255/35R20 · passenger car · kPa
255/35R20 kPa inflation table
- Size
- 255/35R20
- Class
- passenger car
- Planning PSI
- 37
- Planning bar
- 2.55
kPa
255
2.55 bar · 37 psi · 100 kPa = 1 bar
255/35R20 · 37 psi · 2.55 bar · 255 kPa — estimates. Placard wins.
If the gauge only speaks kPa, 255 kPa is the sketch for this passenger car size. Fine-tune to the vehicle that actually wears 255/35R20. Under-inflation cooks the shoulders of a 255/35R20; over-inflation wears the centre rib and bangs every cat’s eye. 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 255/35R20: 37 psi = 2.55 bar = 255 kPa.
| 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 255/35R20 pressure by load
Plus-sizing to 255/35R20 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 255/35R20 means
Read 255/35R20 as width / aspect R rim. Nothing in the size string is a pressure. Pressure lives on the car, not moulded as 205 or 55.
20-inch plus-size car. Rim diameter 20 in; section 255 mm. Estimates on this page assume a typical load index for the passenger car class.
Placard versus sidewall
The sidewall of a 255/35R20 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 37 psi as a 20 °C baseline for 255/35R20.
| 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 255/35R20 |
| 38 °C (heatwave tarmac) | 40 psi | 2.76 bar | 276 kPa | Do not bleed a hot 255/35R20 |
How to set 255/35R20
- Measure before the school run, not after the motorway.
- Write LF / RF / RR / RL. Do not keep 255/35R20 numbers in your head.
- Add air in short bursts toward the placard, using 37 psi only as a map.
- If one 255/35R20 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 255/35R20
These catalogue models are often seen on 255/35R20 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 255/35R20 than nitrogen upsells.
Questions about 255/35R20
Is 255/35R20 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 255/35R20 in bar?
37 psi is 2.55 bar. Add a tenth of a bar if the placard’s laden column is higher, which is common on vans that wear this size.
What is 255/35R20 in kPa?
255 kPa is the planning midpoint (100 kPa = 1 bar). 262 kPa is one PSI higher.
Is the sidewall number correct for 255/35R20?
No. Sidewall PSI or kPa is a maximum for the carcass. Operating pressure is the door-pillar 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.
Handbook: placard · bar vs PSI · cold inflation · all sizes