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Car Forum / Dodge / Dodge Trucks / July 20055th Wheel Hich Position?
A fifth-wheel trailer is one that has a hitch that connects to the towing vehicle at a point above the rear axle of the towing vehicle - not at a point on the rear of the vehicle as with a pull-behind trailer. For example, this is a 5th wheel: http://www.theironworker.com/Fifth%20Wheel%20Trailer.jpg My question concerns position of the point of attachment, let's say, the position of the king pin. For normal pulling of the trailer, where is the best point to have the king pin? Should it be directly over the axle of the towing vehicle or should it be ahead of the axle? If ahead, by how much? In what ways does handling change if the position of the king pin is changed? This page http://www.etrailer.com/faq/fifthwheelfaq.asp discusses using a slider arrangement to move the king pin for maneuverability. It doesn' t discuss the optimum position for towing. Instructions that came with a hitch say to mount 0 to 6 inches ahead of the axle, but provides no further information. |||||||||||||||| Nehmo Sergheyev |||||||||||||||| >A fifth-wheel trailer is one that has a hitch that connects to the > towing vehicle at a point above the rear axle of the towing vehicle - [quoted text clipped - 8 lines] > how much? In what ways does handling change if the position of the king > pin is changed? Each truck's manufacturer has their own specifications as to the proper location. Many say to position the center 2" - 4" forward of the rear axle while others specify a position directly over the axle. You may wish to peruse the installation instructions on the Reese website for hitch rails similar to the ones you are interested in on the make and model truck that you have. http://www.reeseprod.com/support/support/su_install.shtml#5thwheel will take you directly to their support page. The reason for the placement of the hitch centerpoint above or very slightly ahead of the rear axle is to allow that portion of the weight of the trailer that rests upon the hitch to be transferred to the rear axle without disturbing the balance of the truck. If the point of weight transfer falls behind the rear axle then the front (steering!) wheels are levered upwards with a corresponding reduction in vehicle control. Doing a wheelie down the highway while pulling a trailer will attract LOTS of unwelcome attention! <G> > This page http://www.etrailer.com/faq/fifthwheelfaq.asp discusses using > a slider arrangement to move the king pin for maneuverability. It doesn' > t discuss the optimum position for towing. The sliding hitch mount is intended to provide adequate clearance, during tight turns, between the rear of the cab and the front of the trailer when a short (6' or less bed) wheelbase truck is used as a tow vehicle. > Instructions that came with a hitch say to mount 0 to 6 inches ahead of > the axle, but provides no further information. > > |||||||||||||||| Nehmo Sergheyev |||||||||||||||| >>A fifth-wheel trailer is one that has a hitch that connects to the >>towing vehicle at a point above the rear axle of the towing vehicle - [quoted text clipped - 44 lines] > > I would think that the weight of the engine would be one of the considering factors for hitch location. Such as the Ram hitch is over the axle, but my 94 GMC with a 350 gas engine is 3" forward. Both trucks are almost the same length and wheel base. The Ram clearance is 37" (pin to cab) but the 5th wheel is quite a bit wider. I do not know what the turn angle is, but it will be far less than 90deg. I might consider on installing a slider so I can gain cab clearance of a couple of inches at 90deg, that would be aproximately 11" plus the desired clearance. My rig is 96" wide, pin location is aproximately 1" forward of front cap. I know the Cumins engine is heavy but I dont think I would consider runnig down the road with the pin slid back. Any suggestions?  SignatureBILL P. 2004, 2500 SLT Quad Cab, Dodge Ram, SLT, SWB, 2WD, 5.9 HO Turbo Diesel, 48RE Auto Trans, Anti-Spin 3.73 Dif.Rhino Liner, Husky 16K. Voyager Controller 2005, 27RL Wildcat, DT/PC Wi-Fi. Dual EU2000i Hondas Just Me and Dog <snip> >I would think that the weight of the engine would be one of the >considering factors for hitch location. Such as the Ram hitch is over [quoted text clipped - 10 lines] > >Any suggestions? hey Wild Bill... how ya been?? We decided not to get a fiver, but researched them for quite awhile... most folks said that the extra $100 or so for the sliding hitch was "cheap insurance" for when they had a tight spot to get in or out of... Most had never needed it, but used