I have loaded rear r1's with 2" bro-tec spacers on each wheel. With good rear ballast my 3320 is a beast.
I'm curious did your tractor come with R1's and 8 position wheels?
No they are set on the middle position and then the spacers were added. I would measure for you but I'm currently a long way from home.If you don't mind me asking
Do you have them on the widest position? I would really like to know the tread measurement . The online manual says 75" on center for the widest position