235/40R18 tire size
A 235/40R18 tire is 235 mm wide with a 94.0 mm sidewall, 40% of the width, on a 18-inch rim, which puts the whole tire at 645.2 mm, or about 25.4 inches, tall. Our data lists 1 models fitted with it from the factory, mostly sedans.
Overall height
645.2 mm
25.4 in
Sidewall
94.0 mm
40%
Circumference
2,027 mm
Revs per km
493
Actual dimensions of 235/40R18
| Section width | 235 mm (9.3 in) |
| Sidewall height | 94.0 mm (3.70 in) |
| Rim diameter | 18 in (457.2 mm) |
| Overall diameter | 645.2 mm (25.4 in) |
| Circumference | 2,027 mm |
| Revolutions per km | 493 |
| Inch notation (height x width) | 25.4x9.3R18 |
Worked out: sidewall 235 x 0.4 = 94 mm, rim 18 x 25.4 = 457.2 mm, overall 457.2 + (94 x 2) = 645.2 mm, circumference 3.1416 x 645.2 = 2,027 mm. One turn of the tire moves the car about 2.03 m, which is 493 turns per kilometer. New to sidewall codes? See how to read a tire size.
These are nominal figures from the standard formula. Real tires vary slightly by brand and squat a little under the weight of the car.
Cars fitted with 235/40R18 from the factory
Models whose Thai-market specification lists 235/40R18; the source column links to the spec we checked.
| Model | Years | Grades | Source |
|---|---|---|---|
| Honda Civic (FE) | 2021–present | RS | honda.co.th |
Cars that can switch to 235/40R18
These cars leave the factory on another size within 3% of the height of 235/40R18. Whether it fits still depends on rim width and wheel-well clearance.
| Model | Factory size | Height difference | Wheel |
|---|---|---|---|
| Mazda32019–present | 215/45R18 | −0.85% | Same wheel |
| Honda Civic (FC)2016–2021 | 215/50R17 | −0.25% | Needs 18-inch wheels |
| MG4 Electric2022–present | 215/50R17 | −0.25% | Needs 18-inch wheels |
| MG5Current model | 215/50R17 | −0.25% | Needs 18-inch wheels |
| MG ZSCurrent model | 215/55R16 | +0.36% | Needs 18-inch wheels |
| Toyota Veloz2022–present | 205/50R17 | +1.32% | Needs 18-inch wheels |
| Toyota Yaris ATIV HEV2025–present | 205/50R17 | +1.32% | Needs 18-inch wheels |
| BYD Dolphin2023–present | 205/50R17 | +1.32% | Needs 18-inch wheels |
| Toyota Corolla Altis2019–present | 225/45R17 | +1.72% | Needs 18-inch wheels |
| Honda Accord e:HEV2024–present | 225/50R17 | −1.77% | Needs 18-inch wheels |
| Mitsubishi Xpander Cross HEV2024–present | 205/55R17 | −1.84% | Needs 18-inch wheels |
| Nissan Kicks e-POWERCurrent model | 205/55R17 | −1.84% | Needs 18-inch wheels |
Showing the 12 closest of 15 models.
Sizes that can replace 235/40R18
Sizes within ±3% of the overall height of 235/40R18. “At 100 km/h” is the real speed when the speedometer reads 100.
| Size | Height | Difference | At 100 km/h | Sidewall | Match | Compare |
|---|---|---|---|---|---|---|
| 215/50R17 | 646.8 mm | +1.6 mm (+0.25%) | 100.2 km/h | 107.5 mm | Very close | Compare |
| 235/35R19 | 647.1 mm | +1.9 mm (+0.29%) | 100.3 km/h | 82.3 mm | Very close | Compare |
| 235/45R17 | 643.3 mm | −1.9 mm (−0.29%) | 99.7 km/h | 105.8 mm | Very close | Compare |
| 215/45R18 | 650.7 mm | +5.5 mm (+0.85%) | 100.9 km/h | 96.8 mm | Close | Compare |
| 245/45R17 | 652.3 mm | +7.1 mm (+1.10%) | 101.1 km/h | 110.3 mm | Close | Compare |
| 225/40R18 | 637.2 mm | −8.0 mm (−1.24%) | 98.8 km/h | 90.0 mm | Close | Compare |
| 245/40R18 | 653.2 mm | +8.0 mm (+1.24%) | 101.2 km/h | 98.0 mm | Close | Compare |
| 205/50R17 | 636.8 mm | −8.4 mm (−1.30%) | 98.7 km/h | 102.5 mm | Close | Compare |
- Keeping your wheels, the closest is 215/45R18 at 650.7 mm, +5.5 mm (+0.85%) from the original. With the speedometer on 100 km/h, the car would actually be doing about 100.9 km/h. Ground clearance rises by about 2.8 mm.
- Moving up to 19-inch wheels, the closest height match is 235/35R19 (+0.29%), with the sidewall dropping from 94.0 mm to 82.3 mm.
- Going down to 17-inch wheels, 215/50R17 (+0.25%) is the closest match and raises the sidewall to 107.5 mm.
- A larger or wider tire also changes acceleration, fuel use and steering weight, so look beyond the percentage.
Buying 235/40R18 tires
Low-profile sizes are mostly performance tires and price rises with W or Y speed ratings; comfort-focused models exist in the same size if you do not drive hard.
Check the production date in the DOT code before paying.
Check current prices
Search by brand
Links open marketplace search results; prices change constantly and not every brand makes this size.
Load index and speed rating for 235/40R18
The code after the size on the sidewall, as in 235/40R18 91V, is the load index and speed symbol. The common ratings for this size:
| Version | Index | Per tire | Four tires |
|---|---|---|---|
| Standard load (SL) | 91 | 615 kg | 2,460 kg |
| Extra load (XL) | 95 | 690 kg | 2,760 kg |
The new tire's load index and speed symbol must be no lower than the door placard, and it only carries its rated load at the correct pressure.
Common speed symbols in this size
V
240 km/h
W
270 km/h
Y
300 km/h
235/40R18 questions
How tall is a 235/40R18 tire?
About 25.4 inches, or 645.2 mm, from top to bottom before it carries weight. Each sidewall is 94.0 mm tall and the tire is 235 mm (9.3 in) wide.
Which cars use 235/40R18 tires?
From Thai-market specifications, 235/40R18 comes on Honda Civic (FE).
Can I fit 215/45R18 instead of 235/40R18?
Size-wise, yes: the height differs by +0.85% (+5.5 mm), so an indicated 100 km/h is really about 100.9 km/h. The tread is 20 mm narrower. Check rim width and load index first.
How much weight can a 235/40R18 tire carry?
Most standard-load versions carry load index 91: 615 kg per tire, 2,460 kg across four. XL versions are rated 95, or 690 kg per tire. Look for the number after the size on the sidewall, as in 235/40R18 91V.
Other 18-inch sizes
To compare other sizes yourself, use the tire size calculator; changing rim size, try plus/minus sizing; and see speedometer error by speed.