255/55R18 tire size
A 255/55R18 tire is 255 mm wide with a 140.3 mm sidewall, 55% of the width, on a 18-inch rim, which puts the whole tire at 737.7 mm, or about 29.0 inches, tall. No model in our data leaves the factory on it, but it can replace the original size on 5 models within 3% of the height.
Overall height
737.7 mm
29.0 in
Sidewall
140.3 mm
55%
Circumference
2,318 mm
Revs per km
431
Actual dimensions of 255/55R18
| Section width | 255 mm (10.0 in) |
| Sidewall height | 140.3 mm (5.52 in) |
| Rim diameter | 18 in (457.2 mm) |
| Overall diameter | 737.7 mm (29.0 in) |
| Circumference | 2,318 mm |
| Revolutions per km | 431 |
| Inch notation (height x width) | 29.0x10.0R18 |
Worked out: sidewall 255 x 0.55 = 140.25 mm, rim 18 x 25.4 = 457.2 mm, overall 457.2 + (140.25 x 2) = 737.7 mm, circumference 3.1416 x 737.7 = 2,318 mm. One turn of the tire moves the car about 2.32 m, which is 431 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 255/55R18 from the factory
No model sold in Thailand in our data leaves the factory on 255/55R18.
Cars that can switch to 255/55R18
These cars leave the factory on another size within 3% of the height of 255/55R18. Whether it fits still depends on rim width and wheel-well clearance.
| Model | Factory size | Height difference | Wheel |
|---|---|---|---|
| Honda CR-V2023–present | 235/60R18 | −0.20% | Same wheel |
| Honda CR-V2017–2022 | 235/60R18 | −0.20% | Same wheel |
| Mazda CX-52017–present | 225/55R19 | +1.04% | Needs 18-inch wheels |
| Mitsubishi Triton2015–2023 | 245/70R16 | −1.56% | Needs 18-inch wheels |
| MG ExtenderCurrent model | 245/70R16 | −1.56% | Needs 18-inch wheels |
Sizes that can replace 255/55R18
Sizes within ±3% of the overall height of 255/55R18. “At 100 km/h” is the real speed when the speedometer reads 100.
| Size | Height | Difference | At 100 km/h | Sidewall | Match | Compare |
|---|---|---|---|---|---|---|
| 255/60R17 | 737.8 mm | +0.1 mm (+0.01%) | 100.0 km/h | 153.0 mm | Very close | Compare |
| 255/50R19 | 737.6 mm | −0.1 mm (−0.01%) | 100.0 km/h | 127.5 mm | Very close | Compare |
| 255/45R20 | 737.5 mm | −0.2 mm (−0.03%) | 100.0 km/h | 114.8 mm | Very close | Compare |
| 235/65R17 | 737.3 mm | −0.4 mm (−0.05%) | 99.9 km/h | 152.8 mm | Very close | Compare |
| 235/60R18 | 739.2 mm | +1.5 mm (+0.20%) | 100.2 km/h | 141.0 mm | Very close | Compare |
| 235/55R19 | 741.1 mm | +3.4 mm (+0.46%) | 100.5 km/h | 129.3 mm | Very close | Compare |
| 225/55R19 | 730.1 mm | −7.6 mm (−1.03%) | 99.0 km/h | 123.8 mm | Close | Compare |
| 265/45R20 | 746.5 mm | +8.8 mm (+1.19%) | 101.2 km/h | 119.3 mm | Close | Compare |
- Keeping your wheels, the closest is 235/60R18 at 739.2 mm, +1.5 mm (+0.20%) from the original. With the speedometer on 100 km/h, the car would actually be doing about 100.2 km/h. Ground clearance rises by about 0.8 mm.
- Moving up to 19-inch wheels, the closest height match is 255/50R19 (−0.01%), with the sidewall dropping from 140.3 mm to 127.5 mm.
- Going down to 17-inch wheels, 255/60R17 (+0.01%) is the closest match and raises the sidewall to 153.0 mm.
- A larger or wider tire also changes acceleration, fuel use and steering weight, so look beyond the percentage.
Buying 255/55R18 tires
Passenger tires in this size come in eco, comfort and sport lines. Japanese and European brands usually cost more than Asian ones, and the difference shows in noise, wet braking and tread life.
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 255/55R18
The code after the size on the sidewall, as in 255/55R18 105H, is the load index and speed symbol. The common ratings for this size:
| Version | Index | Per tire | Four tires |
|---|---|---|---|
| Standard load (SL) | 105 | 925 kg | 3,700 kg |
| Extra load (XL) | 109 | 1,030 kg | 4,120 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
H
210 km/h
V
240 km/h
255/55R18 questions
How tall is a 255/55R18 tire?
About 29.0 inches, or 737.7 mm, from top to bottom before it carries weight. Each sidewall is 140.3 mm tall and the tire is 255 mm (10.0 in) wide.
Which cars use 255/55R18 tires?
No car in our data is fitted with 255/55R18 from the factory, but its height is close to the original size on Honda CR-V, Mazda CX-5, Mitsubishi Triton and MG Extender, so it works as a replacement size.
Can I fit 235/60R18 instead of 255/55R18?
Size-wise, yes: the height differs by +0.20% (+1.5 mm), so an indicated 100 km/h is really about 100.2 km/h. The tread is 20 mm narrower. Check rim width and load index first.
How much weight can a 255/55R18 tire carry?
Most standard-load versions carry load index 105: 925 kg per tire, 3,700 kg across four. XL versions are rated 109, or 1,030 kg per tire. Look for the number after the size on the sidewall, as in 255/55R18 105H.
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.