I always fasten my crossed trailer safety chains when towing. When I replace safety chains I use shackles rather than the typical OEM "S" hooks. The original hardened "S" hooks cannot be bent open for re-use. I have more faith in screw pin shackles over "S" hooks. Shackles cannot jump loose like "S" hooks may. Good quality screw pin shackles will distort before failure. The shackle allows installation into selected links for chain length adjustment.
I covet any lifting equipment in my possession which is stamped "Made in USA".
If your included "S" hooks don't have an OEM keeper I install them with a heavy rubber band keeper across the open end. Simply slip the multiple loops of the rubber band over the chain, install the hook on the loop, and then bring the rubber band out over the open "S" end. I most often use rubber rings cut from bicycle inner tubes. The rubber over the end helps to prevent jumping off. Electrical tape would also help if rubber isn't available.
We were returning from a regatta the other day when we had our sailboat trailer jump off the hitch ball. A J/22 keel boat approx. 2700# all up with trailer. I'm convinced that I didn't have the hitch properly seated down on the ball. Our hitch clamp is a bit finicky when the hitch is lowered onto the ball. If the hitch isn't kept back while being lowered, it is possible to trap the clamp rather than have the fork be properly positioned under the ball. We were first in to the boat hoist (we won overall with no need for the last race... sorry, bragging) and I went to pick up the trailer alone while the team got the boat lifted. I don't remember specifically looking under at the trailer ball clamp position which is my normal SOP. Operator error is the most likely cause.
Anyway we were traveling on the highway at about 55 mph when we hit a big dip in the road followed by a loud bang and horrible rumbling. I slowed (not braked hard) and slid over to the shoulder with a bunch of black smoke pouring behind us.
The crossed safety chains did their job. The trailer tongue surged under the van and back out while the trailer tongue skid loop dragged along the ground. As I have said all along there was no "basket catch" of the tongue by the chains. The crossed chains did keep the trailer attached and tracking properly while maintaining control. The smoke was from the galvanized tongue skid loop being ground down flat by the pavement.
With two people we were able to lift the tongue and swing the tongue jack back under. The backup plan was to lift the tongue using the small floor jack which I always carry.
Visual inspection of the hitch clamp and other parts showed no damage. We reconnected and continued home without further incident.
Some things I learned.
The crossed trailer safety chains with shackles did their job.
If you don't panic and hit the brakes hard, gradually slowing down allows the chains to get you safely over to the side of the road. Don't be alarmed if you see some smoke when slowing down.
The crossed chains do not at all act like a "basket".
If your rig has a tongue skid plate be certain to check that it is in place and properly fastened. For a time mine was out of place. Fortunately I had repaired it. I'm glad that I did. I'm certain that it saved further damage.
Double, triple check that your trailer hitch is properly seated and clamped on to the ball.
Always connect your safety chains.
Note: Please take any trailer chain specific discussions to another thread than this New (Bee) thread.
P.S. - I was made aware that I misinterpreted the Goodyear Marathon radial "10 psi over" recommendation. It refers to 10 psi over recommended inflation, not 10 psi over sidewall pressure. Back in the days of towing with a station wagon we would run our tires over max inflation so being a bit over didn't seem out of place. I was wrong. (I need to find time to submit revision to a moderator.)