A towing question...

cowman

cowman

Final Approach
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I know POA has plenty of other people who tow trailers and we like to argue about trivial things....

So, every component in a hitch system has a weigh rating on it right? The vehicle has one, the hitch receiver has one, the ball mount, the ball.... but what about this pin?

upload_2021-10-13_12-52-50.png

I have never seen a weight rating on these? Doesn't that seem odd? I just bought a heavy ball mount that was completely solid- not a square tube and it was rated at 17,000# but I'm still going to use one of these pins which are the same I use on a 5,000 or 7,500# ball mount. It holds the whole thing together but it sort of looks like the weakest link. Obviously it's hardened steel but you'd think they'd have a weight rating since everything else does and now this fact is bugging me.
 
Look up the shear strength of mild steel, double it (because there are two places in shear), and compare that to the load.

Then note that the pin doesn’t have to be any stronger than the cross section of the square tubing that the solid square stock goes into. ;)
 
It doesn't bear any weight. It get's tugged in shear until the trailer gets moving and pushed in shear during braking but those loads are pretty small. Like how all that thrust from your engine-prop is pulling the plane with 4 little bolts.
 
No weight rating because it doesn’t bear weight, but the pin exceeds the rating of the hitch.
 
I would guess that the shear rating for the same size pin without the lock would be the same.A34F9E6B-06AD-4CAB-979D-95ABC3FED241.jpeg
 
Stewartb said:
It doesn't bear any weight. It get's tugged in shear until the trailer gets moving and pushed in shear during braking but those loads are pretty small. Like how all that thrust from your engine-prop is pulling the plane with 4 little bolts.
Click to expand...

^This. No reason for a weight rating as it isn't weight-bearing. As long as the shear strength exceeds the push/pull of the trailer load it isn't much of a factor.
 
You will rip the hitch off the truck before you shear that pin.
 
I've had that thought too. Posters above covered it well, but I'll add that if it makes you feel any better, I used to tow a 40,000 lb grain wagon behind my pickup; I've got a massive cushioned hitch made for that task, and it's the same stupid little pin. I've also pulled a loaded semi that died on the road a couple miles from home. Any shock that would break that pin would break the truck's traction long before.
 
I'll bet if you look at the package it came in, it will say a range of class hitches it's for....class ii-iv, etc....
 
Yep, you're never going to break that pin, as long as it's steel. It's in double shear...I'd expect it to cut through the receiver tubing before it fails. The weak point for many add-on hitches are the bolts holding it onto the frame of the truck. If they get loose, the back and forth motion, coupled with corrosion, can gradually cut them in two. Those bolts are smaller, they're threaded, and they're usually in single shear.

The component that seems suspect to me are the 3 way hitch balls. Where instead of the normal 1" or 1-1/4" steel threaded stud, the balls are held on with a little filet weld all the way around. As Jim K points out, the traction of the tow vehicle or trailer would probably give way first, but I have seen some lousy looking welds on the 3 way mounts.
 
3F236F56-FE1F-4DA9-9C4C-B60F39BDD9E1.jpeg

Yup still got the pin… tried pushing a way to heavy trailer uphill and it twisted the whole mount like a pretzel- pin was unaffected.

I get your question though. One thing I would say from the original post though is I’d doubt they are hardened steel- we wouldn’t want the brittleness that comes w hardened…
 
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I always thought the tongue was the fragile component .... they are stamped out of sheet metal and use tiny pins securing the latching mechanism .... yet seldom hear of them failing and if they do it is because somebody used an undersized ball .

The horror stories are how the receiver hitch is installed on the car or truck .... sometimes just a couple bolts holding the hitch onto a flimsy bumper bracket and no cross bracing to frame ... I worked 30 years in autobody and have seen some frightening installations.

Huckster79's picture is an example ..... rugged receiver made of 1/4 inch thick metal .... but then welded onto truck cross-member that is made from 1/8 inch thick metal ..... yet this is a common way to do it and failure is rare except in overload.

The most important thing for safe trailer towing is to get just the right amount of weight on the tongue to hold it in place with the main load carried by the trailer axles .... that way the hitch-tongue is lightly loaded except for acceleration and braking ..... just like a properly balanced boat trailer ..... on level ground you can pick up the hitch with one hand and move it around easily.

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I got to thinking about this when I was getting a new ball mount for use with this trailer- the one I had been using got repurposed. It’s in theory a 10,000# trailer and most of the ball mounts I found were rated 7500… only other option was this beefy solid one that’s rated at 17,000…. probably overkill the 7500 would have worked for any normal load but still I like overbuilt. Anyway that’s what got me thinking about the pin- it was the only part of the whole apparatus that I had no rating for.

