We had duals for our 180, silly me got rid of them when I quit using it on a disc. Now wish had them back. They were 18.4x28". 

He's the duals on my WD45. I just wish I had 8" spacers instead of 10"

My Great uncle had different duals on this WD45 years ago. He put wide tires on it and used to to break open wet muck ground to let it to dry.

I have a set for my 185 too but I never tried to mount them.

I like plowing with the left dual on too. I have 3 weights on each side instead of fluid, and the dual really helps.

200Tom1 wrote: soil packing.

This is where duals REALLY make a difference.  By spreading the tractive effort over larger surface area, the path of travel is compacted substantially less.  Soil distributes load based on surface pressure and the 'cone of compaction'... meaning, if you put 100lbs on a round spot of soil, then measure the compaction underneath, you'll find that the compaction force on the soil below is spread out in a cone with basically 45 degree angles... and as you travel down that cone, the compaction result drops considerable (based on the increasing diameter of the cone).

Rolling a tire along a path, creates what is essentially a 'curb' of compacted soil, where the higher the pressure, the deeper the cone reaches, and the tighter the compaction occurs.

By increasing surface area, running duals doesn't cut that compaction by half... it cuts it into quarters.

As noted, having a dual on ONE side when plowing, helps balance draft.

Running duals on both sides also effectively lowers the roll-center of a tractor, by moving mass AND by moving support farther away from it's center axis,   If you're working across a grade with a narrow-front, running duals will have a significant effect on lateral stability.

re 'hard on driveline'... is a relative thing.  'what it's designed for' is not a particularly well-defined thing.  While having duals mounted increases likelyhood of stresses in some aspects, the design criteria for 'real' tractors takes into account much greater tolerances for overload than say, a Toyota Prius.  A tractor that's plowing through a field, regardless of wheels, etc, that hooks onto an imoovable rock or stump, will stop with an astounding yank... and the shock forces are really high.  Frankly, the loading which occurs from pulling an ordinary plow through ordinary soil isn't easily 'calculable', because there's so much variablility across the agricultural landscape, that one can't just assume a particular value and 'build to it'.  The only way to survive that, and all the other crazy things that occur in the realm of agricultural work, is to have plenty-more-beef there than MOST of the time.  Anything less, and you wind up with a Ford N or a Kubota.

There was a local guy that ran duals on a WD45 but no spacer , that was a "BAD ASS" looking machine also