it a few times to see how it worked.. A lot depends on the truck config.... the longer the bed, the less chance of needing one, etc... mac Please remove splinters before emailing > <snip> > [quoted text clipped - 14 lines] > > hey Wild Bill... how ya been?? Life is great how is it with you? > We decided not to get a fiver, but researched them for quite awhile... most > folks said that the extra $100 or so for the sliding hitch was "cheap insurance" [quoted text clipped - 3 lines] > A lot depends on the truck config.... the longer the bed, the less chance of > needing one, etc... Mac, you are correct here, but I got what I got and it would be cheaper to get the hitch slider than a new truck, and I would hope that I would be like the rest of them and not need it. > mac > > Please remove splinters before emailing SignatureBILL P. 2004, 2500 SLT Quad Cab, Dodge Ram, SLT, SWB, 2WD, 5.9 HO Turbo Diesel, 48RE Auto Trans, Anti-Spin 3.73 Dif.Rhino Liner, Husky 16K. Voyager Controller 2005, 27RL Wildcat, DT/PC Wi-Fi. Dual EU2000i Hondas Just Me and Dog <snip> >Life is great how is it with you? We're doing really well.. no major illness, still married, getting ready for an rv trip to the delta today.. (Delta Bay) >Mac, you are correct here, but I got what I got and it would be cheaper >to get the hitch slider than a new truck, and I would hope that I would >be like the rest of them and not need it. Well, we all know that the longer the wheel base, the better the TV is supposed to be... The trade off is that if you get a 2500 or 3500 quad cab with long bed, you need some place to park it.. *g* Our rv buddies with an f250 4 door and 36' fiver are semi-full time, and have only needed to slide the hitch back once... he figured that he could get it out without sliding, but it was going to take a lot of cutting back and forth to get around the lug nut that pulled in across from him during the night and left his trailer hitched with the truck sticking out in the street.. mac Please remove splinters before emailing Greetings, Different vehicle manufacturers (as well as the hitch manufacturers) will have varying recommendations. You are going to have to read your owner's manual as well as the help and installation pages from the hitch manufacturer's web sites for the best information for the set-up you have. As for handling, the farther forward the king pin is in front of the rear axle, the more weight is transfered forward to the front wheels. Admittedly 6" may not sound like a whole lot, but the only way to determine what feels best to you when towing your particular combination is trial and error, which is much easier with a sliding set-up.. A change of an inch or two could make your steering feel heavier or lighter, or give you too much rear end "squirm". If you go to a newsgroup like alt.rv I can almost guarantee that the folks there will have more than a few things to say about this! Depending on the length of the bed it most likely effect your turning radius as well. This is especially important with a short-bed truck. The last thing you want is to have the front corner of the trailer crush your back window and back edge of your roof while you are taking a tight turn. This is why you see so many forward-offset kingpin setups on the larger 5th wheel trailers these days. Cheers - Jonathan >A fifth-wheel trailer is one that has a hitch that connects to the > towing vehicle at a point above the rear axle of the towing vehicle - [quoted text clipped - 17 lines] > > |||||||||||||||| Nehmo Sergheyev |||||||||||||||| [This is a repeat of the original post so that I can add news:alt.rv .] A fifth-wheel trailer is one that has a hitch that connects to the towing vehicle at a point above the rear axle of the towing vehicle - not at a point on the rear of the vehicle as with a pull-behind trailer. For example, this is a 5th wheel: http://www.theironworker.com/F ifth%20Wheel%20Trailer.jpg My question concerns position of the point of attachment, let's say, the position of the king pin. For normal pulling of a trailer, where is the best point to have the king pin? Should it be directly over the axle of the towing vehicle or should it be ahead of the axle? If ahead, by how much? In what ways does handling change if the position of the king pin is changed? This page http://www.etrailer.com/faq/fi fthwheelfaq.asp discusses using a slider arrangement to move the king pin for maneuverability. It doesn't discuss the optimum position for towing. Instructions that came with a hitch say to mount from 0 to 6 inches ahead of the axle, but provides no further information. [crossposted: news:alt.autos.dodge.trucks news:alt.trucks.chevy news:alt.trucks.ford news:rec.crafts.metalworking news:alt.rv ] |||||||||||||||| Nehmo Sergheyev |||||||||||||||| My hitch is directly over the rear axle. Vehicle is a '99 F350 CC 4x4 8' bed. Hitch weight is 2300 lbs. Handling is transparent. With the 5th wheel attached, the truck is level. 