I know its been discussed to death, but.....
I've a 2008 BMW 535xi Wagon 6 speed manual, and I am getting some wheels. I want a 20x9 & 20x10.5 and need to know the proper offset. I am pretty sure the 20x9 will be an ET of 35mm, but need to know the rear offset.
i know the tire diameters need to match for the awd, so I'll
go 245/275.
Keeping the stock ride height for comfort (for now)

Thank

 

On an E60/61 xi car, you can use offsets anywhere between ET 35 and 45. It all depends on the look you want to achieve. What's more important is that the rolling circumference on all four tires needs to be within 1-3% of each other. Use a tire size calculator like this one to play with the measurements.

 

I like your current wheels!
The only thing I would be weary about is having to run a very low profile.
I run a 19x9 and 19x10 with a 245/40 and 265/35 on my 535xi with an et 24. I had to roll my rear fenders a bit with this.
I have to run 19" wheels because of my front brakes being M5 but I wish I could run 18". In my opinion one looses ride quality with the bigger wheels.
Good luck with your wheel search

 

With those widths, youll need ~30-35 offset front and 45 offset rear to keep the wheel face inside the fenders under suspension travel.

You might want to double check rear clearance with the suspension bag as thats a lot of width for rears.

 

Ive got 255/35/19 in the rear and 225/40/19 in the front
I do have ISC coilovers though..

 

Looking good thedood! (Sebastian Right?)
I bought my wagon from your cousin.

 

I run 275 45 18 rears and 245 40 18 fronts lowered no issues at all and

with in the 1% rotational diameter.

 

Are those 513m? looks great! Do the front wheels have a lot of poke with the ET29? and what are you lowered on?

 

Your touring looks great too! What wheels/specs are those? and how do you like the ride with the ISC coilovers, do you just have the fronts?

 

Those are stock 513m and they have very little poke I run H&R lowering springs in the front and I made adjustable lowering links for the rears. Works like a champ and the suspension will still self adjust when loading the cargo area.