3c967bf0-ed27-44d0-b7a7-2d9c429c3aca-jpeg.95157
 
A Martin said:
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The most important thing for safe trailer towing is to get just the right amount of weight on the tongue to hold it in place with the main load carried by the trailer axles .... that way the hitch-tongue is lightly loaded except for acceleration and braking ..... just like a properly balanced boat trailer ..... on level ground you can pick up the hitch with one hand and move it around easily.

.
Click to expand...

It is usually best to target tongue load of 10-15% of total trailer (+ cargo) mass from a stability standpoint for a tag trailer. If that is too much for the vehicle's Rear Gross Axle Weight Rating, then switch over to a load distributing hitch and shift some of that tongue load to the front axle. Said as someone who has spent a couple of decades making a living doing vehicle dynamics and stability control tuning including limit handling with loaded trailers - you are better off having too much tongue load than too little.
 
Matthew Johnson said:
It is usually best to target tongue load of 10-15% of total trailer (+ cargo) mass from a stability standpoint for a tag trailer. If that is too much for the vehicle's Rear Gross Axle Weight Rating, then switch over to a load distributing hitch and shift some of that tongue load to the front axle. Said as someone who has spent a couple of decades making a living doing vehicle dynamics and stability control tuning including limit handling with loaded trailers - you are better off having too much tongue load than too little.
Click to expand...

The wrinkle is there isn’t really a great apparatus to determine actual tongue weight, everyone just kind of eyeballs it and if the truck isn’t squatting down way low or being lifted way up it’s assumed close enough.
 
cowman said:
The wrinkle is there isn’t really a great apparatus to determine actual tongue weight, everyone just kind of eyeballs it and if the truck isn’t squatting down way low or being lifted way up it’s assumed close enough.
Click to expand...

At work, it is easy with drive on scales and a jack that spans the trailer scales for the tongue...

In the real world, I tend to measure hitch deflection unloaded vs. with someone of known mass standing on the bumper then compare how much the hitch deflects when the trailer is lowered onto it and compare (i.e. assuming linear spring rate on the rear axle of the vehicle). I also have enough experience to feel when the trailer starts to get unstable and either commit to driving well under that speed for the remainder of the trip or stop and move the load forward (if insufficient tongue load).

I.e. if a 200 lb person moves the ball down ~1 inch, I guesstimate the trailer is ~4k, and when I drop the trailer onto the ball the ball moves down between 2 and 3 inches I would call it good enough to start the trip and feel out the stability as I drive.

Same thing applies with a load distributing hitch, and you can guesstimate how much load you take off of the rear axle by how much the rear of the vehicle lifts back up when tightening the chains.

Edit: it is actually a lot quicker and easier to do the real world method above, just less precise than doing it the 'work' way...
 
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I have always thought that this is a great demonstration of trailer stability vs. tongue load (it also gets less stable as vehicle speed increases):
 
Here’s the sketchiest thing I ever towed and the only one that scared me. For those who don’t know it’s a sickle bar mower. In my cases used to cut grass for hay. The bar is vertical for transport but lays flat and cuts grass kind of like a hedge trimmer.

E1E35AA0-2C0D-40F8-B733-886A341CEB94.jpeg D385AA14-EA43-460C-8C0D-DCBABF9AA4F7.jpeg



Didn’t have a trailer handy, bought it from someone a fair distance from home. I’ve towed farm implements before, you just drive slow and careful. Well, with this thing above around 35MPH it would randomly start violently oscillating and shaking the whole truck. Really if it hadn’t been significantly lighter than what it was being towed by it would have yanked me off the road. That was a looong drive home.
 
Matthew Johnson said:
It is usually best to target tongue load of 10-15% of total trailer (+ cargo) mass from a stability standpoint for a tag trailer. If that is too much for the vehicle's Rear Gross Axle Weight Rating, then switch over to a load distributing hitch and shift some of that tongue load to the front axle. Said as someone who has spent a couple of decades making a living doing vehicle dynamics and stability control tuning including limit handling with loaded trailers - you are better off having too much tongue load than too little.
Click to expand...
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Yes .... without a load on the tongue a trailer will fishtail down the road .... my sister and husband bought a Mercedes SUV and a Boler type trailer and decided to travel 15 hours to my cottage and go "camping" .... neither of them had any mechanical knowledge and decided to load the trailer heavy on the back to reduce the hitch load .... so much that the tongue was actually lifting the rear of the SUV .... once on the highway it fishtailed so bad they almost lost control .... slowed down to 40 mph and limped to the next town where a trailer company installed an exotic anti-sway system between the hitch and trailer .... helped a bit but when they arrived at my place they were stressed and haggard .

