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BMW 5-Series (G30) Forum 2017+ BMW 5 Series (G30) General Discussions Please help - ET/rims confirmation

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      02-21-2020, 08:41 AM   #1
luke1990
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Please help - ET/rims confirmation

Hi guys,

I'm buying new forged rims and need and advice on size + ET. Already posted in the tire/suspension/wheel forum, however no reply. Forged rims are expensive so I just want to get a confirmation ideally that I'm not doing a blunder before I take the plunge. THANKS A TON!

I have 540ix G30 and I will go 19s (lighter, good for handling, we have bad roads ) and put 255/295 tires on it (+10mm front, +20mm back; already checked - overall size is good). I'm thinking 19/8,5 ET25 front and 19/10 ET41 back. Its basically the same setup as OEM 20s.

1. Is the offset OK? I've seen some people run ET36 back on 10s . Its like putting 12mm spacers front/back. Or with 36 and 20mm back, but then back is 8mm more out than front. I aim for best handling and no rub .
2. Is 8,5 enough for 255s and 10 for 295s? Or go 0,5 more on each? For handling/sporty driving. This smaller concave or this wider flat? I think 8,5/10 is enough and it will be a bit lighter, but I've noticed sports/M cars have rather flat vs concave and dont know why.

Please save me! THANKS A TON!
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      02-21-2020, 09:04 AM   #2
PetieD 7
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Quote:
Originally Posted by luke1990 View Post
Hi guys,

I'm buying new forged rims and need and advice on size + ET. Already posted in the tire/suspension/wheel forum, however no reply. Forged rims are expensive so I just want to get a confirmation ideally that I'm not doing a blunder before I take the plunge. THANKS A TON!

I have 540ix G30 and I will go 19s (lighter, good for handling, we have bad roads ) and put 255/295 tires on it (+10mm front, +20mm back; already checked - overall size is good). I'm thinking 19/8,5 ET25 front and 19/10 ET41 back. Its basically the same setup as OEM 20s.

1. Is the offset OK? I've seen some people run ET36 back on 10s . Its like putting 12mm spacers front/back. Or with 36 and 20mm back, but then back is 8mm more out than front. I aim for best handling and no rub .
2. Is 8,5 enough for 255s and 10 for 295s? Or go 0,5 more on each? For handling/sporty driving. This smaller concave or this wider flat? I think 8,5/10 is enough and it will be a bit lighter, but I've noticed sports/M cars have rather flat vs concave and dont know why.

Please save me! THANKS A TON!
FYI / Reference only...

Recently, purchased a new set of wheels (semi-forged), and tires (staggered setup) for my 540i xDrive M Sport. Here is the following info regarding my setup:

Wheels:
Front: 20x9 ET 30
Rear: 20x10 ET 42

Tires:
From: 255/35/20
Rear: 285/30/2

IMHO...this is a conservative setup!
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      02-21-2020, 09:34 AM   #3
luke1990
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Quote:
Originally Posted by PetieD 7 View Post
FYI / Reference only...

Recently, purchased a new set of wheels (semi-forged), and tires (staggered setup) for my 540i xDrive M Sport. Here is the following info regarding my setup:

Wheels:
Front: 20x9 ET 30
Rear: 20x10 ET 42

Tires:
From: 255/35/20
Rear: 285/30/2

IMHO...this is a conservative setup!
Thanks! And all good? No rubbing? Happy with how far the wheels are out?

And what do you mean conservative setup? I mean you could put 295s back and would fit even better -> you now have slightly larger fronts than back . Or something else?
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      02-21-2020, 10:33 AM   #4
PetieD 7
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Quote:
Originally Posted by luke1990 View Post
Quote:
Originally Posted by PetieD 7 View Post
FYI / Reference only...

Recently, purchased a new set of wheels (semi-forged), and tires (staggered setup) for my 540i xDrive M Sport. Here is the following info regarding my setup:

Wheels:
Front: 20x9 ET 30
Rear: 20x10 ET 42

Tires:
From: 255/35/20
Rear: 285/30/2

IMHO...this is a conservative setup!
Thanks! And all good? No rubbing? Happy with how far the wheels are out?

