245/40R18 · passenger car · kPa
248 kPa for 245/40R18 tyres
- Size
- 245/40R18
- Class
- passenger car
- Planning PSI
- 36
- Planning bar
- 2.48
kPa
248
2.48 bar · 36 psi · 100 kPa = 1 bar
245/40R18 · 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 245/40R18 (2.48 bar / 36 psi). 100 kPa = 1 bar. Wide touring 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
Convert around the 245/40R18 band. 2.48 bar is about 36 psi — not 23, not 33 unless the maths says so.
| 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 245/40R18 pressure by load
These 245/40R18 load steps are ± a few PSI from 36. They are not a licence to ignore a printed second column on a van or estate.
| Condition | Front (est.) | Rear (est.) |
|---|---|---|
| Driver only / unladen | 36 psi / 2.48 bar / 248 kPa | 36 psi / 2.48 bar / 248 kPa |
| Typical occupancy | 36 psi / 2.48 bar / 248 kPa | 37 psi / 2.55 bar / 255 kPa |
| Motorway + luggage (sketch) | 37 psi / 2.55 bar / 255 kPa | 38 psi / 2.62 bar / 262 kPa |
What 245/40R18 means
A 245/40R18 on a passenger car is a geometry. Two cars can share the size and disagree on PSI because mass and axle split differ.
Wide touring 18-inch. Rim diameter 18 in; section 245 mm. Estimates on this page assume a typical load index for the passenger car class.
Placard versus sidewall
The sidewall of a 245/40R18 may say 51 psi or 350 kPa. That is a carcass maximum. Operating pressure is the tyre-information placard on the driver’s door pillar.
Temperature drift
Roughly 1 psi per 5–6 °C. The table uses 36 psi as a 20 °C baseline for 245/40R18.
| 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 245/40R18 |
| 38 °C (heatwave tarmac) | 39 psi | 2.69 bar | 269 kPa | Do not bleed a hot 245/40R18 |
How to set 245/40R18
- Measure before the school run, not after the motorway.
- Write LF / RF / RR / RL. Do not keep 245/40R18 numbers in your head.
- Add air in short bursts toward the placard, using 36 psi only as a map.
- If one 245/40R18 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 245/40R18
These catalogue models are often seen on 245/40R18 or a close OEM neighbour. Open the vehicle chart for axle-specific PSI and bar.
Keep 245/40R18 on the printed band for that car; 36 psi is a size sketch, not a second VIN label.
Questions about 245/40R18
Can I run 245/40R18 at a lower pressure for comfort?
Not as a habit. A soft 245/40R18 cooks the shoulders and dulls steering. Keep load index and stay on the placard.
Is 245/40R18 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.
What is 245/40R18 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.
What is 245/40R18 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.
Handbook: placard · bar vs PSI · cold inflation · all sizes