275/35R18 · passenger car · kPa
275/35R18 kPa inflation table
- Size
- 275/35R18
- Class
- passenger car
- Planning PSI
- 37
- Planning bar
- 2.55
kPa
255
2.55 bar · 37 psi · 100 kPa = 1 bar
275/35R18 · 37 psi · 2.55 bar · 255 kPa — estimates. Placard wins.
Kilopascals show up on some Asian stickers and ISO sheets. 255 kPa is the planning midpoint for 275/35R18 (2.55 bar / 37 psi). 100 kPa = 1 bar. TPMS typically warns near 28 psi (about 25% below a 37 psi target). That is already a soft tyre.
kPa, bar and PSI
Convert around the 275/35R18 band. 2.55 bar is about 37 psi — not 23, not 33 unless the maths says so.
| kPa | Bar | PSI |
|---|---|---|
| 228 | 2.28 | 33 |
| 234 | 2.34 | 34 |
| 241 | 2.41 | 35 |
| 248 | 2.48 | 36 |
| 255 | 2.55 | 37 |
| 262 | 2.62 | 38 |
| 269 | 2.69 | 39 |
| 276 | 2.76 | 40 |
| 283 | 2.83 | 41 |
| 290 | 2.90 | 42 |
| 296 | 2.96 | 43 |
| 303 | 3.03 | 44 |
| 310 | 3.10 | 45 |
| 317 | 3.17 | 46 |
| 324 | 3.24 | 47 |
| 331 | 3.31 | 48 |
| 338 | 3.38 | 49 |
Estimated 275/35R18 pressure by load
Plus-sizing to 275/35R18 from a taller OEM tyre usually keeps the same placard if the load index is equal or higher.
| Condition | Front (est.) | Rear (est.) |
|---|---|---|
| Driver only / unladen | 37 psi / 2.55 bar / 255 kPa | 37 psi / 2.55 bar / 255 kPa |
| Typical occupancy | 38 psi / 2.62 bar / 262 kPa | 39 psi / 2.69 bar / 269 kPa |
| Motorway + luggage (sketch) | 39 psi / 2.69 bar / 269 kPa | 40 psi / 2.76 bar / 276 kPa |
What 275/35R18 means
A 275/35R18 on a passenger car is a geometry. Two cars can share the size and disagree on PSI because mass and axle split differ.
Wide rear 18-inch. Rim diameter 18 in; section 275 mm. Estimates on this page assume a typical load index for the passenger car class.
Placard versus sidewall
This website maps size searches such as “275/35R18 psi”. It does not replace the VIN label. If the two disagree, the label wins.
Temperature drift
Roughly 1 psi per 5–6 °C. The table uses 37 psi as a 20 °C baseline for 275/35R18.
| Ambient | Gauge | Bar | kPa | Note |
|---|---|---|---|---|
| −5 °C (hard frost) | 34 psi | 2.34 bar | 234 kPa | Gauge reads low; do not overfill once warm |
| 0 °C | 35 psi | 2.41 bar | 241 kPa | Gauge reads low; do not overfill once warm |
| 8 °C (UK winter morning) | 36 psi | 2.48 bar | 248 kPa | Gauge reads low; do not overfill once warm |
| 20 °C (set cold here) | 37 psi | 2.55 bar | 255 kPa | Baseline for this size sketch |
| 30 °C | 39 psi | 2.69 bar | 269 kPa | Do not bleed a hot 275/35R18 |
| 38 °C (heatwave tarmac) | 40 psi | 2.76 bar | 276 kPa | Do not bleed a hot 275/35R18 |
How to set 275/35R18
- Measure before the school run, not after the motorway.
- Write LF / RF / RR / RL. Do not keep 275/35R18 numbers in your head.
- Add air in short bursts toward the placard, using 37 psi only as a map.
- If one 275/35R18 is 4 psi down, hunt for a nail before you blame the weather.
- Log date, ambient temperature and the four readings.
Cars often seen on 275/35R18
These catalogue models are often seen on 275/35R18 or a close OEM neighbour. Open the vehicle chart for axle-specific PSI and bar.
A cheap gauge and a monthly habit will do more for a set of 275/35R18 than nitrogen upsells.
Questions about 275/35R18
What is 275/35R18 in kPa?
255 kPa is the planning midpoint (100 kPa = 1 bar). 262 kPa is one PSI higher.
Is the sidewall number correct for 275/35R18?
No. Sidewall PSI or kPa is a maximum for the carcass. Operating pressure is the door-pillar placard.
What PSI should 275/35R18 tyres be?
A passenger car planning figure is about 37 psi cold (2.55 bar / 255 kPa). Confirm on the vehicle placard — two cars can share 275/35R18 and not share a sticker.
Can I run 275/35R18 at a lower pressure for comfort?
Not as a habit. A soft 275/35R18 cooks the shoulders and dulls steering. Keep load index and stay on the placard.
Is 275/35R18 the same as a plus-size swap?
Only if that is the size you fitted. Overall diameter should stay close to OEM. Pressure still follows the car, with load index at or above original.
Handbook: placard · bar vs PSI · cold inflation · all sizes