Dump valve question

I would. Dumping the front puts more weight to the truck where you have 2 axles to take up the weight. If you dump the rear, the vast majority of the weight would land on the trailer axle. Big weight concentrated, like a 45-52,000lb coil or crane counterweight and the like, would be getting uncomfortably close to the tire ratings spread over 4.

 

You would blow all 4 tires off the rims before you would ever hurt the trailer. I can’t see any difference between the U.S. market Mac’s and our 12’ tridems and we put 72-75,000 right in the middle of those all the time.

 

If you are setting up remote switches in the cab you dump the rear axle. You want a rear dump to shorten your wheelbase for tight turns. Slow speed maneuvering on a single axle isn't going to hurt it.

Having separate dumps for both axles is good for when you are unloading a single heavy piece. Helps avoid overextending the airbags when unloading. While they might not pop the first time over time you will stress the rubber where it attaches to the pedestal and reduce the life of your bags. Eventually they will fail right at the pedestal.

 

Set it up so you can dump either axle, or will make it easier for backing and getting your trailer into spots if you can do that. I pulled a 52ft spread cattle trailer set up that way and I could get it into almost anywhere I needed to. Even loaded right to 40k on the spread whatever axle isn’t dumped won’t have so much weight on it that you would be damaging anything. We’re not talking about driving all day like that.

 

Also not a bad idea to have indicator lights for the switches in the cab so you don’t forget to inflate the bags. It’s easy to forget until you get in the habit of dumping/inflating them.

 

Or a buzzer

 

I’ll admit I’ve driven a while with the back axle dumped after making a turn. Things happen when you get tired.

 

I used to lease to a company, their older trailers the dump on the rear was on or off. The new trailers the rear would dump but would auto re inflate over 3mph. According to their shop foreman, someone was heavy and rode from Baltimore to Maine with the rear axle dumped, according to him it ####ed up the rear axle suspension and rear axle to the point it needed replacement.

4 bag auto dump when brakes are set is helpful for heavy load loading and unloading. It can be a pain, as noted, when putting the trailer on a dock. In that case, driver sets brakes on trailer only, fully deflates, leave it in reverse and then quick charge the trailer and reverse against the dock then re apply trailer parking brake. Might take twice to get it fully deflated and tight to dock.

Two independent dumps on switches would be helpful.

 

When I drove for H&W I drove a 1987 cabover Kenworth pulling a 48/102 flat with side kit. Hauled a lot of train wheels for csx then. Loading the wheels we dumped the bags on the tractor, unloading the train wheels we dumped the trailer, usually unloaded us with a forklift from the rear. Making tight turns we dumped the rear axle of the trailer. Front lift axle on the trailer is good if your doing some major dead heading.