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  #1  
Old 06-19-2007, 04:29 AM
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Default How many holes to slide the fifth wheel formula?

My trainer taught me a formula to slide the tandems that has worked every time so far.

It goes like this
(higher weight - lower weight = sum) /2) /350 = number of holes to move tandems.

example: drives=34500 lbs tandems=29300 lbs
34500-29300=5200
5200/2=2600
2600/350lbs=7.4
move tandems 7 holes
[if # to right of decimal is 6 or higher round up a hole, 7.6 will need to move 8 holes ]
So far this has worked well for me.

Today my weights were steers, 11660; drives, 25420 and tandems, 19800. I thought I am good to go, and so I went down the road. Well the truck just felt "weird" so i stopped and moved the fifth wheel back 4 holes and it now feels normal again.

After all that my question is, is there a formula for sliding the fifth wheel? Or take an educated guess and go back for a reweigh.

Thanks,
Dan Isa Wannabe
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  #2  
Old 06-19-2007, 07:55 AM
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I like your formula for the weight issue but since I am no good at math I would just do.....34,500 on the drives...move it three or four holes and call it good. I figure usually 300 per hole. I dont (especally since I'm unemployed right now) hardly ever slide my fifth wheel if I dont have to, I keep it centered between the two drive tires which has worked for me. Make sure when sliding it forward that you have enough clearance between your mudflap/frame and the landing gear as not all trailers are the same. I have heard people say about 250 lbs per hole on the fifth wheel
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  #3  
Old 06-19-2007, 11:50 AM
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Quote:
Originally Posted by Rockee
I like your formula for the weight issue but since I am no good at math I would just do.....34,500 on the drives...move it three or four holes and call it good. I figure usually 300 per hole. I dont (especally since I'm unemployed right now) hardly ever slide my fifth wheel if I dont have to, I keep it centered between the two drive tires which has worked for me. Make sure when sliding it forward that you have enough clearance between your mudflap/frame and the landing gear as not all trailers are the same. I have heard people say about 250 lbs per hole on the fifth wheel
I'll have to dissagree on this one guys, Fifith wheels move between 5 hundred to 8 hundred per "hole" and it only mainly effect the steering axle weights the drive axles. By pushing weight on to the steer axles it "might" give you some room to add a little to the tandems, but when it gets that close to being overweight or over bridge, you probably will out of luck.

So set the bridge, set the fifthwheel and if the load is too heavy, have them rework that by moving freight forward, or removing cases off of the load.

did you check your axles weights AFTER you slid up to twelve hundred pounds off the steering axles to the drives, This is potentially fatal moving that much weight off of the steering axles. In my opinion,you should have done nothing to this as everything was legal and decently spread out.. if you HAD to do something, maybe slide the tandems up a little to take a small amount of weight from the drives.
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Old 06-19-2007, 03:38 PM
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I think almost every different driver will give a different answer on this....alot of it just plain flat out depends on how the truck is load....location of the weight in the trailer makes a big difference when sliding tandems and fifth wheels
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  #5  
Old 06-19-2007, 04:57 PM
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I cant disagree with you Fozzy but now I can say "I have heard people say between 250 and 800 per hole on the fifth wheel". In my driving career its been almost a non issue with me so I just "set it and forget it"
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  #6  
Old 06-19-2007, 08:30 PM
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Regardless of the 5th wheel or trailer tandems, how the weight of the load is distributed in the trailer will effect how much weight is moved per "hole".

Also how the "holes" are spaced will greatly effect how much weight is moved per notch.

Trailers with small holes spaced close together generally move between 200-300 pounds per space, and these seem to be the most common slide arrangement today.

If you have a trailer with very large holes the you are gonna be moving 400-500 lbs per slot.

Same goes on the 5th wheel. The slides with the notches will move less per unit than the ones with the bigger holes that have a "bar" in them to lock it down.

When it comes to figuring weight I applied a "KISS" principle.

