255/40R17 · passenger car · PSI
255/40R17 tyre pressure in PSI
- Size
- 255/40R17
- Class
- passenger car
- Planning PSI
- 37
- Planning bar
- 2.55
psi
37
2.55 bar · 255 kPa · passenger car planning figure
255/40R17 · 37 psi · 2.55 bar · 255 kPa — estimates. Placard wins.
PSI is the garage-hose number. For 255/40R17 a typical passenger car planning figure is 37 psi cold — about 2.55 bar or 255 kPa. Low-profile sport or plus-size wheel. 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.
Estimated 255/40R17 pressure by load
Load moves the rear first on a passenger car. If the factory placard already has a laden column, use that — not this sketch for 255/40R17.
| 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
Use the table, then set a cold gauge. 255 kPa is 100 × 2.55 bar on this size.
| 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 |
What 255/40R17 means
Read 255/40R17 as width / aspect R rim. Nothing in the size string is a pressure. Pressure lives on the car, not moulded as 205 or 55.
Low-profile sport or plus-size wheel. Rim diameter 17 in; section 255 mm. Estimates on this page assume a typical load index for the passenger car class.
Placard versus sidewall
This website maps size searches such as “255/40R17 psi”. It does not replace the VIN label. If the two disagree, the label wins.
Cars often seen on 255/40R17
255/40R17 is a valid metric size in this register even if it is not on the curated OEM shortlist. Treat the 37 psi / 2.55 bar figure as a class estimate and confirm on the vehicle that actually wears it.
How to set 255/40R17
- Measure before the school run, not after the motorway.
- Write LF / RF / RR / RL. Do not keep 255/40R17 numbers in your head.
- Add air in short bursts toward the placard, using 37 psi only as a map.
- If one 255/40R17 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 255/40R17.
| 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 255/40R17 |
| 38 °C (heatwave tarmac) | 40 psi | 2.76 bar | 276 kPa | Do not bleed a hot 255/40R17 |
If the door sticker and this 255/40R17 page disagree, the sticker wins.
Questions about 255/40R17
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 255/40R17 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.
Is 255/40R17 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 255/40R17?
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.
What PSI should 255/40R17 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 255/40R17 and not share a sticker.
Handbook: placard · bar vs PSI · cold inflation · all sizes