MG ZS EV Tyre Pressure

[Kithmo]

I've put Nitrogen in my tyres for years, first on my leaf and then my MG5. The theory goes it saves you money in ICE cars, though the rational (reduced weight of fuel) doesn't hold up in an EV obviously. But for me I know the importance of having the correct pressure in tyres so Nitrogen scores here too as the atoms are larger so cannot seep through the pores of the tyre, thus virtually no leak.
A local tyre garage here charges £2.50 per tyre then every 3 months he says come back to get checked and top ups are free.
Ive been doing this since 2017 and I'd say the number of times they've topped up is in single figures

I could never see the point, air is 78% nitrogen already.
In theory if you let the oxygen (and other smaller atoms of whatever) leak through the tyre you have already got 100% nitrogen at a lower pressure. If you then top up and repeat, after a few top ups you end up with almost 100% nitrogen in your tyres naturally.
I wouldn't trust that the garage is using pure nitrogen when they put it in and when they top it up, they may be using 78% nitrogen, in other words, air.
I've still got the original air in my 2.5 year old ZS and only topped up once.

 

[Archev]

Not sure your logic holds up here. Air is 78% nitrogen and 21% oxygen. A molecule of nitrogen is 300 picometres and oxygen is 292 picometres, so putting air in your tyres will have the same effect as just putting in nitrogen.

Interestingly I worked with expansion vessels on central heating and unvented hot water systems for many years. The vessels are steel with a flexible balloon or diaphragm internally and a shrader valve just like a car tyre. The vessels are inflated and take up the expansion as the water heats and cools in the pipework. These vessels are supplied pressurised with nitrogen. Through time they lose a bit of that pressure, manifested usually by the system overflow dripping.
The manufacturers recommend re-charging with nitrogen.

I could never see the point, air is 78% nitrogen already.
In theory if you let the oxygen (and other smaller atoms of whatever) leak through the tyre you have already got 100% nitrogen at a lower pressure. If you then top up and repeat, after a few top ups you end up with almost 100% nitrogen in your tyres naturally.
I wouldn't trust that the garage is using pure nitrogen when they put it in and when they top it up, they may be using 78% nitrogen, in other words, air.
I've still got the original air in my 2.5 year old ZS and only topped up once.

Ooh you little cynic - you’ll be suggesting plumbers use air pumps on your heating/ hot water systems next

 

[Gadget Geek]

Interestingly I worked with expansion vessels on central heating and unvented hot water systems for many years. The vessels are steel with a flexible balloon or diaphragm internally and a shrader valve just like a car tyre. The vessels are inflated and take up the expansion as the water heats and cools in the pipework. These vessels are supplied pressurised with nitrogen. Through time they lose a bit of that pressure, manifested usually by the system overflow dripping.
The manufacturers recommend re-charging with nitrogen.

That would probably be to reduce oxidation (rusting) of the steel.

 

[Archev]

That would probably be to reduce oxidation (rusting) of the steel.

No the makers spout the same story about atom size. But obviously you’re correct as well.

 

[N2STY]

Yes 100% nitrogen has its benefits but anyone remember the Kwik-Fit up sale it's hard to prove anyway the biggest culprit for tyre pressure change in temperature is moisture

 

[Gadget Geek]

The weakest parts of the tyre for leakage are the contact around the rims and the valve, rather than the atomic structure of the rubber.

 

[AK OK]

The weakest parts of the tyre for leakage are the contact around the rims and the valve, rather than the atomic structure of the rubber.

Don't forget abt nails & screws

 

[toadinapintglass]

Hello, I have only had my car since the end of November. I have topped up the tyre pressures a couple of weeks ago to help with efficiency. I now have a warning at the rear left, 2.3 rather than 2.8 bar. There does not seem to be any form of puncture. Any ideas as to a potential issue? Or is this simply weather related?

Got mine 9th of November.kept lossing the same amount off air as you did but in my rear right tyre. Kwick fix found a small bolt and fixed the tyre

 

[TassieDi]

I've just started getting a low pressure warning in one tyre - the iSmart app tells me it is at 2.3 bar. The manual doesn't tell me what the pressure should normally be. Any advice? [It's OK, I found the label at the driver's door saying the pressure should be 2.8 bar]. Also, the 12V battery is showing as 12.8V (it has recently been replaced) and it normally reads as over 13V.

 

[MSour]

I think mine (MG EV ZS) has the same issue car reads as 2.3bars and continues to say low.. had the same thing and read the panel on the door should be 2.8.. finally those alarm warnings can stop!!

 

[Spinynorman]

I've just started getting a low pressure warning in one tyre - the iSmart app tells me it is at 2.3 bar. The manual doesn't tell me what the pressure should normally be. Any advice? [It's OK, I found the label at the driver's door saying the pressure should be 2.8 bar]. Also, the 12V battery is showing as 12.8V (it has recently been replaced) and it normally reads as over 13V.