5th wheel axles have been reversed to match the truck. : A fifth-wheel trailer is one that has a hitch that connects to the : towing vehicle at a point above the rear axle of the towing vehicle - [quoted text clipped - 17 lines] : : |||||||||||||||| Nehmo Sergheyev |||||||||||||||| I towed a 30' fifth wheel with a RAM 2500 with an 8' bed for ten years. The hitch was positioned so that the king pin was directly over the rear axle and the handling was great. The trailer weight was ~8,000 lbs. SignaturePcolaPhil To <Reply> Remove -SPAMNOT- 24 hours in a day ... 24 beers in a case...coincidence? |A fifth-wheel trailer is one that has a hitch that connects to the | towing vehicle at a point above the rear axle of the towing vehicle - [quoted text clipped - 17 lines] | ||||||||||||||||| Nehmo Sergheyev |||||||||||||||| There is a formula which can be used to accurately calculate the position of the fifth wheel, but you need to have a few details about the trailer and tow vehicle. You need to know how much weight is transferred onto the fifth wheel when laden by the trailer. You need to know the unladen weight of the towing vehicle and the unladen weight on each axle. You also need to know the maximum weight allowed on each axle. You need to know the wheelbase of the towing vehicle. Loadbase is the distance from the fifth wheel to the front axle The formula is weight transferred onto front axle = (wheelbase / loadbase)* weight transferred onto the fifth wheel You can the play around with the "loadbase" number to achieve the optimum weight distribution onto the front and rear axles. Ideally you want to have weight transferred onto the front and rear axles in the same ratio as the manufacturer's maximum gross weights. eg max weight on steer of 3 tonnes and 6 tonnes on the rear indicates a 1:2 ratio. We used extensions of this basic formula to achieve maximum loading on B Double fuel tankers with 8 compartments with varying fuel density to ensure we max loaded to legal limts every load. If you use pounds then use inches, if you use kilogrammes use centimetres. Dont mix your avoirdupois with your metrics. > A fifth-wheel trailer is one that has a hitch that connects to the > towing vehicle at a point above the rear axle of the towing vehicle - [quoted text clipped - 18 lines] > -- > |||||||||||||||| Nehmo Sergheyev |||||||||||||||| - Nehmo - Fifth wheel load = The point load the tongue of the 5th wheel trailer places on the frame of the towing vehicle while the vehicle and trailer are attached to each other and at rest. For the moment, leave aside the best place in terms of carrying fifth wheel load. Is there any advantage one way or another for position of the fifth wheel load in terms of steering or maneuverability. Those with the fifth wheel load placed directly over the rear axle speak approvingly of that position in terms of maneuverability. - Roger & Lorraine Martin - > There is a formula which can be used to accurately calculate > the position of the fifth wheel, but you need to have a few [quoted text clipped - 31 lines] > If you use pounds then use inches, if you use kilogrammes > use centimetres. Dont mix your avoirdupois with your metrics. -Nehmo - > > A fifth-wheel trailer is one that has a hitch that connects to the > > towing vehicle at a point above the rear axle of the towing vehicle - [quoted text clipped - 15 lines] > > Instructions that came with a hitch say to mount 0 to 6 inches ahead of > > the axle, but provides no further information. |||||||||||||||| Nehmo Sergheyev |||||||||||||||| > - Nehmo - > Fifth wheel load = The point load the tongue of the 5th wheel trailer [quoted text clipped - 77 lines] > > |||||||||||||||| Nehmo Sergheyev |||||||||||||||| > Those with the fifth wheel load placed directly over the rear axle speak > approvingly of that position in terms of maneuverability. You may find your steering is light at low speeds - but not something that is desireable at higher speeds. In fact downright dangerous in some situations. Heavy braking will cause the vehicle to lose steering as the vehicle will tend to lift its front axle if the fifth wheel is over or behind the rear axle. Common cause of jack knifing a semi trailer is to have insufficient weight transferred onto the tow vehicle steer axle, you can induce a power jack knife by just putting your foot down too hard on