Ok I have asked my friend and got some more details.
The SUV has a design problem where the valves hit against the frame. This problem is also mentioned in this reviewhttp://www.online-skating.com/articles- ... i-suv.html
My friend did not notice this problem, so one wheel "broke" not because of a flat tire but because a valve was destroyed.
He ordered replacement tires from Powerslide.
The main use for this skate was to use it on rain and dirt, but this time in Greece it is summer so he replaced the tires with normal wheels.
When September comes he will probably put the tires back on.
He mentioned that they are very slow (some of the push power is lost on the tires) and also that they do not roll on grass well (even though they should)