Eagle Library: Pads with diameter different from auto

I try to make my own library for a special part. This part needs a pad that has a diameter that is smaller than the auto setting. For example: drill size 0.031496" with a diameter of 0.04". In the library editor the pad is displayed correctly. However when I use the part in the board editor, all the pads have a diameter that corresponds to the auto value. How do a solve that problem, such that the pad has the smaller diameter? Thanks for the help.

You have to adjust the min pad size in Design Rule Check.