235/40R18 tire size
A 235/40R18 tire is 25.40 inches (645.2 mm) tall, 9.25 in (235 mm) wide and fits a 18-inch wheel. In inch notation it is roughly a 25.4x9.3R18.
| Overall diameter | 25.40 in | 645.2 mm |
|---|---|---|
| Section width | 9.25 in | 235 mm |
| Sidewall height | 3.70 in | 94.0 mm |
| Circumference | 79.80 in | 2,027 mm |
| Revolutions | 794.0 per mile | 493.4 per km |
| Rim diameter | 18 in | 457.2 mm |
Compare 235/40R18 with another size
Alternative sizes on the same 18-inch wheel
Sizes in use within ±3 % of the overall diameter of 235/40R18:
Plus and minus sizes for 235/40R18
| Size | Wheel | Diameter | Difference |
|---|---|---|---|
| 215/55R16 | Minus 2 (16 in) | 25.31 in | −0.36% |
| 235/50R16 | Minus 2 (16 in) | 25.25 in | −0.59% |
| 245/50R16 | Minus 2 (16 in) | 25.65 in | +0.96% |
| 205/60R16 | Minus 2 (16 in) | 25.69 in | +1.12% |
| 265/40R17 | Minus 1 (17 in) | 25.35 in | −0.22% |
| 215/50R17 | Minus 1 (17 in) | 25.46 in | +0.25% |
| 235/45R17 | Minus 1 (17 in) | 25.33 in | −0.29% |
| 275/40R17 | Minus 1 (17 in) | 25.66 in | +1.02% |
| 235/35R19 | Plus 1 (19 in) | 25.48 in | +0.29% |
| 275/30R19 | Plus 1 (19 in) | 25.50 in | +0.37% |
| 265/30R19 | Plus 1 (19 in) | 25.26 in | −0.56% |
| 225/35R19 | Plus 1 (19 in) | 25.20 in | −0.79% |
| 245/30R20 | Plus 2 (20 in) | 25.79 in | +1.52% |
| 255/30R20 | Plus 2 (20 in) | 26.02 in | +2.45% |
Vehicles approved with 235/40R18 tires
Models whose Swiss type approval lists 235/40R18 as a standard or optional size (2,506 approvals in total). Always check your own vehicle's placard or papers.
- Ford Focus
- Volkswagen Passat
- Mercedes-Benz E-Class
- Ford Mondeo
- Ford Grand C-MAX
- Ford C-MAX
- Volvo S60
- Volvo V60
- Volvo S80
- Volvo V70
- Audi A4
- Honda Civic
- Volkswagen Scirocco
- Mercedes-Benz CLA
- Volkswagen CC
- Renault Megane
- Mercedes-Benz A-Class
- Mercedes-Benz C-Class
- Lotus Exige
- Volkswagen EOS
- Audi A6
- Alpine A110
- BMW 5 Series
- Saab 9-5
- Volvo C70
- BMW M2
- Ktm X-Bow
- Porsche 911
- Aston Martin DB7
- Mercedes-Benz SLC
- Quattro Audi
- Alfa Romeo 166
- Alfa Romeo 4C
- Kia K4
- Audi R8
- Porsche Cayman
- BMW M3
- Lancia Thesis
- Porsche Boxster
- Cadillac ATS
Source: Swiss Federal Roads Office (FEDRO/ASTRA), open government data. Original data (downloaded 2026-09-29). Data processed by us; errors in processing are ours, not the publisher's.
Nearby 18-inch sizes
- 215/35R18 (−5.8%)
- 215/40R18 (−2.5%)
- 215/45R18 (+0.9%)
- 215/50R18 (+4.2%)
- 225/35R18 (−4.7%)
- 225/40R18 (−1.2%)
- 225/45R18 (+2.2%)
- 225/50R18 (+5.7%)
- 235/35R18 (−3.6%)
- 235/45R18 (+3.6%)
- 235/50R18 (+7.3%)
- 245/35R18 (−2.6%)
- 245/40R18 (+1.2%)
- 245/45R18 (+5.0%)
- 245/50R18 (+8.8%)
- 255/35R18 (−1.5%)
- 255/40R18 (+2.5%)
- 255/45R18 (+6.4%)
- 255/50R18 (+10.4%)
Reading the 235/40R18 size
- 235 — section width in millimetres (9.25 in).
- 40 — aspect ratio: the sidewall is 40 % of the width, 94.0 mm.
- R — radial construction (ZR on the sidewall means a high-speed rated radial; the dimensions are the same).
- 18 — fits a 18-inch diameter wheel.
The load index and speed rating (for example 91V) follow the size on the sidewall. They must meet at least the values on your vehicle's tire placard.