I got a simple question I'm sure some one can answer, when laying 2 tracks parallel to each other, how close can they be?

As I am new to this,I'm working on my layout plans & would like to do a double loop.It seems the most popular radius is 11.25" which is fine.I was wondering if I use 11.25" for the inside loop,would I have any problems using 14"radius for the outside loop? Any input would be greatly appreciated