235/45R18 · passenger car · kPa
235/45R18 tyre pressure in kPa
- Size
- 235/45R18
- Class
- passenger car
- Planning PSI
- 36
- Planning bar
- 2.48
kPa
248
2.48 bar · 36 psi · 100 kPa = 1 bar
235/45R18 · 36 psi · 2.48 bar · 248 kPa — estimates. Placard wins.
Kilopascals show up on some Asian stickers and ISO sheets. 248 kPa is the planning midpoint for 235/45R18 (2.48 bar / 36 psi). 100 kPa = 1 bar. Common EV / sport 18-inch. These rows are estimates interpolated for the size, not OEM for a named VIN. Low-profile {sz} does not want a “softer” pressure to recover ride. Stay at or slightly above the car’s original placard if load index is kept.
kPa, bar and PSI
1 bar ≈ 14.5 psi; 1 psi ≈ 6.89 kPa. Planning midpoint for 235/45R18: 36 psi = 2.48 bar = 248 kPa.
| kPa | Bar | PSI |
|---|---|---|
| 221 | 2.21 | 32 |
| 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 |
Estimated 235/45R18 pressure by load
Plus-sizing to 235/45R18 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 | 36 psi / 2.48 bar / 248 kPa | 36 psi / 2.48 bar / 248 kPa |
| Typical occupancy | 37 psi / 2.55 bar / 255 kPa | 38 psi / 2.62 bar / 262 kPa |
| Motorway + luggage (sketch) | 38 psi / 2.62 bar / 262 kPa | 39 psi / 2.69 bar / 269 kPa |
What 235/45R18 means
Read 235/45R18 as width / aspect R rim. Nothing in the size string is a pressure. Pressure lives on the car, not moulded as 205 or 55.
Common EV / sport 18-inch. Rim diameter 18 in; section 235 mm. Estimates on this page assume a typical load index for the passenger car class.
Placard versus sidewall
If a forum says “all 235/45R18 run 36 psi”, ignore it. A Qashqai and a Golf can share a size and not share a sticker.
Temperature drift
Roughly 1 psi per 5–6 °C. The table uses 36 psi as a 20 °C baseline for 235/45R18.
| Ambient | Gauge | Bar | kPa | Note |
|---|---|---|---|---|
| −5 °C (hard frost) | 33 psi | 2.28 bar | 228 kPa | Gauge reads low; do not overfill once warm |
| 0 °C | 34 psi | 2.34 bar | 234 kPa | Gauge reads low; do not overfill once warm |
| 8 °C (UK winter morning) | 35 psi | 2.41 bar | 241 kPa | Gauge reads low; do not overfill once warm |
| 20 °C (set cold here) | 36 psi | 2.48 bar | 248 kPa | Baseline for this size sketch |
| 30 °C | 38 psi | 2.62 bar | 262 kPa | Do not bleed a hot 235/45R18 |
| 38 °C (heatwave tarmac) | 39 psi | 2.69 bar | 269 kPa | Do not bleed a hot 235/45R18 |
How to set 235/45R18
- Measure before the school run, not after the motorway.
- Write LF / RF / RR / RL. Do not keep 235/45R18 numbers in your head.
- Add air in short bursts toward the placard, using 36 psi only as a map.
- If one 235/45R18 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 235/45R18
These catalogue models are often seen on 235/45R18 or a close OEM neighbour. Open the vehicle chart for axle-specific PSI and bar.
Keep 235/45R18 on the printed band for that car; 36 psi is a size sketch, not a second VIN label.
Questions about 235/45R18
What PSI should 235/45R18 tyres be?
A passenger car planning figure is about 36 psi cold (2.48 bar / 248 kPa). Confirm on the vehicle placard — two cars can share 235/45R18 and not share a sticker.
What is 235/45R18 in bar?
36 psi is 2.48 bar. Add a tenth of a bar if the placard’s laden column is higher, which is common on vans that wear this size.
Can I run 235/45R18 at a lower pressure for comfort?
Not as a habit. A soft 235/45R18 cooks the shoulders and dulls steering. Keep load index and stay on the placard.
What is 235/45R18 in kPa?
248 kPa is the planning midpoint (100 kPa = 1 bar). 255 kPa is one PSI higher.
Should I bleed pressure after a motorway run?
No. Heat raises the gauge. Set cold only. Bleeding a hot tyre leaves it low the next morning.
Handbook: placard · bar vs PSI · cold inflation · all sizes