Dump valve question

Electric operated dump valves are illegal. If you have 60 lbs of air in the trailer bags to hold up 45-50k and you dump 2 of 4 bags the suspension will drop all the way. Unless you have really large air tanks and fast/large valves to air up the the 2 bags. It is really hard on suspension bushings. It is possible to bend an axle with a dump valve.
Had a buddy with a dump valve and would use it at every turn. And he had to have his trailer rebushed often cause his tire would start to wear funny.
I've pulled a spread for 25 years and I've had a dump valve on a couple and never seen a benefit worth the cost. Never had a turn or a hole I couldn't back in with out a dump valve.

 

I have 2013 Mac 48 102 72k rails Your right it is a nice trailer.

 

Illegal?

 

Mack thought it was a good idea to do that with the power divider. You do not want a buzzer. Your headache will thank me later

 

I agree with @johndeere4020 "Illegal?"

I've only been doing this for about 30 years so who am I to know the laws. I know that may years ago a couple of states (I think Georgia was one of them) where you were limited to 34k on a 10' spread IF you had a dump valve on ONE axle that could be operated from inside the cab. Back when I pulled a reefer and ran the PNW to WI we got paid by the box count. One could legally run 85,500 in the western states, all the way to the ND/SD - MN state line. MN and WI only had axle scales not full platforms so we roll up on the scale with the rear axle dumped then as soon as the drives got off we'd switch axles and put air to the rear and dump the front moving the weight forward or just dump the front so both were flat (Ever notice guys pulling spread axle reefers running down the road with mud flaps that seemed too short? That was so they wouldn't be dragging when dumped rolling across scales). Took a really KEEN eyed scale master to catch this. Valves, lines were oversized and vented inside the trailer. Worked great till some young gun at the LaCrosse scales got smart and would stand out there next to your trailer with a broom handle and poke the bags with it as you rolled across. If he found low/flat bags he'd pull your pigtail('s), have you circle the scale and weigh again. I got an overweight ticket once but never got a ticket for having dumps.

As for a blanket being "illegal", I don't think manufacturers would install single axle dumps from the factory if there was anything deemed illegal by having that. For a period of time every one of our new flats and SD's came with a single axle dump from the factory. Had a separate pigtail connection on the trailer and many of our T-680's even had a switch on the dash designated specifically for this, also from the factory. I haven't pulled any of our newest trailers so I don't know if they are still specing them that way.

 

Electric dumps are illegal. If you have a short in your trailer it well dump the axle and will effect your braking ability. Everyone that has ever had a dump on the back axle knows that if you forget to air it back up and you hit the brakes the tires lock up and you get flat spots on your tires and smoke roars. Not so much flat spots with ABS today. If you have a 12v wire for say a marker light or tail light rub through and ground out this can cause your electric dump to dump the axle and compromise your brakes. Hence illegal.
When I bought my 1998 East they would not install a rear dump valve at all period.
My 2005 Ravens magnum I bought new came with a suspension dump and a rear axle dump and an extra 4 wire pig tail. HOWEVER it was not wired from the plug to the rear axle dump.Everything was there but you had to run the wire from the 4 wire plug in the front to the rear axle dump valve and hook it up yourself because it was not legal and they could be sued. The suspension dump was mechanical and was mounted at the dolly legs so you had to be out of truck to use. I never hook up rear axle dump.
Go to Dover OH or call if you want and ask them to install a lift on your spread and they will tell you mechanical only operated at the dolly legs. They will (or would) set it up for electric but you have to wire it cause it is illegal.
Trailer manufacturers use to install electric dump valves but don't any more and if they do they haven't been educated yet. Same with lift axles, has to be mechanical.
Go across IN with something light on your trailer and have your spread in the air and the right cop will stop you and will want to know how you make it go up and down.
In OH they run 5-6 and 7 axle dump trucks with steerable lift axles and all controlled with mechanical switches, no electric.
I do believe in MI same thing.
I know all about cheating the scales with dump valves and extra axles. My Pete I have used to be my Dads and he pulled a 4 10s. That's a 48' 4 axles 10' apart. Legally haul 130k I think in MI. Truck still has the mechanical trolley valves so he could "walk" 130k" on to the OH TP as 80k. Or 80k as if it was empty for cheaper toll. You would put a bypass on the air governor and build as much air as the compressor would build, put as much air as it would in the 2 forward lift axles till the drives crossed then dump the lifts till they crossed then put the air to them to get the spread and back axle as light as you could. You have to have large air tanks (100 lb propane tanks were a favorite) for each axle for the volume of air needed. You need large/fast valves and you had to have large air lines going to air bags including removing and replacing the holes on the airbags. The bigger everything was the faster you could move air the more you could haul.
Anyone know what a spring air is? Popular in PA especially. Spread axle was on beefed up spring ride and back axle was air ride. Same principal, drop air in back axle till drives were across scale, put as much air in back axle till the spread was across the scale on PA TP and then dump it before the back crossed. Good for and extra 10k payload or cheaper toll. This is why they invited dumps valves. Nice slow straight forward movement.
Now days TP charge by how many axles and allow the DOT to work the road. Back in the day, if you got on the turnpike you were home free till you got off.
Putting a dump valve on a run of the mill trailer and start twisting and turning and backing it in on a jack is not good for a trailer.
Put a dump valve on an axle, load the trailer to 80k gross, air it all up and then throw the switch jump out and walk back there and see what happens. First thing it does is goes clear down to stopper blocks inside the airbags. This not a good state to be moving the trailer in. But stand there and watch and time it and see how long it takes to air the spread up enough to pick the trailer back up, IF I repeat IF it picks it back up. It will depend on what and how it is loaded. Now if you have 45-50k belly loaded in 10-20 feet it probably will pick it up. But if you have good tires and go backing it in to a jack it will start hoping and jumping and jerking cause the back axle griping releasing gripping releasing as you go. I cringe when I see guys do this.
I say if you can't get it done without a dump valve maybe you need a little more practice.
It's your trailer though so do what you want to it.

 

So no evidence of their illegality? A normally closed valve which is what is on trailers from the factory has to be energized to open and dump the suspension.

 

I have no need to provide any evidence. You can do what you want, it's no concern of mine.
I'm just sharing my experience, I know for a fact 2 major trailer manufacturers will not install an operating electric dump valve. And I also shared why they told me they wouldn't. You can probably find a dealer to install one. I don't know. If you need help from a dump valve to back your trailer up by all means have one installed or install it yourself. I'm all good with what you do.