225/40R17 · passenger car · Overview
225/40R17 tyre pressure
- Size
- 225/40R17
- Class
- passenger car
- Planning PSI
- 36
- Planning bar
- 2.48
225/40R17
36 psi / 2.48 bar
248 kPa · estimates for this size class
225/40R17 · 36 psi · 2.48 bar · 248 kPa — estimates. Placard wins.
Searches for “225/40R17 pressure” usually want a number. Use 36 psi (2.48 bar) only as a sketch; the door-pillar placard on the car that wears this size still wins. A 10 °C overnight drop takes roughly 1 psi (0.07 bar) off a closed 225/40R17. 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 225/40R17 means
Read 225/40R17 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 17-inch. Rim diameter 17 in; section 225 mm. Estimates on this page assume a typical load index for the passenger car class.
Estimated 225/40R17 pressure by load
Plus-sizing to 225/40R17 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 | 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 |
PSI, bar and kPa
1 bar ≈ 14.5 psi; 1 psi ≈ 6.89 kPa. Planning midpoint for 225/40R17: 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 |
Placard versus sidewall
The sidewall of a 225/40R17 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 225/40R17
These catalogue models are often seen on 225/40R17 or a close OEM neighbour. Open the vehicle chart for axle-specific PSI and bar.
How to set 225/40R17
- Measure before the school run, not after the motorway.
- Write LF / RF / RR / RL. Do not keep 225/40R17 numbers in your head.
- Add air in short bursts toward the placard, using 36 psi only as a map.
- If one 225/40R17 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 36 psi as a 20 °C baseline for 225/40R17.
| 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 225/40R17 |
| 38 °C (heatwave tarmac) | 39 psi | 2.69 bar | 269 kPa | Do not bleed a hot 225/40R17 |
Keep 225/40R17 on the printed band for that car; 36 psi is a size sketch, not a second VIN label.
Questions about 225/40R17
What is 225/40R17 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.
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.
Can I run 225/40R17 at a lower pressure for comfort?
Not as a habit. A soft 225/40R17 cooks the shoulders and dulls steering. Keep load index and stay on the placard.
Is 225/40R17 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.
What PSI should 225/40R17 tyres be?
A passenger car planning figure is about 36 psi cold (2.48 bar / 248 kPa). Confirm on the vehicle placard — two cars can share 225/40R17 and not share a sticker.
Handbook: placard · bar vs PSI · cold inflation · all sizes