How do you know when to and when not to slide tandems?

Discussion in 'Questions From New Drivers' started by Flankenfurter, Feb 9, 2021.

  1. Flankenfurter

    Flankenfurter Light Load Member

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    New guy not driving yet, but I just have to ask because I'm curious...

    [Dry Van/Reefer]
    I understand sliding tandems for weight distribution and bridge formula, but I see (couch driver now) tandems being slid on YouTube videos. I don't understand how and when they know to slide them -- say at the drop off location. I hear drivers say the company wants them to slide or not slide.

    I'd prefer not to have to get out and slide them every time I drop off a trailer, but is it better to do so? Will I have to slide my tandems forward every time I pick up a trailer?

    I'd like to hear your experiences. Thanks in advance.
     
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  3. uncleal13

    uncleal13 Road Train Member

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    If there’s too much weight on trailers , you slide axles back. Too much weight on truck, slide trailer axles forward.
    Also some loading docks want them all the way back.
    Also one shipper I was at , the driveway was so steep I had to put them back to keep the bumper from dragging on the ground.
     
  4. Dockbumper

    Dockbumper Road Train Member

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    Stay away from too many youtube videos. Sliding tandems is a regular.....or at least semi regular occurrence. It is not Rocket science. Takes almost ZERO time out of your daily tasks. While you are on the couch, start studying for your CLP. Concentrat on the important stuff!
     
  5. Six9GS

    Six9GS Road Train Member

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    You sure asked alot of questions!!!! That's a good thing, it means you're thinking about all this stuff. Keep it up and you'll do well!!!
    1. Some shippers and receivers request you slide tandems all the way to the rear before you back up to the dock. Some don't. If they don't ask or otherwise let it known to slide tandems back, I usually don't. Sometimes I'll look at the other trucks in the docks to see if they have theirs slide back.
    2. It is basically easier to back a trailer, especially in limited space, with the tandems forward, not back. However, the farther forward they are, the more trailer swing out you'll have and that can complicate things too. Especially since the swing out, when you are doing a normal back into a dock, will be on your blindside. I find I generally prefer around the 40' mark. Others may have different preferences.
    3. Some state have laws regarding how far back the tandems can be. In California, where I commonly run, you can't have your tandems back farther than 40'. In some states it is 41' and in others, they don't care. That will effect your ability to distribute the weight to get your things legal. But, it is what it is. If you're in California and have your tandems at the 40' mark and still have too much weight on your tandems, you'll,have to go back to shipper to get the load fixed, there's nothing more you can do. They'll either have to redistribute the cargo or remove some.
    4. In the beginning, you will probably have to slide tandems more often. After some experience you get a feel for things and often able to stab the tandems where they need to be, or get pretty close. Alot of that will depend on what kind of cargo you haul. I haul refrigerated freight. I am usually heavy. For me, I find the 40' mark is usually a good starting point. But, if when I go to close the trailer doors, there's quite a few feet in the back of the trailer without cargo, I'll probably have to slide them farther forward. There is no set rule. How much cargo and how the cargo's weight is distributed will always be different. So, you can only swag (Scientific Wild As- Guess) it until you can get to a scale to get your actual weights. But, with experience you swags will get better.
    5. As mentioned, moving tandems forward takes weight off drive tires and adds to tandems. Sliding back does the opposite. It may even be necessary to slide your 5th wheel. This will distribute the weight between your drive axles and your steer axles. Fortunately, I haven't had to do that often. But, with tending to have heavy loads, it does happen to me on occasion.
    6. The tandem rails on some trailers have holes very closely spaced. General rule of thumb is you move about 250 lbs for each hole. Other trailers tandems rails have holes spaced farther apart. General rule of thumb is each hole will move 500 lbs. However, it is only a general rule. How the cargo is distributed effects that and no two loads are identical. I have slide tandems by 1 hole and moved 900 lbs and on another occasion moved 200 lbs. So, it's not a good idea to scale, figure out how many holes to move, move them and head down the road. Reweigh yourself!
    Hope this helps and keep asking questions!
     
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  6. Flankenfurter

    Flankenfurter Light Load Member

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    Thanks so much for the informative reply. Really helps. I'm a believer that curiosity kills 8 of a cat's lives. It's the 9th life that really matters.

    Seems to me it would be easier if your tandems were back. Less swingout. Easier to get in the box, no? I know this is stuff I can ask my trainer, I'm just trying to get a jump start to get thoughts going.
     
  7. Dockbumper

    Dockbumper Road Train Member

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    I prefer to back between two other trailers with my tandems all of the way back for just the reason you stated, tail swing.
     
  8. ZVar

    ZVar Road Train Member

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    Easier is a misnomer....
    With the tandems forward the trailer turns faster so it needs less room to get in tight docks. With the tandems back you just follow the tires back to where the trailer needs to be.
    The converse is with tandems forward there is overswing you have to be mindful of while tandems back all you have to be mindful of if the trailer itself.
    Either way, you need to Get Out And Look (GOAL) to make sure you are not going to hit anything.
    Neither one is easier all the time. Slide forward when space is limited, slid back when you have the room to eliminate swing worries.

    As for how hard it is to slide, unless the equipment is broken it's simply pulling a lever or pulling a button to unlock the tandems on the way back to open the doors. Should take no more than a second or two.
     
  9. Six9GS

    Six9GS Road Train Member

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    Yes but it requires more distance in front of you. Often you do not have as much distance as to have your tandems all the way back. I think most will agree having the tandems forward to some extent does make it easier. And as for trailer swing out, it's got an exponential quality to it. Meaning the amount of swing out you add from moving tandems forward when they are already close to the rear is alot less than how much is added to your swing out by moving tandems the same amount, but when they are already much farther forward.
    So, you end up with a optimization between the two. Forward enough to make it easier to back in, and back far enough to not create too much swing out.
     
  10. WesternPlains

    WesternPlains Road Train Member

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    You'll find that when your weights are equal on tractor/trailer tandems. The truck drives nicest it can.

    One thing many don't learn at first...
    At times. You will get pins and spring brakes operating partially or not at all when you're going to slide tandems. The answer is to build your pressure to maximum the truck will go. Then dump the air. No, not 110 is good enough in this situation. Maximum and nothing less. (usually 120)
    On the pins. You can get pins that just stick in a slot. Moving forward or back may free them. Otherwise hammer to knock them back works. Many companies trailers do this and the above paragraph. I'm lucky. Have never had to do anything but move the truck a little with the company I'm at now.... Trailers very well maintained.
     
  11. GettingRolling

    GettingRolling Light Load Member

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    Having a rear suspension air pressure guage in the truck is very helpful for estimating weight on the drives. Not super accurate but gets you in the ballpark and makes scaling easier.
     
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