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Open Roads Forum  >  Fifth-Wheels

 > 40 ft. 5th Wheel Turning Radius?

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Francesca Knowles

Port Hadlock, Washington

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Posted: 01/19/12 02:37pm Link  |  Print  |  Notify Moderator

At Semi turning radius there's a formula for calculating this number for 18-wheelers,...

Here's the image from the site showing an approximately 40 ft trailer with a tractor I believe to be about the length of a 40 ft. 5th wheel's TV.:

[image]

Does the formula at the site hold true for a 40 ft. 5th wheel RV, despite the more forward placement of the RV's wheels?

And if not, how is the radius affected, that is, is more or less room required?

Thanks!


" Not every mind that wanders is lost. " With apologies to J.R.R. Tolkien

Fulltimer50

Kerrville, Tx

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Posted: 01/19/12 02:56pm Link  |  Print  |  Notify Moderator

Turning radius has to do as much with the truck as the trailer. The sharper the turning radius on the truck the sharper it will be with the trailer.
The wheel location on a 5th wheel is no where close to that of a semi trailer.


George

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Brewurown

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Posted: 01/19/12 03:08pm Link  |  Print  |  Notify Moderator

I would think that turning radius would depend on the TV wheelbase. I have a long wheelbase and I need 40 acres.


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NC Hauler

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Posted: 01/19/12 03:13pm Link  |  Print  |  Notify Moderator

I too have a long wheel base truck, but I turn my 39' 6" 5er around in our cul-de-sac. When I make the turn, the inside tires "skew" until I complete my turn, but with the wheels half way back on the 5er compared to all the way back on the semi-trailer, it makes for a tighter turning radius. I could measure across the cul-de-sac, which I take every foot to use to make my turn around in if that would help, but I believe most would be surprised with how little it does take to turn around an almost 40' 5er hooked to a long bed Crew Cab dually.....I'm speaking from experience...I have to do it everytime I bring my 5er home from a trip so that I can back my 5er into my drive way.


On edit: I don't have to dodge anything when turning around in the cul-de-sac...it's not like pulling into a filling station and trying to avoid hitting fuel pumps or poles, etc (meaning having to make an even wider turn)...I'm talking about just making, basically, a U-turn with truck and 5er.


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Francesca Knowles

Port Hadlock, Washington

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Posted: 01/19/12 03:13pm Link  |  Print  |  Notify Moderator

As I understand it, turning radius is affected by both the length of the rig and the placement of its wheels.

I'm hoping somebody out there understands the math involved well enough to tell me how the formula would differ for a rig with the wheels (pivot points) situated differently than those on the rig in the picture.

When trip planning, the widths of ingress/egress roads and sharpness of campground curves is readily available...
It's be nice to be able to make a real determination of accessibility before deciding on destinations!

sirdrakejr

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Posted: 01/19/12 03:25pm Link  |  Print  |  Notify Moderator

While the turning radius of a 5th wheel turning is shorter, the rear end swing of a 5th wheel will be much more. A semi truck's rear end has a very short overhang and the swing is minimal. A 5th wheel has almost 1/2 of it's length as overhang and that swing will give you grief if you do NOT remember to allow for it and miss any objects close to the end of your combo.

Practice, practice, practice. [emoticon]

Frank


2011 Palomino Maverick 1000SLLB on a 2004 Dodge Quadcab CTD Ram3500 SRW long bed equipped with Timbren springs, Stable Load bump stops, Rickson 19.5" wheels/"G" range tires and a Helwig "Big Wig" rear anti sway bar.


skylos

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Posted: 01/19/12 03:35pm Link  |  Print  |  Notify Moderator

The radius is reduced by the shorter kingpin-to-rear-axles distance. Effectively, your 42' in the picture is like, 20'.

The back end of the trailer will swing out a good distance, but that can be over grass or sidewalks or whatever, its merely important that it not be trees...

John Bridge

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Posted: 01/19/12 03:41pm Link  |  Print  |  Notify Moderator

Turning a fifth wheel trailer has more to do with the distance between the pin and the midway point between the trailer axles. I have a long wheelbase truck, and I, too, can turn my forty-foot fiver in my cul de sac. I probably wouldn't be able to do it with a forty-foot semi-trailer without meeting up with myself. [emoticon]


Semi-"retarred" in 2006. :-) 2008 Newmar Cypress 5th wheel, 2008 Dodge diesel dually to pull it with.


RoyF

Fayetteville Arkansas

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Posted: 01/19/12 04:12pm Link  |  Print  |  Notify Moderator

If the truck can make a u-turn, the trailer (fifth-wheel or other) follows. The outside track will be made by the steering tire of the truck. The length or wheelbase of the trailer is a red herring here.

ps: I think I misunderstood the question. I was thinking about minimum size of a complete circle. Disregard this, please!

kab449

PA

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Posted: 01/19/12 04:23pm Link  |  Print  |  Notify Moderator

Each trailer will be different depending on the distance from the kingpin to the center point of the trailers axles. Your task will be to learn when driving your rig how far to the inside the trailer tires track in relation to the track of your tv. This is a judgment learned as previously stated by practice, practice, practice.


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