the accelerator. And on and on. There's plenty more reasons not to fiddle about with fifth wheel formulae. >> Those with the fifth wheel load placed directly over the rear axle speak >> approvingly of that position in terms of maneuverability. [quoted text clipped - 9 lines] > down too hard on the accelerator. And on and on. There's plenty > more reasons not to fiddle about with fifth wheel formulae. Can you, then, explain why the instructions from Dodge for my 2003 Dodge RAM 3500 specifically states that the hitch be centered precisely over the centerline of the rear axle? FWIW, I've *never* encountered any lightening of the front end when *slowing* while towing my 14,100# 5er. Hint: the leverage upon the frame that results from the vertical "arm" of the hitch support forces the front end *down* during deceleration. > Can you, then, explain why the instructions from Dodge for my 2003 Dodge RAM > 3500 specifically states that the hitch be centered precisely over the [quoted text clipped - 5 lines] > Hint: the leverage upon the frame that results from the vertical "arm" of > the hitch support forces the front end *down* during deceleration. As a former long haul driver, side lined by MS, I'll make some comments here. In your case you got a truck whose manufacturer has decided the optimum position for your model is over the center line. And that is assuming you load the trailer balanced. with the correct "tongue" weight for lack of a better word right now. The real test is the same we use with big rigs, scale the axles. Know what the front weight is empty, and the rear axle. If you hook up and the front gains little, or worse, loses weight, the king pin is too far back, or the load is way out of balance. As for lightening of the front axle, move the pin behind the axle, and have good brakes on the trailer and the front end will get light. Same thing can happen on a single screw tractor if the fifth wheel is slide back to far, especially if the axles on the trailer are slide to far back. A little harder to have happen on a twin screw because the pin never slides beyond the rear axle, most of the time wont even slide back over the rear axle. Whitelightning >> Can you, then, explain why the instructions from Dodge for my 2003 Dodge > RAM [quoted text clipped - 21 lines] > loses weight, the king pin is too far back, or the load is way out of > balance. He who fails to weigh is way too careless to be entrusted with a vehicle towing. > As for lightening of the front axle, move the pin behind the axle, and > have [quoted text clipped - 10 lines] > even slide back over the rear axle. > Whitelightning Sliding RV-type fifth-wheels are not intended to be slid back while towing - only for tight space manuevering - and are not needed for a truck with an 8' bed. You might wish to re-read my earlier post in this thread. <G> > Sliding RV-type fifth-wheels are not intended to be slid back while towing - > only for tight space manuevering - and are not needed for a truck with an 8' > bed. Starting with the original post nehmo asked where to mount. Then you follow up later with "Can you, then, explain why the instructions from Dodge for my 2003 Dodge RAM 3500 specifically states that the hitch be centered precisely over the centerline of the rear axle?" I gave you examples I have personally experienced and or witnesses with over 1.5 million miles pulling fifth wheel mounted trailers, mostly big rigs, some hot shots (22 to 40 foot flatbed behind 1 ton dually) but the principals are still the same. In looking at the lower brands of hitches such as Reese, draw tight etc,then you are correct,the hitch is not designed to be used slid. Buy a high quality hitch such as a fontain, or highjacker to name but two,and they have hitches designed to tow slid as needed. You rv may be fine in one position every time, But tom,dick or harry may pull a flat bed, or a goose neck or some other configuration and need the hitch to move according to the load. The balance may be very different pulling a John Deere with a back blade and bucket loader all week then when the rv is on for the weekend. The only way to know for sure is scale the rig empty and loaded and compare front axle weights adjust the pin location as needed. Given how much a truck costs,and how little the difference in hitch prices are unless we get into air ride hitches, why limit the trucks abilities with a fixed hitch in the first place. Whitelightning >> Sliding RV-type fifth-wheels are not intended to be slid back while > towing - [quoted text clipped - 3 lines] > > Starting with the original post nehmo asked where to mount. I then gave him a link to mounting