Hi Claus!
I have also ordered some tires from dakotah toys...The "Trelleborg" are really nice, but seem to be too wide for your row crop project. Here´s another supplier:
http://www.formenbau-traenkl.de/Prod...gen-Reifen.php
(its a kind of copy of the BRUDER types, vou can order them in a soft version (25 shore) to get a good traction...I have them on my MF1155.
OR:
http://www.modellreifen.de/ ...go to "Bilder" ...
At this supplier you can choose the width and diameter...
regards
Frank