When to replace the hitch pin?

[swimmer_spe]

The pin for holding the hitch into the receiver is the only real thing holding our trailers to our trucks. Mine is new, but it got me thinking, how often should it be replaced?

[BarneyS]

I'm sure the OP has the idea by now and since the bickering has started I am going to close this one. Thanks for all your participation.
Barney

[valhalla360]

Grit dog wrote:

OMG you should give up arguing about this…. You’re not making any tangible sense, especially in the context of this (ridiculous) original question.
So wrought iron, or pig iron ? which is basically just high carbon ore, not actually made into any final product.). And none of which are made into hitch pins.

So you don't understand anything about metallurgy and are just going to throw out terms with "iron" in them hoping something sticks.

In engineering, we often use a worst case scenario (with a factor of safety) when the full information isn't readily available...but I'm sure you know better even if you don't bother reading the full post.

[Cummins12V98]

Does my CUMMINS-HEMI have a hitch pin?????

[Grit_dog]

valhalla360 wrote:

Grit dog wrote:
^Yup, you’re correct. Although also correct. I didn’t pickup on your reference to iron, as in cast iron, of which NO hitch pins are made of. And I understand this concept better than most.
Why would you even say that? Be like using a wooden dowel or titanium as odd ball “examples”.

I never said "cast iron" which is an entirely different material and completely unsuitable as it's highly brittle. I used "iron" as I'm not sure of the exact formulation of steel used and the strength can vary wildly based on the specific formulation (though typically far stronger than iron), so iron provides a lower floor on strength...and it's still several times stronger than is required.

OMG you should give up arguing about this…. You’re not making any tangible sense, especially in the context of this (ridiculous) original question.
So wrought iron, or pig iron ? which is basically just high carbon ore, not actually made into any final product.). And none of which are made into hitch pins.

[valhalla360]

swimmer_spe wrote:

valhalla360 wrote:

mosseater wrote:
Any idea what the shear forces required to chop it in two? There are anomalies in this world but betting the farm very few ever are sheared. The receiver welds would probably fail before that pin would shear. I'd sooner keep the one I have road tested than risk a new one these days.

5/8inch pin has a cross sectional area of around 0.30in^2.

It will depend on the specific steel but say we made one of iron (not steel for a worst case scenario). Iron has a shear strength of around 26,000PSI.

So each end of the pin would have a strength of around 7,800 but since both ends would have to shear to get a failure, 15,600lb.

A descent quality steel (nothing exotic) can be twice that shear strength.

Keep in mind, when you tow, you aren't lifting the weight of the trailer. The force needed to pull the trailer is a small fraction of the trailer weight. Even in a panic stop, the trailer would push the truck into a skid long before the force reached the weight of the trailer.

So long as there is no sign of damage or deformation, it should be fine.

Thank you for the math.

Now, what about fatigue? If you bought it brand new and it is used regularly and is 10,20+ years old?

Never heard of one that has failed. I suppose if you do something utterly stupid, it's possible but just no a big concern.

The above would be a worst case where the pin is providing all the pulling and stopping power.
- As noted by others, the friction in the receiver tube provides much of the pulling power. Particularly with a WDH, it's not just the dead weight on the hitch creating friction.
- The trailer brakes should provide most of the stopping power.
- The maximum pulling power before the drive axle wheels spin is a tiny fraction of the strength.
- In practice, it's probably less than 10% of the trailer weight just rolling down a level highway. Going up a 6% grade, it should be 6% plus wind resistance...maybe 1500-2000lb of force.

Fatigue in that scenario isn't really a concern. If you have a 20yr old pin that's been in use daily with the truck maxed out on tow rating, go ahead and replace it if it makes you feel better but it's not an issue.

[valhalla360]

Grit dog wrote:
^Yup, you’re correct. Although also correct. I didn’t pickup on your reference to iron, as in cast iron, of which NO hitch pins are made of. And I understand this concept better than most.
Why would you even say that? Be like using a wooden dowel or titanium as odd ball “examples”.

I never said "cast iron" which is an entirely different material and completely unsuitable as it's highly brittle. I used "iron" as I'm not sure of the exact formulation of steel used and the strength can vary wildly based on the specific formulation (though typically far stronger than iron), so iron provides a lower floor on strength...and it's still several times stronger than is required.

[Grit_dog]

JRscooby wrote:

SUMRX4 wrote:
The pin really isn't holding any weight. I towed an 8,000Lb tractor on a flatbed trailer about 60 miles once and after the trip I realized I never put the pin into the hitch. Won't do that again but that taught me the pin isn't doing any work.

Thank you.
I have had to cut pins to get them out when somebody did something silly like put cable in receiver, then pin thru eye, but then all the force is center of pin. But I have had to cut more of the locking pins, where snot gets in key-hole, key won't work

An extreme example of the same thing that happens with reducer sleeves sometimes.

