235/55 R18
What size is 235/55 R18?
235/55 R18 has an overall diameter of about 28.18 in, a section width of 9.25 in and a sidewall height of 5.09 in. It turns roughly 716 times per mile. Below are the exact figures plus in-tolerance plus/minus sizes you can switch to safely.
- Overall diameter: 28.18 in.
- Section width: 9.25 in.
- Sidewall height: 5.09 in.
- Revolutions: 445 /km · 716 /mi.
- In-tolerance sizes: 235/50 R19 (+0.3%).
Fitment verdict
235/50 R19 stays within the configured tolerance for 235/55 R18: +0.3% diameter and +0.3% speedometer effect.
| Metric | This size: 235/55 R18 | Alternative: 235/50 R19 | Difference | Verdict |
|---|---|---|---|---|
| Overall diameter | 28.18 in | 28.25 in | +0.3% | Within tolerance |
| Section width | 9.25 in | 9.25 in | 0.00 in | Computed difference |
| Sidewall height | 5.09 in | 4.63 in | -0.46 in | Computed difference |
| Circumference | 88.52 in | 88.76 in | +0.3% | Within tolerance |
| Speedo | 0.0% | +0.3% | +0.3% | 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 | 28.18 in |
|---|---|
| Section width | 9.25 in |
| Sidewall height | 5.09 in |
| Circumference | 88.52 in |
| Revolutions | 445 /km · 716 /mi |
In-tolerance sizes
Alternative sizes that stay within the safe diameter tolerance:
| Size | Diameter | Speedo | Verdict |
|---|---|---|---|
| 235/50 R19 | +0.3% | +0.3% | ✓ OK |
| 235/60 R17 | -0.3% | -0.3% | ✓ OK |
| 255/45 R19 | -0.5% | -0.5% | ✓ OK |
| 235/65 R16 | -0.5% | -0.5% | ✓ OK |
| 255/35 R21 | -0.5% | -0.5% | ✓ OK |
| 215/65 R17 | -0.6% | -0.6% | ✓ OK |
| 225/65 R17 | +1.2% | +1.2% | ✓ OK |
| 225/55 R18 | -1.5% | -1.5% | ✓ OK |
| 275/40 R20 | +1.7% | +1.7% | ✓ OK |
| 245/45 R19 | -1.8% | -1.8% | ✓ OK |
| 245/45 R20 | +1.8% | +1.8% | ✓ OK |
| 275/40 R19 | -1.8% | -1.8% | ✓ OK |
Compare sizes
- Within tolerance · Diameter +0.3%.
- Speedo @ 60: 60 mph → 60.2 mph.
- Sidewall -0.46 in · Width +0.00 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
- 28.18 in 28.25 in+0.07 in
- Sidewall
- 5.09 in 4.63 in-0.46 in
- Width
- 9.25 in 9.25 in+0.00 in
- Circumference
- 88.52 in 88.76 in+0.3%
- Revs / mile
- 716 714
- Speedo @ 60
- 60 mph 60.2 mph+0.3%
- Current —
235/55 R18 - New —
235/50 R19 - Grounded to the road: the axle rises +0.04 in.
Result report
235/55 R18 235/50 R19 · Within tolerance
Use this size when shopping: 235/50 R19
Geometric estimate. Always verify physical clearance (arches, suspension, brakes) before fitting.
Safe alternative sizes
| Size | Diameter | Speedo @ 100 | Use this |
|---|---|---|---|
−1″ 355/40R17 | +0.0% | +0.0% | |
OE 235/55R18 | +0.0% | +0.0% | |
+1″ 155/75R19 | -0.1% | -0.1% | |
+2″ 345/30R20 | -0.1% | -0.1% |
More tools
- How to read a tire size
- Plus sizing guide
- Speedometer error guide
- 235mm Section width guide
- /55 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.