I have a 2008 X 2 door. It has a 4.5" lift and 35" BFG Baja T/A's. Yes, these are the actual Baja's that sell for $500 each. A buddy of mine won them in a raffle and I scored them pretty cheap. I know they are a heavy tire, but not sure how heavy they are. I really want to go to 37's, but I use my JK as a daily driver and I'm a little concerned about 37's. I wheel my Jeep at least twice a month on moderate trails. I have been looking at tire weights. There are some 37" tires out there that actually considerably less than most 35's. I really like the Swamper M-16's. They seem to be a fairly light weight tire for a 37. So, here's my question:
Is it the tire weight that usually causes problems with the D30 or the actual diameter? If my 35's weigh more than a 37" tire, wouldn't that actually be easier on the D30?

 

Good point. Any other opinions?

 

Both the weight and the radius matter. The larger mass takes more torque to rotate under any condition (and to stop while braking) and the larger radius can generate more instantaneous torque on the axle as the tire slips and suddenly gains traction.

 

As of now, I have 35" tires, 3.73 gears, 6 speed, and an open front D30. My plan is to run 37's, 4.88 gears, and an Aussie locker in the near future. I know 5.13's are the ideal gear for 37's, but the gear teeth are just too damn small. I'm hoping the 4.88's will be sufficient and give me a litte more tooth size than a 5.13. My theory is that with the locker, lower gears, and 37's I'll be able to finesse the Jeep over obstacles easier than the 35's and open front. Do you guys agree, or am I simply building a ticking time bomb?

 

If you are conscious and careful (finesse) of the way you drive, you can get away with that combination and others, but that combination of parts is not going to overcome the weaknesses of the D30.

Protecting the differential with a conservative gear ratio will not make the shafts stronger, whose failure is more common (in stock form).

The larger radius of 37" tires can generate more torque than the 35s. The increase in torque will be more than any advantage gained in climbing over objects unless they are relatively small.

Adding a locker will raise the torque level within the drive line in many cases, since spinning the wheel with least traction is not an option.

 

Bone those baja ta are really heavy. Probably heavier than most 37's you can buy today.If I am not mistaken one tire is somewhere around 150lbs, not including the wheel. Looked at those tires when I had my prerunner and the tire was just too heavy for the truck and daily driving. Just my opinion though and I hope you get your answers. Good luck

 

That's true, they are heavy, but I don't think they are 150 lbs! I have not weighed them, but I know they were just a little heavier than my old tires (Cooper STT). I agree, they are probably comparable in weight to most 37's and probably actually a little heavier.