255/40R19 · passenger car · Overview
Recommended pressure for 255/40R19 tyres
- Size
- 255/40R19
- Class
- passenger car
- Planning PSI
- 37
- Planning bar
- 2.55
255/40R19
37 psi / 2.55 bar
255 kPa · estimates for this size class
255/40R19 · 37 psi · 2.55 bar · 255 kPa — estimates. Placard wins.
Searches for “255/40R19 pressure” usually want a number. Use 37 psi (2.55 bar) only as a sketch; the door-pillar placard on the car that wears this size still wins. Under-inflation cooks the shoulders of a 255/40R19; 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.
What 255/40R19 means
Read 255/40R19 as width / aspect R rim. Nothing in the size string is a pressure. Pressure lives on the car, not moulded as 205 or 55.
EV 19-inch aero wheel. Rim diameter 19 in; section 255 mm. Estimates on this page assume a typical load index for the passenger car class.
Estimated 255/40R19 pressure by load
These 255/40R19 load steps are ± a few PSI from 37. They are not a licence to ignore a printed second column on a van or estate.
| Condition | Front (est.) | Rear (est.) |
|---|---|---|
| Driver only / unladen | 37 psi / 2.55 bar / 255 kPa | 37 psi / 2.55 bar / 255 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 |
PSI, bar and kPa
1 bar ≈ 14.5 psi; 1 psi ≈ 6.89 kPa. Planning midpoint for 255/40R19: 37 psi = 2.55 bar = 255 kPa.
| PSI | Bar | kPa |
|---|---|---|
| 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 |
| 49 | 3.38 | 338 |
Placard versus sidewall
The sidewall of a 255/40R19 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 255/40R19
These catalogue models are often seen on 255/40R19 or a close OEM neighbour. Open the vehicle chart for axle-specific PSI and bar.
How to set 255/40R19
- Measure before the school run, not after the motorway.
- Write LF / RF / RR / RL. Do not keep 255/40R19 numbers in your head.
- Add air in short bursts toward the placard, using 37 psi only as a map.
- If one 255/40R19 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 37 psi as a 20 °C baseline for 255/40R19.
| 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 255/40R19 |
| 38 °C (heatwave tarmac) | 40 psi | 2.76 bar | 276 kPa | Do not bleed a hot 255/40R19 |
Keep 255/40R19 on the printed band for that car; 37 psi is a size sketch, not a second VIN label.
Questions about 255/40R19
What is 255/40R19 in kPa?
255 kPa is the planning midpoint (100 kPa = 1 bar). 262 kPa is one PSI higher.
Can I run 255/40R19 at a lower pressure for comfort?
Not as a habit. A soft 255/40R19 cooks the shoulders and dulls steering. Keep load index and stay on the placard.
What PSI should 255/40R19 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 255/40R19 and not share a sticker.
Is 255/40R19 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.
When does TPMS warn on 255/40R19?
Direct TPMS typically flags about 25% below target — near 28 psi if you were aiming at 37. Fill to the sticker, not to the lamp.
Handbook: placard · bar vs PSI · cold inflation · all sizes