Cheap Chinese Springs on Trailers do not equate with American car springs but..I have broken springs, the right side on drag cars but they were pushing2,00 hp and slicks. I've seen a several old cars with broken front coil springs over 72 years.
I don't have any book marks or anything but do remember reading of some broken trailer springs here overtime. Quite a few problems with broken shackles and worn out spring bushings...because or inadequate pieces for the weight and conditions of use Chinese axle bearings such as those I had to remove and replace, with races of two pieces not even meeting in the middle and broken roller bearings. That was on a two axle boat trailer.
The current state of affairs I'm not up on as I don't own a new or old towable now.