Newbies - Tips From the Trainer

Sliding Tandems

By Fozzy

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Can you tell me how to correctly slide the trailer bogies?


First of all, you have to determine WHY you need to slide by "scaling" or weighing the truck to gauge what needs to go where and what, if anything, can be done about it. The normal set up is a three axle tractor pulling a 53-foot trailer with two axles in a sliding group. So, if you were looking at the axles from the side, they would look something like this:


After pulling onto the scale and getting the different weights for the steering, drives, trailer tandems and GROSS weight, you can see what you need to slide and if you need to slide anything. I'd suggest reading through the bridge laws thread and see if you can pull some information off of there, too.

We'll say that you scaled the truck and you are overweight by 1000 pounds on the TRAILER axles. You will need to get the weight forward so it can be "shared" by the drive axles. How do we do this? It's like a teeter-totter! You need to get the trailer axles to move to the REAR! This moves weight forward to the drive axles. I'll describe this in steps:

  1. Pull off of and away from the scale and onto a smooth, flat and preferably PAVED or concrete area.
  2. Make sure that the truck and trailer are STRAIGHT before trying to slide anything! If the trailer and truck are not straight, it will BIND before it slides!
  3. Set the brakes and get out. Inspect the sliders and the condition and the positions of the locking pins to determine what type of locking mechanisms you will be dealing with. There are two main types: one with a smaller pull-type handle like a fifth wheel and four locking pins (most common), and one with a longer metal handle that you can get some leverage with and two locking pins.
  4. MARK the position of the pins and where you want the pin to slide to! Many times a driver will pull the pins and slide, but forget the starting place!
  5. Look at the position of the pins on the slots where they ride and ATTEMPT to pull the pins or unlock them. Don't be shocked if they do not move! They usually have been bound up the last time they were slid, or locked into place the last time the brakes were used hard.
  6. If the pins will not pull out, look at them and determine why they are in a bind. You can usually see that they are either against the front or the back of the slot and therefore will not pull out of the hole.
  7. After determining what direction you need to move the pins, get back into the truck and release the truck's brakes ONLY and attempt to "bump" the trailer into moving that direction. After each bump, you must go back and check your progress. NOTE: This is where another driver or a commercial or home made "pin puller" can make this a FIVE MINUTE JOB! It takes only SLIGHT pressure on the release handle to get these pins to pull out after the pins are unbound or freed up.
  8. DO NOT get out the big hammer and beat on the heads of the locking pins! This only mushrooms the pins and makes the job harder.
  9. Pull the pins and lock the pins in the out position. Sometimes the locks have been damaged by a previous driver. Locking pliers can be used here to keep the pins from sliding back in prematurely (and having to start step 7 all over again!). Remember, all of this can be simplified by having a human helper.
  10. Get back into the truck and, using the clutch only (NO ACCELERATION), slide the trailer in the direction desired. In this case (1000 pounds heavy on the rear), you will want to put the truck in low and pull FORWARD to move the tandems BACK.
  11. A good estimate is 250-300 pounds per hole in the slide rail. I'd suggest moving four holes if there is no weight problem on the drive axles.
  12. Slowly move the truck and check your progress. When close to the location, release the locking pins. They will lock into place when the holes line up. When the pins lock in, recheck your weight on the scale.

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