On my manual (pdf ZS EV Mk 1/ 20 plate) page 317 gives tyre pressures :-
Tyre Pressure (Cold)
Wheels Unladen
Front Wheels 230kPa/2.3bar/33psi
Rear Wheels 230kPa/2.3bar/33psi
Haven’t checked the door plate though…

mine were 2.3 Bar on delivery, but all four lost pressure in the cold spell we had but subject to Boyles’ law methinks - PV=nrT

 

[Kithmo]

On my manual (pdf ZS EV Mk 1/ 20 plate) page 317 gives tyre pressures :-
Tyre Pressure (Cold)
Wheels Unladen
Front Wheels 230kPa/2.3bar/33psi
Rear Wheels 230kPa/2.3bar/33psi
Haven’t checked the door plate though…

mine were 2.3 Bar on delivery, but all four lost pressure in the cold spell we had but subject to Boyles’ law methinks - PV=nrT

The door plate says the same on mine, 33psi, I usually add a couple of psi (to 35) for economy and it saves tyre wear on the edges.

 

[PaulC82]

Mine seem to fluctuate between 2.7 - 2.9Bar.

 

[Lovemyev]

Mine seem to fluctuate between 2.7 - 2.9Bar.

Same here Paul.
It will vary according to the ambient temperature, I have no concerns regarding this TBH.
Any massive discrepancy in one single tyre should be investigated though.
One day last week, the TPMS was reporting 3.0 Bar on all four tyres.
Later in the evening, the App was reporting a lower reading of around 2.8 Bar.
It can be normal to see one side of the car report a higher reading if parked in direct sun light on a hot day of course.
A low reading on one tyre could indicate a slow puncture of course.
If so, the TPMS will be triggered anyway.
That’s sort of the whole idea of its purpose I guess .

 

[Spinynorman]

The door plate says the same on mine, 33psi, I usually add a couple of psi (to 35) for economy and it saves tyre wear on the edges.

Going over the recommended may give less wear but it also means less tyre in contact with the road surface therefore less traction…

 

[Kithmo]

Going over the recommended may give less wear but it also means less tyre in contact with the road surface therefore less traction…

Not always.
The manufacturer pressures are the "recommended" pressures and can't possibly be always correct to within a couple of psi. Different manufacturer's tyres have different characteristics such as stiffer sidewalls, different materials etc.
I monitor the wear on the tyres on any new car, checking whether the whole tread is in contact with the road by looking at the edge of the tyre. You can see where the tyre is in contact with the road.
If there's no contact evident at the edge then drop the pressure a little, if there is visible signs of contact at the edge then raise the pressures a little until there isn't then drop them. It's technique I've been using for many years and have never suffered uneven wear or grip problems.
Adding 2 psi is hardly going to affect grip much anyway.

 

[Lovemyev]

Not always.
The manufacturer pressures are the "recommended" pressures and can't possibly be always correct to within a couple of psi. Different manufacturer's tyres have different characteristics such as stiffer sidewalls, different materials etc.
I monitor the wear on the tyres on any new car, checking whether the whole tread is in contact with the road by looking at the edge of the tyre. You can see where the tyre is in contact with the road.
If there's no contact evident at the edge then drop the pressure a little, if there is visible signs of contact at the edge then raise the pressures a little until there isn't then drop them. It's technique I've been using for many years and have never suffered uneven wear or grip problems.
Adding 2 psi is hardly going to affect grip much anyway.

After owning a few R/W/D BMW’s in my time, the manufacturers rear tyre pressures are about 2 psi over inflated in my opinion.
Why do I say this, well anybody who has owned one of these cars, will note that the centre section of the tyre, will always wear much faster the outside edges of the tread pattern.
Reduce the tyre pressures by 2 psi on the rears and the tyre will wear more evenly and offer a full 100% contact surface with the road.
The centre tread burns out more quickly, purely because the recommended tyre pressure is a little over inflated IMHO.

 

[Kithmo]

After owning a few R/W/D BMW’s in my time, the manufacturers rear tyre pressures are about 2 psi over inflated in my opinion.
Why do I say this, well anybody who has owned one of these cars, will note that the centre section of the tyre on the rears, will always wear much faster the outside areas of the tread pattern.
The middle of the tyres prematurely wear faster that the outside of the tread.
Reduce the tyre pressures by 2 psi on the rears and the tyre will wear more evenly and offer a full 100% contact surface with the road.
The centre tread burns out more quickly, purely because the recommended tyre pressure is a little over inflated IMHO.

That's the thing with RWD the wear on the rears is accelerated by a slight deviation in the correct (not necessarily manufacturers) pressure and the fronts tend to wear more on the edges due to the car being pushed into the turn rather than driven round it as with FWD.
I'll have to monitor the centre of the tread on the rears of my 4 when I get it next Saturday.

 

[Spinynorman]

Not always.
The manufacturer pressures are the "recommended" pressures and can't possibly be always correct to within a couple of psi. Different manufacturer's tyres have different characteristics such as stiffer sidewalls, different materials etc.
I monitor the wear on the tyres on any new car, checking whether the whole tread is in contact with the road by looking at the edge of the tyre. You can see where the tyre is in contact with the road.
If there's no contact evident at the edge then drop the pressure a little, if there is visible signs of contact at the edge then raise the pressures a little until there isn't then drop them. It's technique I've been using for many years and have never suffered uneven wear or grip problems.
Adding 2 psi is hardly going to affect grip much anyway.

Interesting. Didn’t know that - just assumed they did the work on the optimum values when obviously they don’t - or at the very least, don’t customise for each model. Will do as you’ve recommended and monitor the tread wear in future. TYVM.

 

[TassieDi]

As well as new info from all we early adopters, I'm learning heaps about cars in general on this forum. Thankyou to you all for sharing what you know.