bfast54
Traverse City ,Mi.
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Funny, I was thinking the same thing, about...............
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SoCalDesertRider
SanDiego, CA, USA
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The front axle of that truck is very capable of holding up all the weight on it whether a trailer is hooked up or not. Trying to take weight off the front axle is not necessary.
The reason to put the trailer pin behind the rear axle is to put more weight on the rear axle and hopefully soften the ride for the trailer, since the truck is made to carry alot more weight than an RV trailer can apply to it, so it rides rough with the light pin weight of the RV trailer.
Or, you can use an air ride hitch and air ride suspension to soften the ride and put the trailer pin over the axle in the usual position.
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RoyJ
Vancouver, BC
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Engineer9860 wrote:I guess my experiences come from 1,000,000mi driving class 8s OTR. My guess is that I have driven more miles in a class 8 than almost anybody here, and believe me, you want that pivot point over the axle, and weight transfer has little to do with why.
Even with the fifth wheel set over the rear axle (split between the two on a tandem) it is possible to get the front axle to hop (like riding waves in a boat) on a class 8.
GEEZ but then again what do I know, I only have experience on my side.
On second thought.........Ignore my posts, forget that I posted in this thread, do what ever you want, I'll do what I want, and don't come crying to me when it all goes wrong, because I'll have no sympathy. 
You people REALLY have nothing to do if it is time to argue about 5th wheel location.
To the O.P........ I still think you have a cool set up. 
There's a HUGE difference between towing a 65,000 lbs trailer with 50% of its weight on the pin (32,500 lbs), than a 20,000 lbs 5th wheel with 25% of its weight on the pin (5,000).
I've seen many singled bobtailing tractors close to GAWR in the front. With a 15,000 tractor, this means roughly 12,000 lbs in the front and 3,000 in the back, in the worst case. A front heavy Volvo with full tanks will be very close to that ratio.
Simple physics would tell you that's not good. I would definitely agree with the others and put the pin as far back as possible to achieve atleast a 50%/50% distribution with the trailer hitched up.
Just think, in commercial applications you have 23%/77% weight distribution, given a 12k front and 40k rears.
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SoCalDesertRider
SanDiego, CA, USA
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32,000 for tandem rears, 16,000 for single rear.
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donn0128
Pronounced Ore-gun
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Now Now boys, play nice or else we will have to take your toys away from you!!
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BruceStarkey
Ontario, Canada
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RoyJ: You nailed it! On average, these class 8's when converted are configured with the hitch 3 feet or more behind the axle center line. On average, they are also set up with an air bladder hitch most commonly the Trailersaver with 2 bags and sometimes the 3rd bag (7,000lb pin-weight) as well as ballast weight added behind the axle just in front of the hitch. The other route becoming more popular, is to configure the toter bed from welded plate steel with the rear vertical "bumper" plate being of 1/2" thickness to add weight at the furthest rear point available. The engineering that has gone into these units is sound with more than a couple of the fellows being professional mechanical engineers with one of them designing (patent applied for) a hitch with 4 air bags and 4 parallel link arms rated for over 30,000lbs that is designed to fit low between the frame rail extensions as far behind the rear axle as you can get.
The most common/popular tractor selected for these conversions are Pete 387, Kenworth T2000's and the Volvos of 610, 660, and even the 770 sleeper versions. The latter two are notoriously heavy right from the factory on their front ends so all of the weight you can unload from that axle will only benefit the handling/ride/safety especially when bobtail. The first attempts involved moving the heavy commercial Holland heads rearward to improve weight bias but as those hitches had minimal side axis tilt capabilities which put enormous stress on RV kingpins, most opt to remove the commercial hitch and add ballast to compensate.
Not to denigrate anyone's OTR experience, but configuring, one of these babies for RV usage is approached using a completely different set of engineering principals.
P.S. On edit, Perhaps it would help to explain that the truck pictured in my sig is a class 6 and with full fuel and typically loaded with Harley aboard is well over 17,000lbs without the trailer. With the trailer of 3,400lbs pin weight on my hitch that is 14" behind axle the ride only improves without any sign of front end "hopping"!
* This post was
edited 07/09/08 07:08pm by BruceStarkey *
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