instructions for the type of hitch, and truck, about which he'd asked. > Then you follow up later with > "Can you, then, explain why the instructions from Dodge for my 2003 Dodge [quoted text clipped - 30 lines] > > Whitelightning First off - a fifth-wheel hitch is unlikely to be used for hauling heavy equipment. [A friend of mine DOES do this but he's an exception] That kind of hauling is normally done with a gooseneck hitch - which uses a fixed ball in the bed of the truck and a cylindrical tube-with-locking-jaws on the trailer. Sliding fifth-wheel hitches [goosenecks are *all* fixed-position] are used in short-bed trucks to enable tight turning when, without one, the trailer would impact some part of the cab. When towing, the sliding mechanism is returned to the "locked" mode at the point over (or slightly in front of) the rear axle. The examples that you provided of the use of an adjustable-position hitch do not apply in this type of towing or with this type of hitch. In fact, it would be most difficult to mount one in a Class 1 - Class 3 truck without dismounting the bed, much less actually USING the feature. <G> Don't forget that the "balance" of non-OTR trailers is such that there is far less weight placed on the hitch - and, thus - the truck than with a trailer with axles at the very rear. BTW, I *do* use an air-suspension hitch - and love it. <G> I wouldn't consider the tractor I exampled heavy equipment, or even medium duty equipment for that matter, and many small landscape and lawn companies down here in Florida use 1 ton dually with a sliding fifth wheel and a gooseneck adapter to haul their various trailers. John Deere 210LE. Or a Bob Cat., or any number of mini track hoes being used these days. Unfortunately I have seen some fools pulling small front end loaders like a the idiot pulling an old cat 910 two weeks ago up I-95 on a similar set up.Memory says the 910 weighed about 18,000 lbs. and the ford 350 pulling it was riding real high in the nose. http://www.hijacker.com look at the top picture and you will see the hitch I refer to from hijacker, a 24 SPL-21 slider. something they are not clear on the web page but if you call you find out it can be done is the receiver can be swapped between mounts so you can convert from fifth wheel to gooseneck if you don't like using a gooseneck adaptor. They also offer a conversion set up, the 24 Uk-21 allows kicking the above hitch back for maneuvering room with out dropping the landing legs, unlocking the slider, moving it, relocking and lifting the legs, in the rear position it is not designed to tow, but the main body can be slide to move the load point as needed to balance the load. The down side with Hijacker is no air hitch, but there are a few out fits that offer a conversion. I do a little side work shuffling cars between auctions and dealerships and the guy I run for uses 1 ton dually trucks. Two have the above hitch, 1 has a fontain. Because you cant always load the trailer for perfect weight, because of the shape of the vehicles hauled, sliding the hitch is the only way to get it balanced. He also pulls a 37 foot Carriage behind one of them with a Hijacker. The car trailers will carry three vehicles, one in a drop deck location, and two on top. get a van on the back, and two cars and the fifth gets slide foreword. Cant put the van on top first because of clearance problems height wise, and it gets top heavy, pain to load because you have to drop the trailer to get a car in the drop deck area. By no means a long haul set up, least wise I wouldn't want to. good for short runs tho, and helps pay the bills. Also pull a 2003 36 foot fifth wheel SuperHauler Race car trailer by United behind it.(guy has way too much money and too many toys) Conversation getting interesting, and its nice not seeing any flaming contest, just frank opinions being traded.. Whitelightning > In your case you got a truck whose manufacturer has decided the optimum > position > for your model is over the center line. Not the TRUCK manufacturer - it's the decision of the HITCH manufacturer. My Hijacker is 3" in front of the axle. Cheers, Joe >> In your case you got a truck whose manufacturer has decided the optimum >> position [quoted text clipped - 5 lines] > > Cheers, Joe In the case of my 2003.5 Dodge and EasyRider hitch it's by mutual agreement: the hitch MFG sez to put it where Dodge sez to put it and Dodge sez to put it precisely over the centerline of the rear axle. You'll find that most pickup manufacturers publish a Technical Service Bulletin that specifies the exact placement and mounting methods. |
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