And what do you mean conservative setup? I mean you could put 295s back and would fit even better -> you now have slightly larger fronts than back . Or something else?
Yes, no rubbing...I'm cool with my setup. IMHO, the overall fitment has that 99.9% flushed (stance) looks to it...not too aggressive.

I was advised to go with either 245 (OEM) or 255 size for the front, and recommended with 285 for the rear. Although, from this forum I've noticed 295 and 305 were used for the rear.

As well, my car came with OEM 20" staggered with xDrive option. Therefore, I selected these sizes (255/35 & 285/30) which kept the overall diameter as close as possible with the OEM setup in order to avoid problem(s)/issue(s)/damage(s) to the all-wheel drivetrain/system down-the-lane.
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      02-22-2020, 01:30 PM   #5
luke1990
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Quote:
Originally Posted by PetieD 7 View Post
Yes, no rubbing...I'm cool with my setup. IMHO, the overall fitment has that 99.9% flushed (stance) looks to it...not too aggressive.

I was advised to go with either 245 (OEM) or 255 size for the front, and recommended with 285 for the rear. Although, from this forum I've noticed 295 and 305 were used for the rear.

As well, my car came with OEM 20" staggered with xDrive option. Therefore, I selected these sizes (255/35 & 285/30) which kept the overall diameter as close as possible with the OEM setup in order to avoid problem(s)/issue(s)/damage(s) to the all-wheel drivetrain/system down-the-lane.
good! Reason why Im leaning towards 295s is that they are actually closer to the diameter of 255s in front than 285s. On 19s - 245/275 is -1,75mm in tire circumverence for the rear while 255/285 is -2,25mm. 255/295 is +1,25mm so yeah oposite of what stock is, but closer in size by 1mm. Plus I figured if you're not going staggered, you have 0 difference, so the xdrive must be tuned for that as well .

Btw on 20s 255/285 are -3,75mm smaller in rear - this is a good website to check that; thats a lot I think. If you go 255/295 you're +0,75mm only
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      02-23-2020, 10:03 AM   #6
PetieD 7
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Quote:
Originally Posted by luke1990 View Post
Quote:
Originally Posted by PetieD 7 View Post
Yes, no rubbing...I'm cool with my setup. IMHO, the overall fitment has that 99.9% flushed (stance) looks to it...not too aggressive.

I was advised to go with either 245 (OEM) or 255 size for the front, and recommended with 285 for the rear. Although, from this forum I've noticed 295 and 305 were used for the rear.

As well, my car came with OEM 20" staggered with xDrive option. Therefore, I selected these sizes (255/35 & 285/30) which kept the overall diameter as close as possible with the OEM setup in order to avoid problem(s)/issue(s)/damage(s) to the all-wheel drivetrain/system down-the-lane.
good! Reason why Im leaning towards 295s is that they are actually closer to the diameter of 255s in front than 285s. On 19s - 245/275 is -1,75mm in tire circumverence for the rear while 255/285 is -2,25mm. 255/295 is +1,25mm so yeah oposite of what stock is, but closer in size by 1mm. Plus I figured if you're not going staggered, you have 0 difference, so the xdrive must be tuned for that as well .

Btw on 20s 255/285 are -3,75mm smaller in rear - this is a good website to check that; thats a lot I think. If you go 255/295 you're +0,75mm only
The comparisons should be:

Front 245/35 (current) vs. 255/35 (new), and,
Rear 275/30 (current) vs. 285/30 (new).

The website provided was based on current and new for "squared" setup, not "per axle". For example (i.e. staggered) "current" front setup (245/35), and the "new" front setup (255/35). This would be the same calculations for rear "new/current" setup (I.e. 275/30 vs 285/30). That said, two calculations needed for staggered setup. And, the squared would need only one calculation.
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