[bmhewett]

well, its been 5 years since i got my G30 from dealer in 2018, from factory my car has 245/40/19 and 275/35/19 tyres and sport suspension .during those years i have replaced tires many, many times, the problem is the tyre profile, is too slim so in any bump or pot hole, the tyre breaks, so i decided to go with a larger size this time, i just ordered 245/45 r19 front, 275/40 r19 rear tyres, i see 'ill be the only one in this forum with this configuration so i´d aprecciate any advice. i'll go from 26.72 inches to 27.68 inches of diameter... less than an inch , later i'll show pics. thanks

[cna90]

Originally Posted by bmhewett

well, its been 5 years since i got my G30 from dealer in 2018, from factory my car has 245/40/19 and 275/35/19 tyres and sport suspension .during those years i have replaced tires many, many times, the problem is the tyre profile, is too slim so in any bump or pot hole, the tyre breaks, so i decided to go with a larger size this time, i just ordered 245/45 r19 front, 275/40 r19 rear tyres, i see 'ill be the only one in this forum with this configuration so i´d aprecciate any advice. i'll go from 26.72 inches to 27.68 inches of diameter... less than an inch , later i'll show pics. thanks

I am running 245/40R20 front and 275/35/20 rear for a little while now (7 series sizes). No problem at all. I know a lot of people in the forum are doing this on their 5er xDrive with no problem as well.
Which is 27.7” front and 27.6 rear with rear %0.4 smaller than the fronts in diameter. My front and rear difference is similar to what 19”OE is; like what you originally had on the car. I have set my idrive tire selection to 275/35/19 hoping the transfer case software matches the size difference.

With what you’re planning on running, it’ll effectively be an square setup as front and rear will be the same diameters while wider in size in the rear.
Although I don’t have this setup, I believe that’s 19” setup for 7 series that has the same transfer case as our cars. I would select the square tire setup in iDrive tire menu and call it a day.

I’d recommend switching to regular tires over run flats. They have less issues and much more comfortable ride quality. Also much cheaper.
The problem are mainly the rims. 8” wide rim is not wide enough for 245 (9” for 275), which make the side wall bulge and more prone to separating rubber from metal on the RFT side wall.

I switched to 7 series rim which is 8.5” wide in front and 10” wide in rear to make room for the width of the tires.

[bmhewett]

thank you for your comments , ill post some pics soon. regards

[bmhewett]

[bmhewett]

so the final veredict;

the improvement is huge, the new tyres barely fit in the wheel arch, bigger impossible..

i took my car to high speed road and i felt very good respond and handling, now i feel like going over a cloud, really, it feels like 7 series the new tyres absorb all the inperfections of the surface. cornering is not as sharp as before but really for me is ok, i highly recommend

[lanlilan]

Do you notice any change in road or tire noise?

[WretchedRefuse]

Also have you been able to compare your speedometer with true GPS speed? I expect they should be very close now.

[gasoline]

Originally Posted by bmhewett

so the final veredict;

the improvement is huge, the new tyres barely fit in the wheel arch, bigger impossible..

i took my car to high speed road and i felt very good respond and handling, now i feel like going over a cloud, really, it feels like 7 series the new tyres absorb all the inperfections of the surface. cornering is not as sharp as before but really for me is ok, i highly recommend

Hi,
I am intending to replace my stock tyres with the same size as you did.
-You say it barely fits and not sharp cornering, do you feel any friction when cornering in the wheel arch?
- Any change in road noise?
Thx

[emre]

Originally Posted by WretchedRefuse

Also have you been able to compare your speedometer with true GPS speed? I expect they should be very close now.

I went from oem sizes to 245/40/20 & 275/35/20
Speedometer and GPS speed match now.

[Magnit]

Originally Posted by emre

I went from oem sizes to 245/40/20 & 275/35/20
Speedometer and GPS speed match now.

How different is handling and acceleration? Any notable changes?

[emre]

Originally Posted by Magnit

How different is handling and acceleration? Any notable changes?

slight increase in body roll when cornering hard, nothing dramatic.
acceleration must be slower but I do not feel it.