Crystal wheel / tyre size

Hello I am a member of a boat angling club in Morecambe Lancashire,we run three zetor crystals two 8011 s and one 8045 to launch our boats off the beach.As you would expect we have the constant threat of getting a tractor bogged down in the sand and consequentley covered by the incoming tide.We presentley run 16.9 x 34 rear tyres,can any one advise me on the maximum wheel and tyre size that can be run on these tractors and if wheels from other makes of vehicles can be fitted.

you can stuff 18.4R38 size under them, but also 600/65R38 which is the same height.
20.8R38 doesnt fit under the older models with the old cab.

The hole pattern is the same 8 hole, 275mm circle as any other German tractor (DIN standard)

Throw the old diagonals away and try 540/65R34 that fit on your old rims, and run them at low pressure. It makes a world of difference compared to stiff old diagonal tires.

You could also try fitting twin wheels on the rear. Old tyres with little thread left would do (cheap) as it is flotation you want not traction.