[kromix]

So I'm trying to get proper fitment and be as close to spec as possible.

340i - 400M 18" wheels

going with a staggered 19" setup.

Wheels are:

19x9 ET+35
19x10.5 ET+45

Tires I am not sure, I was recommeneded 245/35 and 275/35.

When I plug those numbers into a wheel/tire calculator the fronts seem to be good @ -.86% diff, where as the rear is @ -2.06%... Is there a better tire size setup that will be closer to spec? I tried playing with the numbers myself but didn't get a better result....

Front

Rear


Thoughts?

[snj49er]

If you compare the new front and rear diameters, they're 3% off. (675/654) If you drop down to 275/30 on the rear, they'll be within 1%. 285/30 is even closer to the diameter of 245/35, but that may cause clearance issues.

[kromix]

You are right, so based on the calculator the proper fitment would be 245/35/19 and 285/30/19 right? Based on the numbers I see that looks "proper" or closest to spec, why do some people say 275/30 in the rear is the right size when its further away in number? What am I missing?



or do I go with 265/35? ahhh I'm not sure what would be the proper size anymore....

[snj49er]

Originally Posted by kromix

You are right, so based on the calculator the proper fitment would be 245/35/19 and 285/30/19 right? Based on the numbers I see that looks "proper" or closest to spec, why do some people say 275/30 in the rear is the right size when its further away in number? What am I missing?

You'll see a lot of 245/275 and 235/265 combinations on the forum. I think most people will tell you that 285 will rub in the rear without question but some guys seem to have gotten it to work. It will depend on your suspension and the shape of the tire that you select. I'd stick with 275 unless you're into problem solving.

http://f30.bimmerpost.com/forums/sho...light=285%2F30

[kromix]

Originally Posted by snj49er

You'll see a lot of 245/275 and 235/265 combinations on the forum. I think most people will tell you that 285 will rub in the rear without question but some guys seem to have gotten it to work. It will depend on your suspension and the shape of the tire that you select. I'd stick with 275 unless you're into problem solving.

http://f30.bimmerpost.com/forums/sho...light=285%2F30

So wouldn't the closest to OEM spec or "proper" fitment then be 245/35/19 and 265/35/19 ??

[snj49er]

Originally Posted by kromix

So wouldn't the closest to OEM spec or "proper" fitment then be 245/35/19 and 265/35/19 ??

The OEM F30 staggered tires are 225/40-19 and 255/35-19. On F10's, the OEM staggered setup is 245/40-19 and 275/35-19. Both of these are also used on xdrive models where the F/R diameters must be kept close. Not sure what makes you say that that 245/35 - 265/35 is more proper.

Typically, when the rear tire is 30 mm or so wider, you'll want to reduce its profile to keep the diameter close to the fronts. If it's not clear to you...increasing the tire's width also increases its diameter since the profile is expressed as a percentage of the width. So going from a 245/35 to a 265/35 will cause the diameter to increase by nearly a half inch. If that is clear, forget I mentioned it.

[kromix]

Well it's somewhat clear(I'm no expert), but I guess what I am saying is, using the calculator, the numbers tell me the closest to OEM diameter to stocks would be 245/35 and 265/35.....

I get to this because these calculators show the closest numbers to eachother and to the original wheels size.... (Unless I am comparing the wrong parameters)

I have bolded the closest to OEM of each parameter, so thats why I think the "most proper" would be 245/35 and 265/35? Or is my logic flawed somewhere

OEM Front 18 in: 659.7mm
OEM Front 19 in: 662.6mm
245/35 Diameter: 654.1mm
235/40 Diameter: 670.6mm

OEM Front 18 in Circ: 2072.5mm
OEM Front 19 in Circ: 2081.6mm
245/35 Circumference: 2054.9mm
235/40 Circumference: 2106.8mm



OEM Rear 18 in: 661.2mm
OEM Rear 19 in: 661.1mm
265/35 Diameter: 668.1mm
275/35 Diameter: 675.1mm

OEM Rear 18 in Circu: 2077.2mm
OEM Rear 19 in Circu: 2076.9mm
265/35 Circumference: 2098.9mm
275/35 Circumference: 2120.9mm

[snj49er]

Oh, I see where you're going. Forget about comparing the diameters of the OEM front tires to the new ones...you'll want to compare the size of the new fronts to the new rears. 245/35 has a diameter within 1% of 275/30 and 235/35 is within .85% of 265/30.

[kromix]

Oh ok so you are saying that when buying tires you are worried about front and rears matching and not how close the original to the new ones are?

