What size disc for a 4120?

[whitedogone]

I have been looking at a used disc for the 4120. I found a 7 1/2' 24-20 with notched fronts and smooth back discs. Would that be a little large for my 4120? I can get into some hard clays around here.

 

[Turbys_1700]

If you have 4x4 you should be able to pull it...
In hard clay you are not gonna pull it fast...
I have a 5'-6" Howse med duty I pull with my NH 1720 which is a little smaller than your 4120 and it does fine...
I would think that a 6'-6" would be a better fit but if you have a good deal on the 7' disc I would go with it...

 

[dusty3030]

I pull one that big on my 4120 ehydro.
A range 4wd is about a given. No overly strain but you know it's back there.
My soil is fairly sandy so in all fairness I haven't hammered down in any clay.