Tyre pressure warning light

bakerdave

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Sep 30, 2025
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Penarth
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MG3 Hybrid+
Another newbie question - what are the tolerances on the tyre pressures ? Today, drove to get petrol and noticed on the way back, that there were alarm symbols up. Stopped in a layby to consult the (enormous) manual to find that the right front was showing 2.4 bar . Just wondering whether to pump up to 38psi but will that alarm high ? The readout is showing 2.4 bar on the right rear but no alarm!
 
Another newbie question - what are the tolerances on the tyre pressures ? Today, drove to get petrol and noticed on the way back, that there were alarm symbols up. Stopped in a layby to consult the (enormous) manual to find that the right front was showing 2.4 bar . Just wondering whether to pump up to 38psi but will that alarm high ? The readout is showing 2.4 bar on the right rear but no alarm!
Hi, mine came on last week when it was very cold. I inflated all to 37psi and after driving a short distance, the warning switched off. All still OK and showing 37.8 psi on all four tyres. The warnings remain in the iSmart app until you delete them.
 
Hi, mine came on last week when it was very cold. I inflated all to 37psi and after driving a short distance, the warning switched off. All still OK and showing 37.8 psi on all four tyres. The warnings remain in the iSmart app until you delete them.
According to the pressure guide on the door pillar 38lb PSi pressure is the recommendation, which equates to 2.6 bar.
 
According to the pressure guide on the door pillar 38lb PSi pressure is the recommendation, which equates to 2.6 bar.
True 👍 I set mine to 37 psi as it was a very cold morning and I knew the pressure would increase as normal temperatures were reached. Not a bad guess, as they're now at 37.8 psi!
 
i only had mine since May. so far i found the tyre pressure monitoring is off by as much as 3psi in hotter weather (we had 30-35degC in London this summer) but now the weather is hovering around 10-20degC, it's matching my calibrated guage again (i have one at work). in summer the air pressure reads 39psi but when i use my calibrated gauge, it says it's around 36psi. there was one morning that suddenly drops to 5degC and the pressure drops to 32psi and the car starts to give me warning. after experimenting with the tyre pressure, for 10-20degC, i settle for 35psi (at this temperature, the calibrated gauge agrees with the onboard monitor). [mind you, im no longer using the OEM tyres, i have Goodyear Vector4 Seasons, same dimension but reinforced sidewalls, so probably ok with slightly lower pressure like 1-2psi lower than recommended]
 
I had my first service a couple of weeks ago. However the other day, about 5 km from home the WARNING light came on suggesting that the front right tyre had lost pressure. I stopped and checked the tyres. All was fine. I went directly to the MG dealer and they said it was a known problem and that, provided the tyres are OK and up to pressure then do not worry. The warning has not returned so I am left wondering what on earth happened to cause it.
 
If the tyre pressures are okay the warning light shouldn't come on, so it sounds like one of the tyre pressure sensors received a false signal from the computer especially if the warning light hasn't lit up again
 
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