Whats good 5Series,

I currently have 225/50R17 wheels/tires on my E60, now i was thinking about getting 18's but i'm not sure if I keep the same tire size or do I go with a smaller tire.

 

It depends, if you go square setup the recommended size is 245/40R18 or if staggered 245/40R18 front and 275/35R18 rear.

 

Ok, but what's The difference between staggered and square. My wheels are five lug which I can imagine are staggered & I have all wheel drive so all my tires have to be the same size or it'll throw off the DSC.

 

staggered just means your rear tires are wider
I used to worry about staggered with AWD too.. dealers will tell you not to.. any custom "pimp my ride" type company along with people in this forum will tell you its fine.. just can't change the rolling diameter of the back tires..

Mine are 9" in front and 10.5" in back
AWD and all is fine

 

I'm running 245/40R18 front and 275/35R18 for my summers on an XI and all is fine. ET35 front and ET33 offset rear.

After doing lots of reading on the custom wheels XI thread, I'd recommend that setup.

 

Correct me if I'm wrong, but just to clarify, the offset will change based on the rim you get. If it has lip on it, if it's concave, etc. So you can't just pick an offset based on someone elses rims unless of course you're getting the same one.

 

Correct. The offset is fixed to the wheel. Didn't mean to confuse.

Although, if OP does have an XI, he/she will need to be mindful of a suitable offset due to our setup.

 

Aight forgive me because y'all used a lot of terms that I am still learning (I came from a Honda) I have a 07 530xi

 

I had to re-read this thread like 6 times to understand you guys, but I think I got it. I want to know how do you figure out the rolling diameter for the front and back tires

 

http://www.1010tires.com/Tools/Tire-...0R18/275-35R18

First column shows your stock tire size. 2nd Column shows 245/40/18. 3rd column shows 275/35/18

Overall diameter I believe is the field you're looking for. (it's in that table)