You are swapping all the numbers around
If you have R1 8.3-24 or 12.4-16 rears, you need R1 6-12 fronts.
If you have R3 or R4 13.6-16 rears, you need R3 or R4 23x 8.5-12 fronts
If you have R4 12.4-16 rears, then I don't know what size front you need because that's not a valid combination.
23 x 8.5 - 12 will more than likely be much too large.
Do you already have R4's on it?
As R4's will not mount on the 16" rim from an R1, they are too narrow of rims.
If you do already have R4's on it you will need to find out the RC of that time to determine what the RC of new front tires needs to be.
The tractor had the original turf tires on the rear 13.6-16 and then the fronts got changed to R4 from turf.
the rears that I have now are 12.4-16 that I got from a new B series tractor.
the rears fit perfectly but the fronts have a different bolt pattern and center hole compared to my 1995 B 2150.
I bought the set of 4 tires from a new tractor.
The fronts were 23x8.50-14NHS. I have 1 good rim that was replaced years ago that was stamped D.I.D. Japan 12x7JA . The other is the split rim from the original turf tires.
Out Kubota dealer said the rim I am looking for is $600+ .
looking for options or used one.
I don’t think the split rims were intended for use with 23x8.50-12NHS tires.
way to much side pressure. They will crack at the lug stud.
