If it were me, I'd use a light suspension with strong axles. IMO, at least, trailer wheels, tires, and bearings are a bit overrated. It's a common complaint in the boat and RV world of trailer tires blowing out, bearings not lasting, and so on. Reducing the load on a bearing by a factor of 2 will increase the theoretical life by about a factor of 10 (varies as the 10^3.333 power for ball bearings; slightly different for roller). More than speed, load reduction will increase bearing life, and using two 3500 lb axles and 1750 lb tires [1590 and 795 kg, or whatever that translates to in Oz availability] with a soft-sprung, equalized suspension would, again IMO only, be the way to go. Which is why I went that way.Neo wrote:In Oz equalized springs are are sold only in sets. Some 7 leaf ones have 1600Kgs rating and other 5 leaf ones have 2000Kgs rating. ... I'm trying to work out what would be the best ones to go for (if I go for Tandem). Based on your experience what rating would you go for?
I calculated the spring rate and capacity of my modified springs, and they come out to somewhere in the 1200 lb range (capacity) each. Don't remember the spring rate, but it's something like 600-700 lb/in, if memory serves, with about 900 lb on each spring. And yes, my 3500 lb [1590 kg] trailer is technically overweight, but they don't normally pull boat trailers over at the truck weigh stations on the highway, and I've never seen portable scales used for boat trailers either, so I'm not worried.
There are even resilient equalizers of various styles (and cost), though mine rides soft enough. These boats are our babies, but they're tough enough to take the ride of the OEM single leaf spring axle, so I don't see a need to get crazy (like air suspension).
Modern torsion axles, by the way, have a variable spring rate. The further you deflect the suspension, the higher the spring rate, unlike leaf and standard coil, which have a fixed rate (progressive leaf and coil is progressive, though). So lightly loaded, the torsion axles are 'soft', but can handle the full weight on either axle when going over speed bumps (for instance), even though they're not equalized. So they also work well in dual axle configurations, as long as they're both loaded equally. And I don't think they're recommended for triples.
As an aside, here's one of many articles on LT vs ST tires for trailers. Perhaps a moot point, if you can't even guy ST tires in Australia, but an interesting read nonetheless. https://rvingwithmarkpolk.com/2012/11/0 ... -lt-tires/