Fifth Wheel Position: Science vs Opinion

  #11  
Old 12-29-2008, 12:27 AM
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I don't think it much matters, the difference would be small.


But I still think I'm right

I'll try to come up with something tonight.
 
  #12  
Old 12-29-2008, 03:36 PM
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as far as smooth ride on the steers... if you have flat spots, or even just bad trailer tires your front can bounce & feel like the prob is in the steers.
 
  #13  
Old 12-30-2008, 01:00 AM
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Truck drivers thinking.... what great entertainment!
 
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  #14  
Old 12-30-2008, 01:42 AM
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Originally Posted by sdloe
Without respect to weight distribution (because this changes the whole topic), I see sliding the fifth wheel forward as far as possible because:

1. Reduces the turn radius, important for us city-delivery drivers.
2. Improves fuel economy (research shows).
3. Here is the opinion vs. science part: By placing more weight on the steers, this places more stress on the front springs thus reducing 'stiffness' and absorbing bounce. Yet so many have the opinion that sliding the fifth wheel back improves ride. What say you? When in a sleeper & loaded heavy, I always slid it forward as much as I could get away with and never had issues with the smoothness. On my present daycab, hauling LTL, sliding forward seems to roughen the ride & bounce more, though the other benefits outwiegh the ride. Opinions?
Chances are, if you are running with the fifth wheel as far forward as possible, you are greatly exceeding the maximum load rating of your steer tires, if not the axle itself. The most common steer tires have a load rating of 6125 pounds, for a total of 12,250 lbs. I run with my fifth wheel one notch forward of center and that puts me around 12,300 loaded and about 11,800 empty with full fuel tanks.

As others have noted here, turning radius refers to how tight of a circle (a full 360 degrees) the TRACTOR is able to make with the steering wheel turned to “lock” one way or another. Fifth wheel position has no bearing on this. It does affect total length of the combination vehicle, but the difference would be negligible as far as maneuverability of the entire vehicle is concerned. You are talking about a difference of perhaps 18 to 24 inches in the total length of a 65 – 70 foot-long (give or take) vehicle so the difference could be as much as two or three percent… not enough IMO to overload your tires or steer axle.

Fuel economy is certainly affected when the gap between the back of the tractor (or end of the cab extenders if you have them) exceeds 36 inches. The shorter the gap, the less the wind resistance will be as it whips around the back of the tractor and impacts the front of the trailer.
 
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Last edited by Musicman; 12-30-2008 at 01:52 AM.
  #15  
Old 12-30-2008, 01:51 AM
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Originally Posted by allan5oh
The wheelbase is considered from the kingpin to the rear tandem.
I guess you MIGHT be technically correct, given the fact that sdloe seems to be talking about the whole combination vehicle, but isn't the term "wheel base" generally applied to the tractor only? I can't recall ever hearing anybody using that term when talking about overall distance between trailer axles and tractor axles or the kingpin. But if we were to apply "wheel base" to the whole combination vehicle, wouldn't we want to measure from the center of the steer axle to the center of the rear trailer tandem?
 
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  #16  
Old 12-30-2008, 02:53 AM
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No, because it's an articulating vehicle.

"wheelbase" for the trailer is kingpin to middle of rear tandem set.
 
  #17  
Old 12-30-2008, 03:14 AM
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Originally Posted by allan5oh
No, because it's an articulating vehicle.

"wheelbase" for the trailer is kingpin to middle of rear tandem set.
I agree, for the trailer, but not the whole combination vehicle.
 
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  #18  
Old 12-30-2008, 10:27 PM
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I set my fifth wheel dead center about three yrs ago and haven't moved it since with no problems to speak of. I keep decent rubber on both tractor and trailer. I have no weight issues that can't be resolved by sliding the trl tadems. Good smooth ride ( as smooth as it gets )on 05 fl columbia.
 

Last edited by can-do; 12-30-2008 at 10:31 PM.
  #19  
Old 01-16-2009, 06:05 PM
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Originally Posted by allan5oh
No, because it's an articulating vehicle.

"wheelbase" for the trailer is kingpin to middle of rear tandem set.
Actually, "wheelbase' is measured between pivot points, which for a tractor would be from front spindle to the centerpoint between the rear tandoms which is where the rear pivots.

Lngtaltxn
 
  #20  
Old 01-26-2009, 11:24 PM
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i got mine set in the center, seems to ride the best there with the leaf spring trailer behind it. plus i store vee boards on the catwalk so i make sure i have enough swing to clear them.
 



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