[crywolf]

Thanks in advance for the tips and help! There's been a lot of threads lately pushing the boundaries for the 2 series wheel and tire set up but not to much for the xi crowd yet.
I'm looking into new set ups for this spring, trying to run staggered wheels and tires while keeping the rotational diameter of the tires the same to keep the front diff happy.
At the moment I'm investigating a set of 19x8.5 et35 fronts and 19x9.5 et35 wheels, am I correct in thinking those should run fine but the rears will stick out a bit more?
As for tires I'm at a bit of a loss, I'd really like to run 265's out back but I can find a good size combo front and rear that will keep my diameters in check. I'm not to concerned about running the PSS's, they're awesome tires but a bit overkill for everyday, I'll be putting dedicated track tires on the stock wheels later on.
Long post I know, but I'm hoping to help out my fellow xi'ers along the way. :-)

[Luminous]

The rear offset is probably too aggressive. In terms of tires I went with 235/35-19 and 245/35-19, I think if you want 265/30 in the rear you will need a 235/35 up front to keep the diameters in check.

[ABPReader]

The rear IS too agressive. 19x9.5ET45 is perfect, ET40 is a little bit too extrem but ET35 doesn't have any chance to fit properly IMO.

[x233]

Originally Posted by crywolf

Thanks in advance for the tips and help! There's been a lot of threads lately pushing the boundaries for the 2 series wheel and tire set up but not to much for the xi crowd yet.
I'm looking into new set ups for this spring, trying to run staggered wheels and tires while keeping the rotational diameter of the tires the same to keep the front diff happy.
At the moment I'm investigating a set of 19x8.5 et35 fronts and 19x9.5 et35 wheels, am I correct in thinking those should run fine but the rears will stick out a bit more?
As for tires I'm at a bit of a loss, I'd really like to run 265's out back but I can find a good size combo front and rear that will keep my diameters in check. I'm not to concerned about running the PSS's, they're awesome tires but a bit overkill for everyday, I'll be putting dedicated track tires on the stock wheels later on.
Long post I know, but I'm hoping to help out my fellow xi'ers along the way. :-)

I am an xDrive guy. Tried stock staggered summer tires 225/40 and 245/35 on 7.5x18 front and 8.0x18 rear, winter 225/40 and 235/40 front on stock and wider wheels, and 255/35 rear on stock and wider wheels.
Going to use 225/40 front and 255/35 rear summer tires on 8x18 front and 9x18 wheels. Would like to stick with ET40 front and ET47 rear, or ET38 front and ET45 rear.

Looks-wise 8.0x18 ET40 and 9.0x18 ET47 looks just right, ideal, no poking and the wheels are not hidden in the wheel wells on a moderately lowered car. That's equivalent to having 5 mm spacers all around plus a bit wider wheels (0.5 inch front and 1 inch rear). I look at my car again and again and really don't want it to be any more aggressive, maybe 2 mm wider maximum.

I kept the oem front/rear ET ratio of 7 mm and don't think that should be changed. Some would question if 2 or 5 mm would make a difference but I think they do. Moving the rear wheels out using 5 mm spacers the car becomes more stable at speed but I noticed more understeer. Having all 4 wheels out by the same amount makes the car more stable at speed, slightly more effort on turning the steering wheel (which is actually good because the stock is quite "empty") but slightly less agile in turns (which is probably going to be more noticeable the more out you move the wheels).

I also ordered a set of wheels 8x18 ET40 front and 9x18 ET44 rear, haven't tried them yet but I am not sure I'm going to like the rear ET44.

Using a wider rear tire (255/35) on xDrive actually makes the car feel more RWD on throttle (which I like) and is more evident on slippery roads (rain, ice or fresh snow). It "feels" like there's less understeer on throttle because it seems to channel more torque to the rear.

Using a wider and slightly taller 235/40 up front makes braking more effective and kind of reduces understeer, kind of... but at the same time the car feels more wobbly up front, feels taller, turn-in is less precise and less agile, feels like it takes more effort to accelerate, too. So I went back to the stock 225 width. If anything, I'd rather have more negative camber up front than a wider tire.

Making the front tire pressure slightly higher seems to reduce understeer under throttle and makes the car a tad bit more agile in turns. Lowering the rear tire pressure slightly feels like it makes the car slightly more RWD probably because of the better grip.

Rim width. I don't understand too wide. I don't understand 8.5x18 front and 9.5x18 rear if you can be more conservative. Arguably, that looks nice, but I am 100% positive 8x18 and 9x18 look just as nice but don't weight as much. A wider wheel also means it's more likely be damaged than a narrower wheel (both on curbs and potholes). Given a choice, I'd opt for narrower for those reasons.

[crywolf]

That's a ton of good info, thank you! I think I've got the wheels figured out, looking at running a 19x8.5 et 35 up front and a 19x9.5 et 45 out back. Once I get them mounted up I'll see if room allows for a 5mm spacer in the rear which would effectively bring me to that et40.
Now I'm really delving into tires. I love the way my 225/40/17 winter tires fill the wheel wells, trying to find something that's appropriately wide while be taller as well. No plans on lowering so I'm not to concerned with the restrictions there.