Should rear tires be bigger than the fronts?

[redrockgina]

I have a 2004 BMW X5 4.4i. I have a couple of questions regarding the tires I should be using on my SUV. I was told to run smaller tires on my X5 in the winter as I will get better traction, so I have 17's on them vs. 19's which I run spring - fall. Is this correct - I will get better traction in the winter w/smaller wheels?

My second question is I was told to put larger tires on the rear spring - fall. Is this correct? I've been running 255/50 R19's on the front and 285/45 R19's on the rear spring - fall. I'm currently in the process of shopping for new all seasons for the spring and I want to make sure I purchase the correct tires.

Thanks in advance for reading my post.

[Mless5]

You want narrower footprint for the winter, diameter doesn't really matter. You might want to look at 225 instead of 255, but you'd calculate height so you end up with the same or very close to being the same overall diamater of the wheel+ tire.

You don't have to. You can run 255/50/19 all around. That way you will be able to rotate them between axels, with staggered set up like you mentioned above you would not be able to do so.

Good luck!