brake question

Back in the day when trailers only had service pots you would "dynamite" the trailer brakes when parking. Basically the relay-emergency valve on the trailer would sense the pressure loss in the supply line and send full trailer reservoir pressure to the service brakes to apply them. Of course as time went on, the trailer air would leak down and the brakes would eventually release.

It was only really designed to get a trailer stopped in a breakaway scenario and not long term parking. This is why school teaches you to hook up your airlines, charge the trailer and apply trailer brakes prior to hooking up. Just in the off-chance you are trying to back under a 45 year old trailer without spring brakes.

 

I was actually never taught that. Haven't ever pulled anything that old but now I'll know if I ever do thanks

 

Look for split rims. It's a give away. Spring brakes became law in 1983 or 1986, I can't remember which,so they still aren't that old.

 

Then if you look at logging trailers (the pole type) some had no spring brakes well into the 90's believe it or not. Came that way right from the manufacturer.