you know that the lego tires are often too wide for their diameter or the pattern is only street legal and nothing for real offroad driving.
now i have found some RC crawler tires which fits nearly perfect to the 8110 unimog rims.
the tires came from the german manufacturer ansmann and have the number 211000224
the diameter is 108mm and the width is 40mm
or 4,25"x1,45"- 1,9"
they are ballon tires with a very soft rubber compound and with a foam inside
here some pics
if you know some other compatible third part tires, please tell it us.