MG4 X Power Tyre Upgrade

[tsedge]

Judging from all accounts, i.e. our mutual attempts at elimination by tyre replacement and rebalancing, even so - called extra 'fine' balancing which I elected for on fitting ( mine from Formula 1 Autocentre.co.uk ), it's NOT the tyres !!

As a matter of interest, do the MG models without the rear roof spoiler have the vibration problem ?

It hasn't shown up with Trophy owners who have the spoiler, so it doesn't seem like that has anything to do with it.

We have be grasping in the dark for many months without finding an answer so I am pretty sure there isn't an obvious cause to find, hence why it is plausible that it is something weird with the right rear driveshaft as is rumoured.

People have speculated about pretty much all the unsprung mass on the car including wobbly discs. The biggest mystery has been why only some people report it.

 

[GlobalHealer69]

It hasn't shown up with Trophy owners who have the spoiler, so it doesn't seem like that has anything to do with it.

We have be grasping in the dark for many months without finding an answer so I am pretty sure there isn't an obvious cause to find, hence why it is plausible that it is something weird with the right rear driveshaft as is rumoured.

People have speculated about pretty much all the unsprung mass on the car including wobbly discs. The biggest mystery has been why only some people report it.

I have the Trophy ( as I stated it's an EX ).

 

[tsedge]

I have the Trophy ( as I stated it's an EX ).

Ok, but there absolutely no mass reports about this with Trophys. Issues with an individual car can be down to all sorts of things.

 

[GlobalHealer69]

Ok, but there absolutely no mass reports about this with Trophys. Issues with an individual car can be down to all sorts of things.

Perhaps there aren't as many on the road compared to much cheaper models.

 

[tsedge]

Perhaps there aren't as many on the road compared to much cheaper models.

There are loads of Trophys around, it is very popular.

 

[siteguru]

Just not the Trophy ER model ... not as many of them.

 

[tsedge]

Just not the Trophy ER model ... not as many of them.

Yes but the point remains that there are an awful lot of cars with the roof spoilers that don't have this issue so it is highly unlikely it is related to that.

 

[Fogey]

Yes but the point remains that there are an awful lot of cars with the roof spoilers that don't have this issue so it is highly unlikely it is related to that.

Especially as the vibration has been measured as being 3x the roadwheel rotational speed. Unless there are 2 separate sources, and 2 different vibrations...

 

[ilukey77]

If you want more grip just change your tyres to a more performance oriented rubber.

The day I lost the back end was the day I decided to ditch the stock rubber.

I've since done 7000 miles on my PS5's and lack of grip has not been an issue since. (No matter how spirited or how wet it's been.)

Go up a size if you wish, especially if you're tracking it, but even on decent 235's, you won't get near the full capabilities of the tyre on the road.

(Unless you drive like a lunatic ?)

View attachment 30383

Ohh I’ve been known to drive somewhat lunatic ish ?..

I know the pilot sport 5s are going to be much better just wondering if the added inch all round will give it a little better grip and if it can or has been done without issues..

Dealer/ service manager said he will lower my car for me so supper happy about that and cheaper than suspension place quoted ..
But suggested that like you are going to do bricktop is get the vibe fixed first then think about lowering.

Which even with having the springs and now hanging to get them fitted I’m going to wait!

it is the better option not so much for warranty as he explained we have taken pictures of the car in standard form ..
we are aware/MG is aware a fix is incoming so lowering is not really going to effect warranty's so much as it’s more to not complicate the fix .

But like I said just thinking if I could slap 245s all round without any tyre rubbing
(Fronts maybe might be a issue with 30mm lowering)
(rears should be good even with the 30mm drop)
It would help with grip no doubt

 

[Muffler]

Some useful info on tyre sizes here 235/45R18 Tires

The 245's certainly look ok with stock rims with only very minor error in speed reading (assuming speedo overstates speed like every other car - may even improve accuracy). Still looking at tyre options myself... ?

 

[siteguru]

FWIW the speedo in my MG4 is pretty much dead on accurate vs GPS speed tracking. Anything that made it read lower than actual would make the car illegal (if stopped and checked).

