The predominate Class 8 configuration in Europe is a single-rear-axle, 4x2 tractor pulling a three-axle trailer. Tractors, therefore, cost and weigh less than our common 6x4s that pull a tandem ...

My boat trailer can handle a 25-foot vessel at 7,000 pounds, so it's comfortable (and so am I) with my 3,000-pound 21-footer. It'd work even if an axle fell off. Rule 2 ...