Proton · 315 · Cold
Proton 315 cold-inflation guide
- Drivetrain
- front-wheel drive
- Body
- passenger car
- PSI F / R
- 32-35 / 32-35
- Bar F / R
- 2.2-2.4 / 2.2-2.4
psi
34 / 34
Catalogue mid-points, front / rear · 2.2-2.4 / 2.2-2.4 bar
32-35 psi F · 32-35 psi R · 2.2-2.4 / 2.2-2.4 bar · 231/231 kPa
Cold means the Proton 315 has stood at least three hours, or covered less than about a mile. Heat from a dual carriageway run is not the number you set. Size estimates on this page include 245/40R18, 225/50R17 and 215/55R16 — interpolated from the catalogue midpoint, not a second factory sticker.
Temperature and a cold gauge
Roughly 1 psi per 5–6 °C. The table uses 34 psi as a 20 °C baseline for this 315.
| Ambient | Gauge (front mid) | Bar | kPa | Note |
|---|---|---|---|---|
| −5 °C (hard frost) | 31 psi | 2.14 bar | 214 kPa | Gauge reads low; do not overfill once warm |
| 0 °C | 32 psi | 2.21 bar | 221 kPa | Gauge reads low; do not overfill once warm |
| 8 °C (UK winter morning) | 33 psi | 2.28 bar | 228 kPa | Gauge reads low; do not overfill once warm |
| 20 °C (set cold here) | 34 psi | 2.34 bar | 234 kPa | Baseline |
| 30 °C | 36 psi | 2.48 bar | 248 kPa | Do not bleed a hot tyre |
| 38 °C (heatwave tarmac) | 37 psi | 2.55 bar | 255 kPa | Do not bleed a hot tyre |
How to set the 315
- Measure before the school run, not after the M25.
- Write LF / RF / RR / RL. Do not keep 315 numbers in your head.
- Add air in short bursts toward 34 psi (2.31 bar) front and 34 psi rear.
- If one corner is 4 psi down, hunt for a nail before you blame the weather.
- Log date, ambient temperature and the four readings.
Proton 315 placard versus sidewall
If the Proton sticker is painted over, the handbook is next. This website is a map, not a replacement VIN label.
Estimated pressure by tyre size (245/40R18 and others)
Planning cold pressures for sizes often seen on a passenger car. This 315 sample opens with 245/40R18, then 225/50R17 and 215/55R16.
| Tyre size | Front PSI | Rear PSI | Front bar | Rear bar | Front kPa | Rear kPa | Note |
|---|---|---|---|---|---|---|---|
| 245/40R18 | 36 | 36 | 2.48 | 2.48 | 248 | 248 | Wide touring 18-inch |
| 225/50R17 | 35 | 35 | 2.41 | 2.41 | 241 | 241 | Touring 17-inch |
| 215/55R16 | 34 | 35 | 2.34 | 2.41 | 234 | 241 | Slightly wider 16-inch |
| 215/50R17 | 35 | 35 | 2.41 | 2.41 | 241 | 241 | Plus-size 17-inch |
| 205/55R16 | 34 | 34 | 2.34 | 2.34 | 234 | 234 | Typical mid-compact OEM |
| 205/60R16 | 34 | 34 | 2.34 | 2.34 | 234 | 234 | Taller 16-inch |
| 225/45R17 | 35 | 35 | 2.41 | 2.41 | 241 | 241 | Sport 17-inch |
| 225/40R18 | 36 | 36 | 2.48 | 2.48 | 248 | 248 | Low-profile 18-inch |
PSI, bar and kPa
PSI-led conversions for the Proton 315 band (32-35 / 32-35).
| PSI | Bar | kPa |
|---|---|---|
| 30 | 2.07 | 207 |
| 32 | 2.21 | 221 |
| 33 | 2.28 | 228 |
| 33.5 | 2.31 | 231 |
| 35 | 2.41 | 241 |
| 36 | 2.48 | 248 |
| 38 | 2.62 | 262 |
| 40 | 2.76 | 276 |
| 44 | 3.03 | 303 |
| 50 | 3.45 | 345 |
| 60 | 4.14 | 414 |
Load notes
Load moves the rear of a passenger car first. If the factory placard already has a “laden” column, use that instead of these sketches.
| Condition | Front (est.) | Rear (est.) |
|---|---|---|
| Driver only | 34 psi / 2.34 bar | 34 psi / 2.34 bar |
| Full occupancy | 35 psi / 2.41 bar | 36 psi / 2.48 bar |
| Motorway + luggage | 36 psi / 2.48 bar | 37 psi / 2.55 bar |
Proton notes
No special Proton exception: the 315 uses the door-pillar placard. Size estimates on this page only help if you have left the original load index behind.
Spare and inflator kit
A matching full-size spare on the Proton 315 usually follows the higher axle (often the rear, near 32-35 psi). A space-saver is commonly 60 psi / 4.1 bar — read that tyre’s own sidewall. An inflator kit is not a spare; check the sealant date.
If the Proton sticker and this page disagree, the sticker wins.
Other Proton models
Questions about this 315
Front versus rear on the Proton 315?
This row is 32-35 F / 32-35 R. Even when they match, a laden rear can justify a higher number if the sticker prints one.
How often should I check a 315?
Monthly, before a long trip, and after a 10 °C weather swing. Include a full-size spare.
What tyre pressure should a Proton 315 use?
Catalogue reference is 32-35 psi front and 32-35 psi rear (2.2-2.4 / 2.2-2.4 bar), cold. Confirm on the door-pillar placard.
Is the sidewall number correct on a Proton 315?
No. Sidewall PSI is a maximum. The 315 placard is the operating target, near 32-35/32-35 psi.
What PSI if I plus-size toward 215/55R16?
Keep load index at or above OEM. Low-profile sizes usually stay at or slightly above the placard. Use 245/40R18, 225/50R17 and 215/55R16 as a planning band.
Handbook: placard · bar vs PSI · front vs rear · cold inflation