 

[Muffler]

FWIW the speedo in my MG4 is pretty much dead on accurate vs GPS speed tracking. Anything that made it read lower than actual would make the car illegal (if stopped and checked).

Interesting! Practically everything I've driven in recent years has almost without fail, when checked against GPS, shown circa -1mph at 30, -2mph at 50 and -3mph at 70
Agree though, wouldn't make that call without doing a GPS check first ?

 

[ilukey77]

FWIW the speedo in my MG4 is pretty much dead on accurate vs GPS speed tracking. Anything that made it read lower than actual would make the car illegal (if stopped and checked).

Not sure what the rules are in the uk but to my understanding in AUS your allowed change within 5% of height difference so 245s on the 8 inch wide rim is acceptable because going wider reduces the rolling diameter so the speedo will show 1-2km/h lower than normal..
And to be honest that’s b kinda a win win because the 235/45:18s are more expensive than the 245/45 18s here and realistically i used to drive a 2007 Honda jazz as a company car and it was easily 10km/h out so at 110km/h the gps was saying 98/100km stock rims and tyres so by default the car was out by a bit!!

So I can’t see a problem

 

[mGizmo]

... you won't get near the full capabilities of the tyre on the road.

(Unless you drive like a lunatic ?)

Challenge accepted!

 

[siteguru]

Interesting! Practically everything I've driven in recent years has almost without fail, when checked against GPS, shown circa -1mph at 30, -2mph at 50 and -3mph at 70
Agree though, wouldn't make that call without doing a GPS check first ?

Every previous car I've had has over-read ... and the standards allow for this: the speedo must not read a speed lower than actual, but may over-read by up to 10% (I think). My previous Golf GT and Insignia both read 75 on the speedo when GPS said 70, but my MG4 aligns almost exactly. So if a change increased the rolling diameter of the tyres then the car would travel a further distance than what the speedo was calibrated for, hence the speed would be higher than expected - thus in my case the speedo would end up under-reading.

Per the chart in post #132 the 45 profile tyres have a 0.4" increase in rolling diameter. Therefore the speedo may under-read by 1.5%, so at an indicated 70 you'd be doing an actual 71.05 - the chances of being pulled, checked and found are minimal ... and once the tyres had worn a couple of mm the calibration would likely become correct.

 

[JonnyG]

I use TomTom and Waze a lot and my speedo is almost spot on with their GPS speeds as well at high speeds (70mph) ?

Seems like MG can get the speedo dead accurate but the inside temperature way out ?

 

[Muffler]

I use TomTom and Waze a lot and my speedo is almost spot on with their GPS speeds as well at high speeds (70mph) ?

Seems like MG can get the speedo dead accurate but the inside temperature way out ?

Checked mine yesterday against phone/TomTom GPS and looked to be about 1mph out at circa 60-70 which I must admit is the most accurate I've ever experienced. It also means that swapping out the 235/45R18 rubber for 245/45R18 won't be a problem for me so now booked in on Friday for a set of Goodyear Vector 4Seasons Gen 3 to be fitted ?
- Set of stock tyres with <200miles use available for sale soon after... ?

 

[Muffler]

245/45R18 GY Vector 4S G3 tyres now fitted - impressive grip and speedo matches GPS exactly ?

 

[fnegroni]

245/45R18 GY Vector 4S G3 tyres now fitted - impressive grip and speedo matches GPS exactly ?

That size is what the car should have come with from day 1.

Lighter less powerful cars have had tyres bigger than this fitted from stock.

 

[powerfulx]

Not sure what the rules are in the uk but to my understanding in AUS your allowed change within 5% of height difference so 245s on the 8 inch wide rim is acceptable because going wider reduces the rolling diameter so the speedo will show 1-2km/h lower than normal..
And to be honest that’s b kinda a win win because the 235/45:18s are more expensive than the 245/45 18s here and realistically i used to drive a 2007 Honda jazz as a company car and it was easily 10km/h out so at 110km/h the gps was saying 98/100km stock rims and tyres so by default the car was out by a bit!!

So I can’t see a problem

Yep , i looked at this too, 245s no problem, however in the past ive worked out trying a performance tyre can be enough.