255/45R20 · SUV / crossover · PSI
What PSI for 255/45R20 tyres?
- Size
- 255/45R20
- Class
- SUV / crossover
- Planning PSI
- 36
- Planning bar
- 2.48
psi
36
2.48 bar · 248 kPa · SUV / crossover planning figure
255/45R20 · 36 psi · 2.48 bar · 248 kPa — estimates. Placard wins.
If someone typed “255/45R20 psi”, they want Imperial. Start near 36 psi on an unladen SUV / crossover, then confirm the vehicle placard. Sidewall max is not the target. Under-inflation cooks the shoulders of a 255/45R20; over-inflation wears the centre rib and bangs every cat’s eye.
Estimated 255/45R20 pressure by load
Load moves the rear first on a SUV / crossover. If the factory placard already has a laden column, use that — not this sketch for 255/45R20.
| Condition | Front (est.) | Rear (est.) |
|---|---|---|
| Driver only / unladen | 36 psi / 2.48 bar / 248 kPa | 38 psi / 2.62 bar / 262 kPa |
| Typical occupancy | 36 psi / 2.48 bar / 248 kPa | 39 psi / 2.69 bar / 269 kPa |
| Motorway + luggage (sketch) | 37 psi / 2.55 bar / 255 kPa | 40 psi / 2.76 bar / 276 kPa |
PSI, bar and kPa
1 bar ≈ 14.5 psi; 1 psi ≈ 6.89 kPa. Planning midpoint for 255/45R20: 36 psi = 2.48 bar = 248 kPa.
| PSI | Bar | kPa |
|---|---|---|
| 32 | 2.21 | 221 |
| 33 | 2.28 | 228 |
| 34 | 2.34 | 234 |
| 35 | 2.41 | 241 |
| 36 | 2.48 | 248 |
| 37 | 2.55 | 255 |
| 38 | 2.62 | 262 |
| 39 | 2.69 | 269 |
| 40 | 2.76 | 276 |
| 41 | 2.83 | 283 |
| 42 | 2.90 | 290 |
| 43 | 2.96 | 296 |
| 44 | 3.03 | 303 |
| 45 | 3.10 | 310 |
| 46 | 3.17 | 317 |
| 47 | 3.24 | 324 |
| 48 | 3.31 | 331 |
What 255/45R20 means
255/45R20 means a 255 millimetre section width, a sidewall that is 45 percent of that width, on a 20-inch rim. The R is radial construction.
20-inch SUV. Rim diameter 20 in; section 255 mm. Estimates on this page assume a typical load index for the SUV / crossover class.
Placard versus sidewall
The sidewall of a 255/45R20 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.
Cars often seen on 255/45R20
These catalogue models are often seen on 255/45R20 or a close OEM neighbour. Open the vehicle chart for axle-specific PSI and bar.
How to set 255/45R20
- Measure before the school run, not after the motorway.
- Write LF / RF / RR / RL. Do not keep 255/45R20 numbers in your head.
- Add air in short bursts toward the placard, using 36 psi only as a map.
- If one 255/45R20 is 4 psi down, hunt for a nail before you blame the weather.
- Log date, ambient temperature and the four readings.
Temperature drift
Roughly 1 psi per 5–6 °C. The table uses 36 psi as a 20 °C baseline for 255/45R20.
| 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 255/45R20 |
| 38 °C (heatwave tarmac) | 39 psi | 2.69 bar | 269 kPa | Do not bleed a hot 255/45R20 |
Keep 255/45R20 on the printed band for that car; 36 psi is a size sketch, not a second VIN label.
Questions about 255/45R20
Can I run 255/45R20 at a lower pressure for comfort?
Not as a habit. A soft 255/45R20 cooks the shoulders and dulls steering. Keep load index and stay on the placard.
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 255/45R20 in kPa?
248 kPa is the planning midpoint (100 kPa = 1 bar). 255 kPa is one PSI higher.
What is 255/45R20 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.
Is the sidewall number correct for 255/45R20?
No. Sidewall PSI or kPa is a maximum for the carcass. Operating pressure is the door-pillar placard.
Handbook: placard · bar vs PSI · cold inflation · all sizes