[Nate0m]

I just purchased a 2015 335i GT.

The car came equipped with 225/50R18. I am looking to upgrade to 225/45R19, 235/40-45R19, ro 245/40R19. Any suggestions?

I am also looking at the possibility of an engine tune. Has anyone done this? What route did you take?

Thanks,

[GoSpursGo]

Congrats! Now where are the pics???

I have 19” on my GT but I think they look too small....go 20” at least!

[Billfitz]

So there are no potholes in Detroit?

[Nate0m]

Originally Posted by Billfitz

So there are no potholes in Detroit?

Of course there are. That's why i'm looking at 19" rather than 20".

[Billfitz]

If you're going with 19'' you'd best be sure to have wheel and tire insurance and no RFTs.

[Sportstick]

Going from 18" to 19" is not an upgrade. It is only larger and heavier, for those who see a .5" increase in diameter on each side. Ride quality, tire cost, acceleration, braking distance, and frequency of repairing/replacing dented rims will deteriorate...from one Detroiter (OK, Oakland County) to another. So,you're upsizing, but in several ways, downgrading. As my prior colleagues at one of the Big 3 used to say, "Designers love big wheels. Engineers don't."

[Nate0m]

Didn't realize i was asking for an education on the quality of my local roads. I am looking to "upgrade" the aesthetics. less side wall will also improve the handling. Just looking for a nice looking summer set up.

[Sportstick]

Originally Posted by Nate0m

Didn't realize i was asking for an education on the quality of my local roads. I am looking to "upgrade" the aesthetics. less side wall will also improve the handling. Just looking for a nice looking summer set up.

Not so much an education on our roads as some experience on the greater "cons" than "pros" of the basic idea of larger wheels...a styling fad with negative overall dynamic results. The downside of a heavier rotating mass also applies on smooth roads. Everything is a compromise. When you apply this particular aesthetic change, you at least trade off accel/braking performance, fuel economy, even on the best surface. Yours to decide as long as you have all the info...

BTW, most of the issue with GT handling has to do with the height of the vehicle's roll center, as well as suspension calibration. The shorter sidewall will add a touch of "crispness" to initial steering response, but it's still a relatively tall and heavy load to change direction...3" taller than non-GT 3 Series.

You could probably improve steering response more by swapping out the lower control arms from M3/M4 for +1 degree of negative camber, if they happen to be compatible with XDrive...I'm not sure. The LCA swap had an outstanding effect on my 6MT/TrackPack-2 Series, where I removed the 18s and installed 17s with great result from a dynamics point of view.

[Billfitz]

Originally Posted by Nate0m

less side wall will also improve the handling.

If that were true the rim size for Formula 1 wouldn't be 13 inches. One of the reasons why is to give better performance with the very stiff suspensions of F1. Another is to minimize the possibility of impact damage to the wheel, tire and car. Big rims with small tires look nice, but at the cost of performance and durability.

[Sportstick]

Originally Posted by Billfitz

Big rims with small tires look nice, but at the cost of performance and durability.

You think so? I see them and just think there's someone else who fell for the fashion-of-the-moment, as they are completely free to do! Reminds me of when women thought they had to give themselves make-up black eyes ("smoky"?) because it was the current fad... designed no doubt to sell more cosmetics, just as this trend stimulates sales for wheel manufacturers. Watch...once enough large wheels have penetrated the market, someone will start a fad to return to smaller wheels, and then those will "look good" again...

[Billfitz]

I think they look good to a point, though when I see 21" rims with 30 aspect ratio tires, usually on ricers, all I can do is laugh at how silly they are.

[Nate0m]

Originally Posted by GoSpursGo

Congrats! Now where are the pics???

I have 19” on my GT but I think they look too small....go 20” at least!

What size tires did you go with for your 19's? Did you stick with run flats?

[GoSpursGo]

Not sure of the specs but they’re runflats that came with our car.

[lethbridge]

I think 19" are fine on the GT (dependent on the condition of the roads) mine are the standard BMW option of staggered 225/45/19, 255/40/19. I keep with run flats and don't find them an issue at all apart from the cost as they are an unusual size (in run flats at least). Note as an xDrive I don't have MSport springs and I have adaptive suspension. Look at it this way the GT wheels are a size bigger than the sedan (so 19s on GT are the equivalent of 18" wheels on the sedan) - over here I don't hear any complaints at that size or indeed 19" on the sedan which are a standard option that many go for (certainly most on our very active forum). 20" on the sedan & 21" on the GT is where I think you would hit the real issues as we saw with the old 3 series when M Sports were running on 19" but that was 255/35 rubber as the wheels were smaller again. I'm speaking from a UK road perspective (though far from perfect).