[estorilbluef36]

i have a 2018 440 GC and i want to ditch run flats for MPS4S. however i do not know the best size for the tires. on tire rack i put in my car and it said 225 40 19 for front and 255 35 19 for the rear. is this good or what sizes should i get?

[jh_f30]

Originally Posted by estorilbluef36

i have a 2018 440 GC and i want to ditch run flats for MPS4S. however i do not know the best size for the tires. on tire rack i put in my car and it said 225 40 19 for front and 255 35 19 for the rear. is this good or what sizes should i get?

Why not just match the sizes that are currently on the car?

[estorilbluef36]

Originally Posted by jh_f30

Why not just match the sizes that are currently on the car?

i don't know. that's why i'm asking

[jh_f30]

Originally Posted by estorilbluef36

i don't know. that's why i'm asking

Those are the stock sizes so they'll be what BMW recommends. As far as what's "best", that might be up for debate. Depends on what you want. If you're fine with the stock setup, keep the stock sizes. If you wanna go a little wider up front, use this:
https://tiresize.com/calculator/

Just make sure you know the wheel widths, which I think are 19x8" front, 19x8.5" rear, and make sure whatever size tires you go with will fit. (ie. probably shouldn't go more than 245 on the fronts). That said, 255s are probably about as wide as you should go on 8.5" wide rear wheels.

[alohasurftoad]

255 is max width on 8.5" rear, so leave it.

increasing the front size to 245/35/19 will reduce some turn-in sharpness, especially when compared to a narrower 225 stiff sidewalled runflat.

for me, the benefit of reduced understeer and overall grip up front with a 245 would outweigh the 225 sharper turn in. others prefer sharp turn in over the extra grip up front. so you have to decide what type of handling you desire.

here is a member that changed from 225/40 to 245/35 on a F30. rear is 255

[.BMW.]

I agree.

245 front and 255 rear is a nice setup.