Looks good. How do you know the tire circumferences are correct for your gear ratio?
Well, on paper they should be fine.
The 23x8.50-12" matches the 6-12 tire (6-12 is listed as the factory R1 AG tire size for the front of a B8200). Both have circumferences (listed on paper) of 68.9".
The 23x8.50-12 tire has a listed diameter of 22.6". Multiply that by 3.14 to get the circumference and you get 70.96".
The 12.4-16 (listed factory R1 AG tire size for the rear of a B8200) has a diameter of 37.2". Multiply that by 3.14 to get the circumference and you get 117".
To get the ratio....
117/70.96 = 1.648. Which is a 2.58% difference from the B8200 gear ratio of 1.691
Here is the calculator i used to find the percentage difference, between the two interactual gear ratio numbers....
https://www.calculatorsoup.com/calculators/algebra/percent-difference-calculator.php
Hopefully i have done my homework correct.
The only variable i don't really have control of, or know, is the width difference between rear wheels used on the turf tire and the rear wheel used on the R1 AG tire. That should change the height slightly (depending on variance), which will change the circumference slightly as well (wider wheel lowers overall height and narrower wheel raises overall height). I do not think this difference is enough to have a detrimental effect on the relationship of everything, as a whole. Guess i'll find out.
Playing with numbers (because of the wheel width variable), just for poops and chuckles....
If i add 1/2" to the height of the rear tire (theoretical narrower wheel) making it 37.7" tall, then multiply by 3.14, i get 118.4" circumference.
118.4/70.96 = 1.668 gear ratio, which is a 1.37% difference from the 1.691 gear ratio.
If I add 1" to the height of the rear tire (theoretical narrower wheel) making it 38.2" tall, then multiply by 3.14, i get 119.95" circumference.
119.95/70.96 = 1.690 gear ratio, which is 0% difference from the 1.691 gear ratio.
If i subtract 1/2" from the height of the rear tire (theoretical wider wheel) making it 36.7" tall, then multiply that by 3.14, i get 115.24" circumference.
115.24/70.96 = 1.624 gear ratio, which is a 4.04% difference from the 1.691 gear ratio.
If i subtract 1" from the height of the rear tire (theoretical wider wheel) making it 36.2" tall, then multiply that by 3.14, i get 113.67" circumference.
113.67/70.96 = 1.601 gear ratio, which is a 5.47% difference from the 1.691 gear ratio.
Seeing a 1" difference in overall height would be one heck of a stretch (pun).
I can only speak in hypotheticals here but i don't believe there will be anything near a 1" tire height difference when mounted, between the width difference of the narrower R1 AG wheel and the wider R3 turf wheel.
YMMV but that's my educated guesstimates and theories.