Here is my question, I now have the R4 tires and want to go to R1 ag tires. I can't figure out why the rears will be taller but the fronts will be lower than the R4's. It seems that would throw off the ratio between the front and rear. What am I missing?
I think the numbers on the L3400 are the same as for the L3200/L3800. The R4s diameters are 40.5 and 27. The R1s are 43.2 and 29.1 (for 11.2x24 and 7x16).
The parts manual lists the tooth count for every gear in the tractor. It is a tedious process, but you can come up with the actual gear ratio, rear/front. I did the counts, and got 1.5526. Kubota says 1.56. The R4 tire ratio is 1.50, the R1 ratio is 1.48. Kubota saya they like the front tire to be running about 5-6% fast; either of these ratios work. You want the tire ratio to be just a bit smaller than the gear ratio.
Kubota uses a lot of TITAN tires. Their web site gives a pretty full set of specifications for their tires. Pay some attention to the number of PLYs, and the load rating. You need 6 or 8 ply on the front if you have a FEL. My loader weighs about 1160 lbs empty. Since its center of gravity is in front of the front tires, the front axle is the fulcrum, and you have over a ton on it, again with an empty loader. Toss in the weight of the front half of the tractor, and you are well beyond the rating of the 4 ply tires. Something to think about...
I went for the R4s for the load rating, but I've really regretted the choice. I'd love to make a trade to R1s. But get plenty of plys.
I understand your explanation but the specs call for R1's with 11.2 24 rear and 5:00 15 on the front. I have them on now 6 ply on front and they are about 2 inches lower than the R4's. something does not seem right.
The 5x15 front tire is for 2WD. If you have 2WD (L3400F), the tire size ratios do not matter. If you have 4WD (L3400DT or L3400HST), the front tire is 7.2x16 (tractordata.com calls it 7x16 in their detailed specs).