What causes a trailer to dogtail?

Some idiot thought it would be a great idea to put an extra crossmember on 9400i's right where the kingpin would catch it when you pull out from under the trailer. The boss caught it a few times, then last week I caught it and ripped it loose on one side. I hooked it back to the trailer, made a few turns, it caught on the trailer, folded it over, bent it back and forth, and snapped it right off. Problem solved.

I know you're not suggesting we make no turns at all for fear that the rails the tandems sit it will snap off.

 

You mean to say that the tires are not supposed to rotate backwards when backing up? Wow I knew I was doing something wrong!

 

trailer needs alingment most likely. This comes from drivers curbing tires.
You also need to check to make sure you have plenty of gresse on your 5th wheel if it is to dry it will also keep your trailer from pulling straight. and yes jack knifing to tight while u-turning will also cause alingment problems

 

NO. The truck is going forward and while making the turn so tight the trailer wheels are rotating backwards. But why would you care? You dont own it.

 

Most I have seen dog track because of the polymer slider box bushings/pads are wore slap out. I watched a guy trying to back in and took him over an hour because his slider was out of alignment and it kept twisting on him when he changed the angle of the trailer. It was so bad you could see everything twisting underneath.

Sometimes turning in the other direction can be a quik fix but if its bad enough, getting on the brakes hard on the road or a good bumb will just have it dog tracking again. Its a pain in the ### and tends to impair lane judgment espacially on a truck with no rookie mirrors.

 

Freightliners used to have a solid in frame cross member on the very back of the frames but now have them made of a cheap light gauge steel cover that if your not careful to jack the trailer up high enough the kig pin will snag and bend the #### out of every time and then your hooked on the frame. If too low it can be a pain to get the fifthwheel back under it with no room to move.

 

Speed up. The truck is going slower than the trailer causing it to offtrack.

 

I have customers come in all the time for this complain. 90% of the time, it is not an alignment problem. This is a common problem with trailers with sliding tandems. There is simply too much clearance between the slider framing at the under side of the trailer and the tandem assembly sub frame. Some cheaper trailers don't have any bushings at all. Everything back there just starts to wear a bit and the fit between the tandem frame and the trailer frame gets sloppy. Some trailers have those little "J" hooks that wrap around the rail to hold the assemblies close. These hooks are about 6" wide and are at the four corners of the tandem frame to secure it the trailer, but still allow it too slide. Somethings these little guys start to get bend out and get worn. We have replaced them or taken them off and rebent them for a tighter fit.

 

The crown in the road can also cause an apparent dog-track problem, especially with longer trailers.