How far to slide tandems?

Nope..nothing to do with the 5th wheel...try again!

Remember I said every truck is different> FUEL WEIGHT DISPLACEMENT 1st clue

 

Fuel is a lighter than water, hence why they use desil to lift boats from water. I know water weighs 8 pounds a gallon, fuel 7 pounds a gallon.

I use 7.5 pound per gallon when figuring out how much the fuel will put on the steers. For the most part always scale full of fuel, unless you are at a shipper with a scales. When I fuel I have found that fuel adds about 5.75 pounds to my steers per gallon. That is on the cascadia. Not good enough at math to figure out a formula for it, I have alway just added the total weight of fuel to steers. Never had a problem.

If I have been slightly over on steers, I just run out enough fuel to be legal and dont fill past that point, dont waste your time sliding fifth wheel. Fueling is much easier than messing with 5th wheel.

 

Nope, getting closer but not there yet...% of weight to drives and % of weight to steers, and why would it matter? There is an easy way to figure it out!

I used to have fun with this with my students, some the game lasted all 6 weeks, others had it in the first. But it is useful knowledge!

 

Well doing the math I have notice accidently I'll take a guess at about 75% to steers 25% to drives. maybe little higher.

Taking a shot in the dark LOL. If I were better at math I wouldn't be drivin' a truck Heh heh

 

Its a pretty simple physics problem...

For figuring what fuel does to steers/drives - consider the drives to be just one combined point that will be loaded by the fuel weight. Then, just split it 50-50 between the steers and the drives.

As far as the fifth wheel is concerned, I've adjusted mine to a point that I can put full fuel on with a 45000 lb load, and still be legal (under 12000) on the steers. That's where it stays - a little behind the front drive axle - works for my combination of tractor/trailer and load... your stuff will probably be different. I've only messed with it once on a very nose-heavy trailer from the jerks at Nestle in Springvale UT - those a-holes refused to adjust the load, and I was too tired to argue.

When I adjust my tandems, I take a first approximation by sight to where I think they ought to be set. Then get a weight from the scales, and use the following...

number of holes to slide tandems =

(tandem wt - drive wt)/(2 * adjustment wt per hole)

That will give you a decimal; negative means slide forward, positive slide rearward. It's most accurate when you're within say 5 holes of where you want to end up.

So...

Lets say you figure your trailer adjusts about 380 lbs per hole, your trailer is in the 10th hole when you weigh, and your scale ticket says:

Steers: 11380
Drives: 34340
Tandems: 30880

No. of holes to slide = (30880 - 34340)/(2 * 380) = -3460/760 = -4.552631578

So your tandems need to come forward about 4.55 holes, or...

10-4.55 = 5.45

I like to run a little heavier on the drives than the tandems so you wouldn't want to go to the 4th hole... put it in the 5th.

You can figure the number of pounds per hole by playing with the numbers after you reweigh a few times. I've gone back and forth a bit, but for the new Wabash's we pull, 380 pounds per hole works for me. It was a bit over 400 for the older Great Danes - but it's going to vary depending on the equipment you run.

A final note... Disclaimer for the naysayers: This works for me - your mileage may vary. I rarely bother to get a reweigh since I started using this, and I don't get overweight violations. Try it!

 

Whoa baby..just got a headache trying to figure that out...a bit on the overdone it maybe. Let me try on a simpler method..

using your weights: ST= 11380, DR=34340, and TN=30880

using the given in this thread of 350 lbs per hole; you need to move at least 340 lbs to be legal (34,000) on the drives, but as you said it is better to be heavy forward (drives to tandems) but better still to be as close to balanced as possible.

To get balanced we need to move ( 34340+30880=65220..divide by 2=32600) 34340-32600=1740, 1740 divided by 350=approx 5 (1750), so if we slide 5 holes (weight forward=tandems back / weight back=tandems forward) in this case forward 5 holes...should make the drives 32590 and the tandems 32630...balanced like a goodyear tire out of the Big-O shop! Not a perfect balance but 40 lbs won't make a difference, plus we have not figured in fuel weight full or partial tanks, and where the fuel weight will go.

But what happened to the steers? Did they lighten up or get heavier. In this case it wouldn't matter since we know the limit is 12,500 for steers. There would be no way to get 1100+ lbs transferred to the steers in this scenario.

Your first line says "split it 50-50 between the two axles". Which two axles; the steer axle and the forward drive, or the two drive axles...flaw in your theory, (there are 3 axles on most tractors) and math a bit over the top for me, but if it works for you, fine.

Now the question was; How do you figure the fuel weight displacement between the steers and the drives, and why does it matter? you didn't answer the question. Good try though!

 

Just treat the steers as a point in contact with the ground, and both drive axles as a point in contact with the ground... that's how we weigh them anyway...

Can you tell I grew up in an engineering camp??? Heh! The formula just compare half of the difference between the drives and the tandems to whatever you figure the adjustment per hole is. Just puts it in a format that's easy to plug into a calculator, that's all.

 

Good political non-answer..don't give up so easy..the answer is very simple really!

 

Another thing that is not mentioned here is "long loads" as in 60' pipe or beams.
For you drivers that think you can "set it and forget it" that's fine if all you haul is one commodity and nothing that overhangs your trailer.
60' pipe or beams even on my tractor, which has a wheelbase of 265", I still have to slide the fifth wheel all the way back. Then the load can only over hang 10' 2" or less off the tail. Otherwise, no running after sunset in most states unless you have load lights, and permits even for CA which will let you run up to 75' rig+load. I usually go with 10' on the tail and 2' on the front. If you don't slide the fifth wheel...well don't make any turns greater than 45 degrees unless you like changing out pogo-sticks or worse....lines.

 

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Helloooooooo !!!

Come on guys, it's sliding tandems. Not advanced Calculus.

Ya'll are scaring half the newbs to death.