Before they left I removed the sway bar apparatus and showed them how to properly load the trailer .... they were skeptical but I told them I guaranteed the results .... a week later I got a nice letter from her full of cash .... she said the trailer towed perfect and she made the dealer giver her money back and sent it to me as a gift.

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cowman said:
The wrinkle is there isn’t really a great apparatus to determine actual tongue weight, everyone just kind of eyeballs it and if the truck isn’t squatting down way low or being lifted way up it’s assumed close enough.
Click to expand...

Yes , I often used the eyeball method .... carried a wooden yardstick for dipping fuel tanks ... I would lean it against the rear bumper and watch it as I drove equipment on the trailer .... I was hauling a 6000 lb trencher and liked to see one inch down deflection on the i ton truck bumper .... once I determined the sweet spot I then loaded the trailer same each time.

trivia:
I once got caught on a dirt trail during a heavy rain .... could not get any traction .... off loaded the heavy trencher to drive truck and trailer to a good road then walk back and drive the trencher there .... but traction was even worse ..... then loaded the equipment as far forward on the trailer as possible .... front of the truck came up by 6 inches or so ..... with all the weight on the truck rear axle it drove out of there without much tire spin .... live and learn.

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more trailer trivia:

At one time I ran an anhydrous ammonia plant filling hundreds of farm tanks .... they use a solid front axle with a vertical hinge pin ... sometimes these tanks would start to fishtail down the road causing deadly accidents if the ammonia was released ..... but some tanks towed perfectly straight and safe ..... it all comes down to keeping the pin and plates well oiled and greased and they tow great .... just like the semi drivers who scrupulously grease their fifth wheel to prevent sway and fishtail.

amonia hitch.JPG
 
Matthew Johnson said:
It is usually best to target tongue load of 10-15% of total trailer (+ cargo) mass from a stability standpoint for a tag trailer. If that is too much for the vehicle's Rear Gross Axle Weight Rating, then switch over to a load distributing hitch and shift some of that tongue load to the front axle. Said as someone who has spent a couple of decades making a living doing vehicle dynamics and stability control tuning including limit handling with loaded trailers - you are better off having too much tongue load than too little.
Click to expand...

Was going to say the same thing. There isn't any way you're lifting the tongue of my boat trailer with one hand unless you're an avid Strong Man Competition contestant, lol. My boat and trailer weigh around 4,500lbs total, and the axles are placed to make sure there is adequate tongue weight. I've never weighed the tongue with a scale, but I bet it's at least 400lbs. Tandem axle/triple axle trailers are usually good with 7-10% tongue weight. Single axles should have 10% at a minimum.
 
cowman said:
The wrinkle is there isn’t really a great apparatus to determine actual tongue weight, everyone just kind of eyeballs it and if the truck isn’t squatting down way low or being lifted way up it’s assumed close enough.
Click to expand...
I use one of these:
https://www.sherline.com/product/sherline-trailer-tongue-weight-scale/
I place it on a floor jack and lift the tongue.
As a side note, I sometimes place it on a floor jack and jack up each axle at the spring plate to get a per wheel weight if I am worried.
Tony T.
 
China-origin hitch pin

Labelled shear strength: 40,000psi
Actual strength: 500psi
 
Let'sgoflying! said:
China-origin hitch pin

Labelled shear strength: 40,000psi
Actual strength: 500psi
Click to expand...

This past summer, one of the guys that was helping bring gear to our scout camp managed to bend the pivot pin on a bike rack hitch. Bent about 20 degrees.

4 mountain bikes, figure 35 lbs each, bike rack maybe 70 lbs.

Was getting slammed around hard on a rough dirt and rock mountain road for 45 minutes.

I'm certain that pin was made of chinesium.
 
cowman said:
The wrinkle is there isn’t really a great apparatus to determine actual tongue weight, everyone just kind of eyeballs it and if the truck isn’t squatting down way low or being lifted way up it’s assumed close enough.
Click to expand...
Bathroom scale under the jack? I was actually going to try it this weekend because towing my motorcycles last weekend I noticed that my truck squatted an awful lot.
 
Yes you can measure tongue weight (even a heavy tongue) with a bathroom scale (and a beam and fulcrum)

 
A Martin said:
. it all comes down to keeping the pin and plates well oiled and greased and they tow great .... just like the semi drivers who scrupulously grease their fifth wheel to prevent sway and fishtail.

View attachment 100946
Click to expand...

I never thought about it, but any stiction on any of the pivots means the rig won't self center, so it makes perfect sense. Back when I towed a lot, I always put a little dollop of grease on my finger and coated the ball, it made for a quieter ride.
 
Matthew said:
And remember to cross the safety chains:

Click to expand...
I run them through the loops on the hitch and connect them with a lock - can't bounce out and come unhooked and it's harder to steal my rusty beat up Horrible Freight trailer.
 
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