Rear tyre anomaly

[Tight Git]

This is odd. When I fiddled with the pressures I thought I'd got them to about 2.5 cold rising to 2.6 warm. But then once they were cold again they were still reading 2.6.

The car hasn't turned a wheel for nearly 48 hours. It's just been sitting on my drive. When I went to check, three tyres were showing 2.7. (The one I thought was fractionally lower is still on 2.6.) This might be a bit high? Why so high when everything is cold?

The car remembers the pressures when it was last awake - it doesn't update until you have driven a few minutes.

 

[Rolfe]

Ah, I didn't think of that. That would explain it.

 

[siteguru]

Thanks all - I'm going to try putting both rears at 2.6 then (i thought it said 2.5 bar somewhere). Also going to investigate if can turn the annoying lady voice off !

The manual says 37 psi, which is 2.55 bar (which rounds up to 2.6 bar). The driver display (and the app) would be better if it showed tyre pressure to 2 decimal places. (Or gave an option to select psi vs bar)

 

[Rolfe]

To be fair, we only use two significant figures when working in psi.

 

[fnegroni]

I think 37 psi cold gives a harsh ride and lowers grip in the rear.

I find for spirited driving in summer I put 33 psi rear and 34 psi front

 

[MG Fred]

mine was doing it last autumn when I first got the car . went into the dealers for the tpms to be reset. Was fine all winter Spring and Summer , now started again . At the moment as others have said once the air in the tyre ( atm it's only the rear offside) has heated up[ a bit , it's fine .

It used to be a requirement to regularly check tyre pressures, now we have TMPS sensors to do that for us, but you still have to pump them up now and again, all tyres loose a very small amount over time. It shouldn‘t be a dealer visit to pump up tyres. If it’s at 2.3 bar then it’s 10% low and needs pumping back up.

 

[siteguru]

To be fair, we only use two significant figures when working in psi.

Yes, but psi is a much more granular measurement than bar (1 bar = 14.7 psi) so having no decimal places is fine; 0.1 bar = 1.47 psi - so quite a difference in pressure between 2.5 and 2.6 bar.

 

[NickHeynes]

Not sure what you mean about resetting the system - it automatically resets when you drive after reinflating. There's no need for a manual reset.

I didn't know that . What does it set to? 2.6 bar?

 

[siteguru]

A system reset usually refers to resetting the warning/alert, not the alert setpoint ... the MG4 does it automatically.

 

[tsedge]

I didn't know that . What does it set to? 2.6 bar?

Ah, you mean the pressure target. As far as I know you can't change this yourself but I presume a dealer can - it must be an OBD available setting I would think.

The threshold for an alarm seems to be around 2.4 bar, below that it goes off.

 

[TorvaFirmus]

I have only seen this once. When the tyre pressure on the rear tyres dropped from 2.5 to 2.4. The front tyres stayed at 2.5. I have since seen all the tyre pressures drop to 2.4 while driving without any warning. I have not added any air to the tyres.