Trailer with the small holes I used 250 lbs per hole. Took the axle weight minus 34,000 divided by 250.

For the 5th wheel I used 500 lbs and the forumla of weight of overloaded axle (steer or drive) minus the legal weight divide by 500.

Rarely did I ever have to do a second slide on either.

In the rare event a second move after the re-weigh was called for then I would figure out exactly how much weight was moved per hole and figure out how much to slide.

As far as the 5th wheel goes, if you keep it pretty well centered over the drives on most trucks it is rare for you ever need to adjust it. In 6-7 years I think I only had to move mine twice.
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  #7  
Old 06-20-2007, 01:08 AM
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Fozzy & Uturn make some great points about moving the 5th wheel....

1. Load the trailer as best as you can (shipper's help can either be brilliant or utterly stupid when it comes to this).
2. Slide the tandems.
3. Slide the 5th wheel (on rare occassions).
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  #8  
Old 06-20-2007, 03:31 AM
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First of all, thanks to all who replied Good info to keep in mind from all.

Quote:
Originally Posted by Fozzy
I'll have to dissagree on this one guys, Fifith wheels move between 5 hundred to 8 hundred per "hole" and it only mainly effect the steering axle weights the drive axles. By pushing weight on to the steer axles it "might" give you some room to add a little to the tandems, but when it gets that close to being overweight or over bridge, you probably will out of luck.

So set the bridge, set the fifthwheel and if the load is too heavy, have them rework that by moving freight forward, or removing cases off of the load.

did you check your axles weights AFTER you slid up to twelve hundred pounds off the steering axles to the drives, This is potentially fatal moving that much weight off of the steering axles. In my opinion,you should have done nothing to this as everything was legal and decently spread out.. if you HAD to do something, maybe slide the tandems up a little to take a small amount of weight from the drives.
Hi Fozzy. About checking the weight after taking so much off the steers, help me understand what the issue may be. I was at 11660 on the steers, 25420 on the drives and 19800 on the tandems. The fifth wheel was all the way forward and I moved it back 4 holes. I hav'nt reweighed yet but maybe I will just to see what the effect was. My guesstimate for the current setup is about 10200 on the steers and 26500 on the drives. When I slid it to the front, it changed about 600lbs per hole, cargo weight was 44400lbs, this load it is 21012lbs.

That word "fatal" has me concerned and I'd like to hear more about this. Oh Yea, I'd also like to live. BTW, after the move the "funny" feeling left the truck and I went through the scale house in AR, I40, MM280ish and got the green light to keep going.

Uturn2001, thanks, I think you put the important points together in a nice list. When I get home I'll print it out and tape it to my clipboard for future reference.

Again, thanks to everyone, all of you are a big help.

Dan
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  #9  
Old 06-20-2007, 03:56 AM
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Quote:
Originally Posted by Danisawannabe
...That word "fatal" has me concerned and I'd like to hear more about this....
Not sure what "fatal" meant to Fozzy but here's my take....

Ever experience the feeling of turning the steering wheel in a car while its snowing and the steering doesn't respond? In other words you turn the wheel but the vehicle continues to go straight?

Something similar can happen when you combine more speed along with less weight on the steer tires (having the 5th wheel all the way forward towards the steering axle). Say you're rounding a gradual turn doing 65MPH and hit a major bump. The bump could cause you to careen towards the shoulder. You compensate the other way but the steering is loosey-goosey because you don't have enough weight on the front axle. In seconds you find yourself oversteering first one way and then the other to compensate for the lack of steering response....

So...having the 5th wheel centered over the drive axles is a good way to go most of the time....
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  #10  
Old 06-20-2007, 04:27 AM
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Quote:
Originally Posted by BigWheels
[snip]
Something similar can happen when you combine more speed along with less weight on the steer tires (having the 5th wheel all the way forward towards the steering axle).
[snip]
I might not understand correctly, but doesn't "having the 5th wheel all the way forward towards the steering axle" put as much weight as possible on the steering axle?

Dan
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