From time to time I will pull my tag a long trailer empty. My biggest fear is locking up the trailer brakes. I've only done it one good time about a year ago while on the phone in a serious conversation while going down a divided highway and the light changed red. It wasn't pretty and it was my fault for not being white knuckled approaching the signal. The smoke and the smell of money and disgust lingers a long time. The other couple times were very minor because my eyes were glued to the road and the light changes to red and I just barely left some rubber and smoke but couldn't let up on the brake pedal. I have also ran a few yellow lights knowing that if I hit the brakes they would lock up. I expect lights to change red and treat them like that but sometimes it's just too much. My trailer is an ABS equipped Eager Beaver 20 ton and I have a lowboy also with ABS but I'm not sure if it works really. Bottom line question is can I disconnect and cap the service line and rely on the truck brakes? Would that be legal if you can do that? I realize you'd have to leave the emergency line connected to keep the brakes open and maybe just use a glad hand with a plug on the service line to keep the air in the system. My rationale is the trailer only weighs 4 to 5 tons and the truck is designed to carry 18 tons on the truck brakes alone. That way if a light changes red or a car pulls out in front of you you could smash down on the brakes hard and stop yourself a lot quicker and safer than locking up 8 tires on the empty trailer. Also you could potentially ruin $2k to $3k in tires. Also an empty tag a long being 4tons and an empty lowboy usually being 8tons or more is a different story. The tag a long is going to lock up much easier during a big braking situation.
Been doing it like that for years. Getting caught would be a automatic red tag and a bunch of points but who cares, its easily fixed
The short answer is you already Know better
I take you have never had a trailer try and pass you when you slam on the truck brakes with a empty trailer!!!! DONT TRY IT ITS NOT A GOOD THING TO SEE A TRAILER COMING AROUND THE TRUCK IN THE MIRROR!!! it don't work like you think on a wet road, dry might be ok but im to scared to try it now
True on the wet road I guess if you're referring to a jack knife when you say trailer passing you.?? Really sucks there isn't a way to avoid it. I mean we have roads that are 65 mph and covered with red lights. I hate the feeling.
I just wonder if one of those old school front brake limiting valves would be the ticket, you know, the ones that say dry road and slippery road.
That is a good thought or just plumb it with a 3 way ball valve on the tongue somewhere that blocks off the service line from the truck and sends the service line from the trailer to atmosphere so there is no chance of bottling air in the trailer service system. Mount it somewhere where it looks like it belongs and DOT need never know about it. You may try this at your own risk of course
The problem with ABS is it's reference, if it has sensors on all four wheels, and you dynamite the brakes, they all lock up. If all four are stopped, the ABS will never cycle, it has to have one rotating wheel for speed reference to know if any other wheel is locked up and sliding. The Dodge dually I had with factory rear wheel only ABS did that, one good hit and after that you had a toboggan. There are several ways to limit the trailer brakes, best thing to do is consult an outfit that specializes in nothing else but brake systems.
Not legit but would work, as long as you remember to engage the brakes when loaded.
only time a trailer has tried to pass me was with brakes locked up. disconnect the line and it stays back there where it belongs
Ideally it would be great to unhook the trailer service lines. If it's wet in a turn under an immediate stop yeah it could jack knife I assume. Bottom line for me is I will never ever do anything illegal because if it went bad I'd be in prison for neglect. The best solution I've found is to have the truck brakes adjusted really tight and just treat every light like a red light. As the guy paying for tires it's nerve racking. It still seems more dangerous to have the rear tires all locked up in a sudden stop. The trailer weighs 8,000 lbs and I'm sure 2,000 lbs are on the hitch so all that braking designed for 20t is only for 6,000 lbs empty. It's just a matter of time. They should have a reference for the ABS on the truck wheels.
Yeah, I'm sure your insurance company wouldn't like the brakes "faked" either. Even though I can adjust the electric brakes on my 14k GN down to nothing when empty, I still have them on a tad. I haul with a one ton and go through front brake pads pretty quickly if I don't. I've also flat spotted two tires in an emergency stop enough to waste them. I guess it's all part of the game.
