What is the optimum weight distribution?

Evenly balanced.

 

I agree, well balanced, but good luck with that one...just sayin...

 

Fuel mileage? More weight on trailer (trailer tires/axle have lowest rolling resistance, tandems closer to tractor means they are closer to the 'draft')
Braking? More weight on the trailer
Maneuverability? More weight on the trailer (tandems forward = shorter wheelbase)
Forward traction? More weight on the tractor/drives
Ride (for you)? More weight on the tractor/drives
Ride (for load)? Evenly balanced (to the extreme: slide 5th wheel back for less weight on steers)


Does any of it matter all that much? Not really

 

"comfort" should never but a deciding factor for weight distribution. The tire(s) with the least amount of weight have the greatest chance of loosing traction. Loose of traction equal lose of control. 10k on the steer, 19k on the drives and 34k on the trailer is a dangerous potential jackknife situation. The same load adjusted to 11, 26, 26 would be my goal.

 

Steering axles are designed to have weight,,If you have a 12,000# steer getting as close to 12,000# allows the front suspension to work as designed,,as for the drives and trailer even as possible with a more on the drives,,very hard to get proper braking and traction with trailer tandems having more weight that the drives.
Steer axles and drives do more braking than trailers,, my goal would be 11, 30, 22

 

25 ton in the front hopper and 26 in the back hopper. She rides like a Cadillac and all axles are good on individual weights it realize you probably don't pull a covered wagon but the basics of that formula apply across the board