Calculating how an extension de-rates your receiver.

[mkirsch]

How would you go about calculating how much a receiver should be de-rated with a 14" extension?

Secondarily, does anybody know what a Curt 24" receiver tube is rated for?

http://www.curtmfg.com/part/49240

That's what I used to make my extension. It is cross-drilled to provide 14" of extension, and extends through the receiver box on my truck's Reese Titan.

[Reddog1]

Kayteg1 wrote:

Reddog1 wrote:
Show us the math.

Wayne

https://en.wikipedia.org/wiki/Conjugate_beam_method :B

Your response suggest you do not know how calculate the weight on the rear axle with an extension. I am disappointed, I thought knew what you were posting about.

Wayne

[mkirsch]

I'm a mechanical engineer, a tinkerer, a fabricator, and a farm boy, so I know exactly where you're headed...

Maybe in an EXTREME case, you could end up with over 5000lbs...

Just off the top of my head, I'm estimating it would take a tongue weight of around 2000lbs on the extension with no weight distribution to achieve that.

The truck would be undriveable with so little weight on the front wheels. I'd surely notice right away when I couldn't turn.

The joke's on you though: Even with 5000lbs on the rear axle, I'd still be under the truck's RAWR of 9350, and well under the tire limits of >10,000lbs.

[Kayteg1]

Reddog1 wrote:
Show us the math.

Wayne

https://en.wikipedia.org/wiki/Conjugate_beam_method :B

[billtex]

Reddog1 wrote:

Kayteg1 wrote:

mkirsch wrote:


My TC weighs <2000lbs sopping wet, so I still have about 3500lbs of payload capacity left before GVWR, and over 4000lbs before I hit the GAWR.

You are still ignoring actual rear axle weight.
Even with 2000lb camper, when you put 700lb tongue on the extension you MIGHT end with over 5000 lb on rear axle.

Show us the math.

Wayne

Show us your rig too kayteg...

[Reddog1]

Kayteg1 wrote:

mkirsch wrote:


My TC weighs <2000lbs sopping wet, so I still have about 3500lbs of payload capacity left before GVWR, and over 4000lbs before I hit the GAWR.

You are still ignoring actual rear axle weight.
Even with 2000lb camper, when you put 700lb tongue on the extension you MIGHT end with over 5000 lb on rear axle.

Show us the math.

Wayne

[Kayteg1]

mkirsch wrote:


My TC weighs <2000lbs sopping wet, so I still have about 3500lbs of payload capacity left before GVWR, and over 4000lbs before I hit the GAWR.

You are still ignoring actual rear axle weight.
Even with 2000lb camper, when you put 700lb tongue on the extension you MIGHT end with over 5000 lb on rear axle.

[mkirsch]

Kayteg1 wrote:
Are you planning to tow with your TC on?
The extension might hold the tongue weight, but make sure your tires and rear axle can.
Depend on the truck the 800lb tongue weight on extension can add up to 1500 lb to the rear axle

I normally tow with the TC on. Either a ~4000lb enclosed utility trailer (with extension), or a ~10000lb flatbed (withOUT extension).

My TC weighs <2000lbs sopping wet, so I still have about 3500lbs of payload capacity left before GVWR, and over 4000lbs before I hit the GAWR.

Last weekend was almost a roadside emergency situation, where the plan was to swap trailers with the guy who was having overheating issues. He would tow my 4000lb trailer while I towed his much larger 7000lb travel trailer.

In the end, we transferred 1000lbs of his equipment to my trailer, and took the longer flatter route home. He had to stop once to add coolant, and it would go over 240 degrees on the hills, but he nursed it home.

[bjbear]

ticki2 wrote:
From TCU http://www.visualsc.com/hitch_calc.htm

The rule of thumb I use is:
Revised Receiver Rating = (11 / (11 + EL)) * Mfg Rating
Where EL = the length of your extension in inches & Mfg Rating = the published rating for your receiver.

So assuming you would put a regular ball & mount in your 14" extension, you would derate your receiver to 44% of whatever the rating is from the manufacturer.

Or you can use this chart.

Assume your 14" extension will give a total extension of 25" when the ball/mount is added.

[Kayteg1]

Are you planning to tow with your TC on?
The extension might hold the tongue weight, but make sure your tires and rear axle can.
Depend on the truck the 800lb tongue weight on extension can add up to 1500 lb to the rear axle

[mkirsch]

I *was* looking at towing a ~7000lb travel trailer last weekend. My friend was having an overheating problem with his 2001 Suburban.

Hmm, so Curt rates their 24" extension at 800/8000lbs with WD. My 14" receiver tube extension should be made from at least as good a material as that one, so it should be good for at least 800/8000lbs with WD, and probably more.

[ticki2]

From TCU http://www.visualsc.com/hitch_calc.htm

[Super_Dave]

This looks like it gives Curt extension ratings.

24" Curt

[Super_Dave]

What kind of a load are you putting on it?