changing a torus

the controls seem to vanish!
when can I change diameters etc?

Press F6 or look on the bottom of the toolshelf just after having created the torus and -before- doing anything else to that torus, as in Blender if you do anything to an object you just added, it will not be possible anymore to modify its settings.

Those settings are only available immediately after you create the object. As soon as you do something else, you can’t get them back.

As sanctuary and stan suggested.
However, if you did something else and say you like to edit a little more.
The basic circle can be edited by rescaling the whole mesh. The small circle can be resized by simply adding a displace modifier. The strength value.

thanks, I used the spin thingy instead