1% | Within tolerance |
Seasonal check
Planning a long summer drive?
Use the budget and running-cost tools before a trip, especially if the current tyres are worn or the replacement size changes diameter.
Specification
| Overall diameter | 26.33 in |
|---|---|
| Section width | 9.25 in |
| Sidewall height | 4.16 in |
| Circumference | 82.71 in |
| Revolutions | 476 /km · 766 /mi |
In-tolerance sizes
Alternative sizes that stay within the safe diameter tolerance:
| Size | Diameter | Speedo | Verdict |
|---|---|---|---|
| 215/55 R17 | -0.1% | -0.1% | ✓ OK |
| 205/70 R15 | -0.1% | -0.1% | ✓ OK |
| 215/60 R16 | -0.6% | -0.6% | ✓ OK |
| 255/35 R19 | -1.1% | -1.1% | ✓ OK |
| 225/60 R16 | +1.2% | +1.2% | ✓ OK |
| 225/45 R18 | -1.3% | -1.3% | ✓ OK |
| 245/45 R18 | +1.3% | +1.3% | ✓ OK |
| 245/40 R19 | +1.5% | +1.5% | ✓ OK |
| 225/55 R17 | +1.6% | +1.6% | ✓ OK |
| 245/35 R20 | +1.6% | +1.6% | ✓ OK |
| 205/55 R17 | -1.7% | -1.7% | ✓ OK |
| 225/50 R17 | -1.8% | -1.8% | ✓ OK |
Compare sizes
- Within tolerance · Diameter -0.1%.
- Speedo @ 60: 60 mph → 60.0 mph.
- Sidewall +0.49 in · Width -0.79 in.
How this result is calculated
Computed from nominal tire-size geometry: diameter, circumference and speedometer error. It does not check wheel-arch, suspension or brake clearance.
Methodology- Diameter
- 26.33 in 26.31 in-0.02 in
- Sidewall
- 4.16 in 4.66 in+0.49 in
- Width
- 9.25 in 8.46 in-0.79 in
- Circumference
- 82.71 in 82.66 in-0.1%
- Revs / mile
- 766 767
- Speedo @ 60
- 60 mph 60.0 mph-0.1%
- Current —
235/45 R18 - New —
215/55 R17 - Grounded to the road: the axle rises -0.01 in.
Result report
235/45 R18 215/55 R17 · Within tolerance
Use this size when shopping: 215/55 R17
Geometric estimate. Always verify physical clearance (arches, suspension, brakes) before fitting.
Safe alternative sizes
| Size | Diameter | Speedo @ 100 | Use this |
|---|---|---|---|
−1″ 215/55R17 | -0.1% | -0.1% | |
OE 235/45R18 | +0.0% | +0.0% | |
+1″ 155/60R19 | -0.0% | -0.0% | |
+2″ 145/55R20 | -0.2% | -0.2% |
More tools
- How to read a tire size
- Plus sizing guide
- Speedometer error guide
- 235mm Section width guide
- /45 Aspect ratio guide
- Rim diameter 18"
- Load index chart
- Speed rating chart
- Rim width and tyre fitment guide
- Wheel offset guide
- Wheel spacers guide
- Tyre pressure for heavy loads and towing
What changed
- Reviewed deterministic geometry, load/speed references, sitemap inclusion and localized page shell.