Is there not something available to install on the trailer to reduce the air pressure to the trailer brakes when it is unloaded..? Have you asked the trailer manufacturer..? I've seen them referred to as "light laden valves" before. Basically you mount the valve on the trailer frame then hook a linkage up between the valve and one of the trailer axles so that the more load you put on the suspension the more air pressure it allows to the brakes. Semi trailers all have them, why would one not work on a tag trailer..?
Sounds like the easiest solution would be to just drive better.
Yair . . . Okay, I am showing my age and ignorance but I can only assume things have changed since I drove trucks . . . once was the time you could brake the trailer (hand control) or the truck or both together, has that changed and there is no independent control for the trailer? The first three trailer train I drove had a separate circuit to the rear trailer so you could apply a bit of brake down the back there to jerk everything into line if you got a bit of a wiggle on. I understand the problem but don't savvy why it's hard to fix. Like JNB I had electrics on a tandem behind my pick-up and they were just dialled back a tad when running light. Cheers.
Scrub, Most trucks with air brakes here still have the hand lever to activate trailer brakes separately, but when you apply the foot brake for the truck you get trailer brakes also, and no way to vary it, what you get at the truck you get at the trailer. Electrics are a whole different ball game.
Yair . . . Gotcha lantraxco . I seem to remember a three position control, either/or or both. Maybe I'm dreaming. The thing I don't quite understand though . . . every driver of a gravel rig pulling a dog or pig spends half his time running empty. Surely they all not stressing out worrying about flat spotting tyres at the lights . . . what am I missing, what's the difference with a tag? Cheers.
I'm wondering if you could incorporate an old manual style front brake limiting valve into your trailer service line on the truck, when empty you would have it flipped to slippery road, and loaded flipped to dry road. Not sure if it would be legal but might be worth checking into!
another thought is leave the trailer with the tractor instead of taking it home!!
The brute force method would be to crawl under and back all four slacks off, LOL Knowing me I would forget and it would dawn on me loaded downhill into a hairpin..... been there done that, lived to tell the tale!
Bump from the past. I'm having the same problem on a tag trailer with tandem 15klb axles. Empty, the trailer is under 9klbs. Empty, much over 10-15psi locks the tires, loaded with ~21-22klbs it will still slide the tires not much above 30psi.
A PBR brake controler can solve the problem, it even has a bias control that is operated from in the cab.
Check the cracking psi on trailer relay valve against the cracking psi of tractor relay valve. Make sure that both valves have the same cracking psi. One other thing to check is if for some reason this trailer has a speeder valve installed before the brake relay valve. The speeder valve will probably be a Sealco #110570 or 360. Speeder valves can start freezing up because of moisture, When applying brakes they will or can suddenly open the control port side causing the relay valve to instantly rush air to the brake chambers.. Truck Shop
Thanks, Truck Shop, I'll look into that. This trailer is less than 2 months old, it's done it since new.
My first thought was cracking pressure on the truck. I had 2 nearly identical '84 Volvos (forgive me father for I have sinned ) Any way one had great brakes and the other you had to stand on the pedal to stop. One day the one with the bad brakes wouldn't build air, leaking relay valve. Ok called the Volvo dealer and ordered a new valve by VIN. Installed new valve and surprise! the dang thing had brakes. The old valve had twice the crack pressure the build sheet called for. Didn't skid any more trailer tires.
Dang Zucker you owned two Velveta's. One other thing to check is are both axles set up with sensors or only one axle. Because if it is a single axle ABS and they hooked up the modulating valve to the axle with no sensors it basically renders this system void. And this happens more often than you think. We have 10 53ft three axle trailers we just received from Utility that have to go back and be reconfigured. They put the sensors on the wrong axles and plumed the modulating valve to the wrong axle also. This is the second time this has happened. We inspect every new trailer we buy. Truck Shop