[snj49er]

Originally Posted by kromix

Oh ok so you are saying that when buying tires you are worried about front and rears matching and not how close the original to the new ones are?

Right, within limits. The OEM tires are 26" in diameter +/-. You can probably go up to 3/4" larger without running into problems but you'll want to keep the fronts and rears reasonably close...within 1% if you have xdrive.

Decide what your goals are. If you want to minimize wheel damage with bad road conditions, you might want to consider a +1 or +2 setup. I.e., a 235/40 or 245/40 front provides a 4mm or 8mm larger sidewall than the OEM 225/40. 245/35 has a 4mm smaller sidewall and 235/35 is almost 8mm smaller. The smaller sidewalls look cool, but they'll leave the wheels more susceptible to damage. The smaller tires will increase your wheel gap, so they're probably not a great choice for cars that already have a large gap.

There's been a boatload of discussion here on tire fitment. Look at a lot of pictures and read some of the threads.

[kromix]

Originally Posted by snj49er

Right, within limits. The OEM tires are 26" in diameter +/-. You can probably go up to 3/4" larger without running into problems but you'll want to keep the fronts and rears reasonably close...within 1% if you have xdrive.

Decide what your goals are. If you want to minimize wheel damage with bad road conditions, you might want to consider a +1 or +2 setup. I.e., a 235/40 or 245/40 front provides a 4mm or 8mm larger sidewall than the OEM 225/40. 245/35 has a 4mm smaller sidewall and 235/35 is almost 8mm smaller. The smaller sidewalls look cool, but they'll leave the wheels more susceptible to damage. The smaller tires will increase your wheel gap, so they're probably not a great choice for cars that already have a large gap.

There's been a boatload of discussion here on tire fitment. Look at a lot of pictures and read some of the threads.

Thanks! Yea the sidewall protection is not as important to me in flat no-snow florida as it is to you in NJ i'm sure....

245/35 in the front for sure, so in your opinion I should then go 275/35 rear right?

[.BMW.]

Since your car is RWD (not xDrive) you dont have to match front and rear diameters.

Your own proposal with 245/35-19 front and 265/35-19 rear will fit fine.

If you however would like to match front and rear diameters and also match your new wheel widths a bit better (equal amount of tire stretch on front and rear) I would recommend 235 front and 275 rear (both tire and wheel widths differs by about 1.5" front to rear).

F: 9x19" ET35, 235/35-19 (2% shorter than OEM)
R: 10.5x19" ET45, 275/30-19 (2% shorter than OEM)

or

F: 9x19" ET35, 235/40-19 (2% taller than OEM)
R: 10.5x19" ET45, 275/35-19 (2% taller than OEM)

[kromix]

Originally Posted by .BMW.

Since your car is RWD (not xDrive) you dont have to match front and rear diameters.

Your own proposal with 245/35-19 front and 265/35-19 rear will fit fine.

If you however would like to match front and rear diameters and also match your new wheel widths a bit better (equal amount of tire stretch on front and rear) I would recommend 235 front and 275 rear (both tire and wheel widths differs by about 1.5" front to rear).

F: 9x19" ET35, 235/35-19 (2% shorter than OEM)
R: 10.5x19" ET45, 275/30-19 (2% shorter than OEM)

or

F: 9x19" ET35, 235/40-19 (2% taller than OEM)
R: 10.5x19" ET45, 275/35-19 (2% taller than OEM)

Sounds like the larger sidewalls in the 40 and 35 profile would be a better choice right? More rim protection & less wheel gap? Anything else I should know about this setup? rubbing etc? Leaning towards this now...

F: 9x19" ET35, 235/40-19 (2% taller than OEM)
R: 10.5x19" ET45, 275/35-19 (2% taller than OEM)

[.BMW.]

Originally Posted by kromix

Sounds like the larger sidewalls in the 40 and 35 profile would be a better choice right? More rim protection & less wheel gap? Anything else I should know about this setup? rubbing etc? Leaning towards this now...

F: 9x19" ET35, 235/40-19 (2% taller than OEM)
R: 10.5x19" ET45, 275/35-19 (2% taller than OEM)

You will definitely be closer to rubbing with the higher profile tires. 9" and 10.5" wheels is quite wide for F30.

The best would be if someone here with a similar setup can verify the fitment.

[kromix]

Originally Posted by .BMW.

You will definitely be closer to rubbing with the higher profile tires. 9" and 10.5" wheels is quite wide for F30.

The best would be if someone here with a similar setup can verify the fitment.

Cool thanks! Ill make a post with the subject having the sizes to see if anyone has.

[manari06]

I was told 245 and 275 is good on F30 by EAS.