A few wheel tire questions
 

I have used the search function and couldn't find my answer.

Why do the front tires always have a thicker side wall than the rear tires?

Since are cars are staggered, why is it no one runs say 20's on the rear and 19's on the front? I ask this because I found a set of wheels that I really like, but that widest is 19 inch wheel is 9.5 inches wide, and I want to run a 10 or 11 inch wide rim on the rear. So I was thinking why not run a 20 inch wheel in the rear?

Thank you in advance for any help

its more for comfort, i think...

you can if you want, as long as the outer diameter (or tire circumference) is near stock should not mess up vdc either.

Its because the sidewall profile (eg. 255/35/19 305/30/19) is actually a percentage.
So when you go wider on the rears, you need to step down the percentage or else the tire will be too tall.

So we can probably run 19's on the front and 20's on the rear without VDC hassle? I have always liked this look, may plan that in the future.