Martin Motors · MM520 · Bar
Martin Motors MM520 bar chart (2.2-2.4 / 2.2-2.4)
- 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
bar
2.31 / 2.31
32-35 / 32-35 psi · 231 / 231 kPa
32-35 psi F · 32-35 psi R · 2.2-2.4 / 2.2-2.4 bar · 231/231 kPa
2.3 bar is not 23 psi. On this MM520 2.2-2.4 bar converts to about 32-35 psi. Use the table, not a guess. TPMS typically warns near 25 psi (about 25% below target). That is already a soft tyre, not a fill target.
Bar, PSI and kPa
Bar-led conversions around the Martin Motors MM520. 2.2-2.4 bar is not “32-35 divided by ten”.
| Bar | PSI | kPa |
|---|---|---|
| 2.07 | 30 | 207 |
| 2.21 | 32 | 221 |
| 2.28 | 33 | 228 |
| 2.31 | 33.5 | 231 |
| 2.41 | 35 | 241 |
| 2.48 | 36 | 248 |
| 2.62 | 38 | 262 |
| 2.76 | 40 | 276 |
| 3.03 | 44 | 303 |
| 3.45 | 50 | 345 |
| 4.14 | 60 | 414 |
Martin Motors MM520 placard versus sidewall
Sidewall PSI is a carcass maximum. Recommended operating pressure for this MM520 is the pillar sticker, near 34/34 psi.
Estimated pressure by tyre size (245/40R18 and others)
If your Martin Motors MM520 no longer wears the OEM diameter, start at the row nearest 245/40R18 or 275/35R18 and confirm with the tyre maker’s load table.
| Tyre size | Front PSI | Rear PSI | Front bar | Rear bar | Front kPa | Rear kPa | Note |
|---|---|---|---|---|---|---|---|
| 245/40R18 | 35 | 36 | 2.41 | 2.48 | 241 | 248 | Square-ish sport |
| 275/35R18 | 36 | 37 | 2.48 | 2.55 | 248 | 255 | Wide rear |
| 235/35R19 | 36 | 36 | 2.48 | 2.48 | 248 | 248 | Front 19-inch |
| 225/45R17 | 34 | 35 | 2.34 | 2.41 | 234 | 241 | Front sport size |
| 225/40R18 | 35 | 35 | 2.41 | 2.41 | 241 | 241 | Front 18-inch |
| 255/35R18 | 35 | 36 | 2.41 | 2.48 | 241 | 248 | Rear stagger 18-inch |
| 275/30R19 | 36 | 37 | 2.48 | 2.55 | 248 | 255 | Rear 19-inch |
| 255/40R17 | 35 | 36 | 2.41 | 2.48 | 241 | 248 | Rear stagger 17-inch |
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 | 34 psi / 2.34 bar | 35 psi / 2.41 bar |
| Motorway + luggage | 35 psi / 2.41 bar | 36 psi / 2.48 bar |
How to set the MM520
- Park the Martin Motors MM520 for at least three hours (cold tyres).
- Use a calibrated gauge, not the only meter on a forecourt hose.
- Set the placard for that axle — about 32-35 psi / 2.2-2.4 bar front and 32-35 psi / 2.2-2.4 bar rear on this catalogue row.
- Recheck all four. A 2 psi miss on a front-wheel drive MM520 is enough to feel a pull.
- Refit valve caps and reset TPMS if the handbook asks for a relearn.
Temperature drift
Roughly 1 psi per 5–6 °C. The table uses 34 psi as a 20 °C baseline for this MM520.
| 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 |
Martin Motors notes
No special Martin Motors exception: the MM520 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 Martin Motors MM520 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.
A cheap gauge and a monthly habit will do more for this MM520 than nitrogen upsells.
Other Martin Motors models
Questions about this MM520
Front versus rear on the Martin Motors MM520?
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.
What PSI if I plus-size toward 235/35R19?
Keep load index at or above OEM. Low-profile sizes usually stay at or slightly above the placard. Use 245/40R18, 275/35R18 and 235/35R19 as a planning band.
What tyre pressure should a Martin Motors MM520 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 Martin Motors MM520?
No. Sidewall PSI is a maximum. The MM520 placard is the operating target, near 32-35/32-35 psi.
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 · front vs rear · cold inflation