My parents have a three axle trailer and it's a aweful. While going strait, it's fine, but when you turn, you can see the tires twisting under the side loads of being pushed sideways. Three axle trailers do not like to turn!!!!!
I would go two axle with duels if you wanted to carry more weight. I would never own a three axle trailer.
Eddie
I worked in the 5th wheel trailer business for a couple of years, and Eddies words are exactly what we recommended to customers. 3500Lb axles (or 1800kg/4000lbs in Europe) are usually light duty axles, with torsion suspension you can easily bend a swing-arm of the first axle when cornering around a kerb: its two against one, the one axle will give.
When stepping up into the 5400lbs (or 2.5 ton) segment, the axles are already of a heavier duty class, can take much more abuse, the tires are bigger, commercial grade and have a stronger carcass, etcetera.
If you really want HD you need 205/65R17.5 tires which are slightly higher than the 195/65R16 we used for tandem duallies, but because these are tires for medium size trucks, they will last two or three times the mileage of light truck&van tires, with a lower rolling resistance, means less fuel consumption.
When deck height isnt of key importance, we often sold them with 205/65R17.5 as duals on a single 5.5 ton air brake axle.
The only time we sold 3 axle trailers were for market wagons that really needed the low floor height in combination with a 7 ton gross trailer weight, on six 195/55R13 tires. that gave deck heights as low as 25" and still carry 7 ton on the tandem dually...
However, this may be way over the top for private use only...??
I will not even mess with them anymore, just too many headaches and tough to make a dime on.