Unstable car over 65mph

[nm36]

Hi All,

I recently got an MG M4 SE Long Range (66kw), which I have used predominantly for very short trips at low speed and I have been generally quite happy with it.

However, over Easter, I went for a road trip in the countryside, and I noticed the car felt quite unstable every time I was going faster than 70mph. The feeling was the same as when there is strong wind, with the car moving left and right randomly... the problem is there was absolutely no wind. It is definitely not the lane assistance, as that would beep and turn the car back to the centre, whereas in my case it was some sort of illogical zig-zag.

For additional context, we were 4 in the car, with a couple of bags in the trunk. Tires pressure was 2.5bar on the front wheels and 2.6 on the rear ones. I know this might be slightly low for a fully loaded car but should still be within the parameters? My previous car was an Alfa Romeo Giulietta, which is a similar size, and I never felt this unless with strong wind, and definitely I was not used to adjust the tyre pressure depending on the number of people

Any clue on potential reasons? or is this normal for a car like this one?

 

[webhiker]

That sounds odd. I have during Easter in my MG4 Trophy Extended range done 3000km and tested it at 189km/h with no wobbling or the like.
Being a non-tech I can only say that does not sound right.

 

[nm36]

What's your tyre pressure?

 

[webhiker]

What's your tyre pressure?

2.6, 1 person and a light cargo. I did not check tyre pressure while driving, but it usually heats up to about 2.8

 

[Buster72]

Can't be of any help unfortunately because I have never experienced anything like that.
A few months ago we were coming back on the M4 and the wind was as very high and rain was torrential.
And the car SE SR was perfectly steady and stable.

 

[Kithmo]

I would put at least 2.8 bar pressure in the rear tyres for a fully loaded car.
(It actually states that pressure for a fully laden car on the last page of the manual and on the door sticker)

 

[Matt x power]

I presume you have switched off lane keep assist?

 

[nm36]

thanks all - can it really be the rear tyre pressure? 2.6 might be slightly low... but really that low to make drive at speed uncomfortable to say the least? I also had a few instances of aquaplaning/hydroplaning during the weekend, which seemed excessive for the amount of water on the ground.. and I am wondering if that could be also related.

It is 100% not the lane keep assistance as that will cause the car to beep and steer abruptly whereas this is more zig-zag when at speed.. exactly as when there is strong wind outside...

 

[Matt x power]

My steers so much better with lka off especially in the dead ahead position at speed

 

[Flightengineer]

thanks all - can it really be the rear tyre pressure?

I felt vibration on the steering wheel in the same conditions. Maybe my vibration and your instablity have the same cause?
My dealer replaced tyres followed by front wheel adjustment, and those actions solved the problem.

 

[fnegroni]

it might be that you are sensitive to the stock tyres which are most likely using the Chinese compounds (whether Bridgestone or Continental)
I changed mines to European compound Bridgestone Turanza 6 and the car at 70mph is rock solid now, while previously anything above 60mph felt like floating

 

[kc1966]

Rock solid no play, wobble. Tested at the weekend 700km 4 adults and luggage.

 

[Rolfe]

My tyres are a bit low at the moment and this is not happening to me.

 

[Ian Key]

@nm36 Might be worth getting the tracking checked.

If the tyre fitters say they don't have the values for the MG4 they are on page 322 of the owner's manual.

 

[JonnyG]

thanks all - can it really be the rear tyre pressure?

It could be the tyres themselves ... what brand have you got and what mileage are you at ?

There have been reports on here of OEM tyres having to be replaced due to issues, but I think these were generally EU cars.

 

[Flightengineer]

It could be the tyres themselves ... what brand have you got and what mileage are you at ?

Original tyres were "made in China Bridgestone". Dealer replaced by Kreber made in Romania. I think the fault comes from wrong storage of car.

 

[fnegroni]

Original tyres were "made in China Bridgestone". Dealer replaced by Kreber made in Romania. I think the fault comes from wrong storage of car.

Wrong storage?

 

[siteguru]

Maybe underinflated during shipping etc. and so created excessive flat spots?

 

[mg4mc]

I mean my summer car sits on its tyres for months at a time over winter, yes when I drive it after that it has flat spots, but they are gone within a few miles. I can't image being on a ship for what 30/40 days(?) would cause such issues (ref XPower thread as well).

 

[jamherber]

I think it's possible that it's a contributory factor. Our new x-power purchased last week was manufactured in September, arrived late October to the UK and then presumably sat around somewhere until we bought it 5 months later.