Almost all "hard rubber" wheels are, at their core, EVA foam-filled. To make the wheels all-rubber would make the pram incredibly heavy and also quite expensive - there are such, e.g. on the Seed Papilio, but it is just a layer of rubber again (no foam, though)... Anyway, read more about different wheel types HERE.
We always write as much as possible (from measuring ourselves to taking info from the manufacturer), however, in this case, I cannot tell you the exact measurement as I did not come by any (and did not have this exact model in my hands). From my experience, I can make an educated guess and tell you the wheels are about 18 to 20 cm in the front and about 25 cm in the back. They will be MOSTLY urban wheels, so for smoother surfaces plus occasional grass, cobblestones, other bumps... I wouldn't get this for harsh terrain every day. The mild suspension also adds to that feeling. Some dirt roads and trails you'll be fine with, but if you will tackle multiple longer ones everyday I would rather look for inflatable wheels or foam-filled tires (actual tires) - or think about a three-wheeld or all-terrain four-wheeled stroller (more about the difference HERE).