[Grit_dog]

swimmer_spe wrote:

valhalla360 wrote:

mosseater wrote:
Any idea what the shear forces required to chop it in two? There are anomalies in this world but betting the farm very few ever are sheared. The receiver welds would probably fail before that pin would shear. I'd sooner keep the one I have road tested than risk a new one these days.

5/8inch pin has a cross sectional area of around 0.30in^2.

It will depend on the specific steel but say we made one of iron (not steel for a worst case scenario). Iron has a shear strength of around 26,000PSI.

So each end of the pin would have a strength of around 7,800 but since both ends would have to shear to get a failure, 15,600lb.

A descent quality steel (nothing exotic) can be twice that shear strength.

Keep in mind, when you tow, you aren't lifting the weight of the trailer. The force needed to pull the trailer is a small fraction of the trailer weight. Even in a panic stop, the trailer would push the truck into a skid long before the force reached the weight of the trailer.

So long as there is no sign of damage or deformation, it should be fine.

Thank you for the math.

Now, what about fatigue? If you bought it brand new and it is used regularly and is 10,20+ years old?

A. His “math” ain’t right for STEEL, which all hitch pins are made of. And a “decent quality” steel is far more than double the shear value of cast iron.
B. “Fatigue” isn’t a real world consideration unless you could somehow get enough stress into it to have repeated elastic deformation (you can’t and won’t) resulting in strain hardening which will eventually leading to cracking.
However plastic deformation would cause it to be rendered unsafe. Never gonna happen with a proper hitch setup but somewhat common when those silly hitch stinger reducers are used on larger receivers to fit smaller stingers.
Finally physical wear could cause it to have reduces strength. For steel rigging subject to cross sectional loss due to wear, the criteria is a reduction of 10% or more of the effective cross section.

At the end of the day, unless you bend a pin as I described above, there is a 99.9999% chance that pin will outlast you, and your kids too. Maybe grandkids as well.

[JRscooby]

Grit dog wrote:

SUMRX4 wrote:
The pin really isn't holding any weight. I towed an 8,000Lb tractor on a flatbed trailer about 60 miles once and after the trip I realized I never put the pin into the hitch. Won't do that again but that taught me the pin isn't doing any work.

Your confusing ignorance and luck with physics….

There have been times when I have had to telescope dry tubes. The only way to do it with reasonable amount of force is make sure there is no side pressure. If you lift the ball mount too high it is harder to get it out. The same would apply with TW on the ball

[Grit_dog]

SUMRX4 wrote:
The pin really isn't holding any weight. I towed an 8,000Lb tractor on a flatbed trailer about 60 miles once and after the trip I realized I never put the pin into the hitch. Won't do that again but that taught me the pin isn't doing any work.

Your confusing ignorance and luck with physics….

[JRscooby]

SUMRX4 wrote:
The pin really isn't holding any weight. I towed an 8,000Lb tractor on a flatbed trailer about 60 miles once and after the trip I realized I never put the pin into the hitch. Won't do that again but that taught me the pin isn't doing any work.

Thank you.
I have had to cut pins to get them out when somebody did something silly like put cable in receiver, then pin thru eye, but then all the force is center of pin. But I have had to cut more of the locking pins, where snot gets in key-hole, key won't work

[SUMRX4]

The pin really isn't holding any weight. I towed an 8,000Lb tractor on a flatbed trailer about 60 miles once and after the trip I realized I never put the pin into the hitch. Won't do that again but that taught me the pin isn't doing any work.

[swimmer_spe]

valhalla360 wrote:

mosseater wrote:
Any idea what the shear forces required to chop it in two? There are anomalies in this world but betting the farm very few ever are sheared. The receiver welds would probably fail before that pin would shear. I'd sooner keep the one I have road tested than risk a new one these days.

5/8inch pin has a cross sectional area of around 0.30in^2.

It will depend on the specific steel but say we made one of iron (not steel for a worst case scenario). Iron has a shear strength of around 26,000PSI.

So each end of the pin would have a strength of around 7,800 but since both ends would have to shear to get a failure, 15,600lb.

A descent quality steel (nothing exotic) can be twice that shear strength.

Keep in mind, when you tow, you aren't lifting the weight of the trailer. The force needed to pull the trailer is a small fraction of the trailer weight. Even in a panic stop, the trailer would push the truck into a skid long before the force reached the weight of the trailer.

So long as there is no sign of damage or deformation, it should be fine.

Thank you for the math.

Now, what about fatigue? If you bought it brand new and it is used regularly and is 10,20+ years old?

[opnspaces]

Grit dog wrote:

opnspaces wrote:
If the pin is smooth and undamaged I would leave it alone. I would replace it if it's showing signs of damage like maybe the receiver tube gouging into the surface of the pin.

A few weeks ago I noticed that a replacement pin for a 2 inch receiver is a whole $3 on Amazon. At that price I ordered a few extras since I have multiple hitches at home. I also keep an extra in the center console of the Suburban as a just in case.
Amazon

$3 Scamazon hitch pins are maybe not the best purchase…I’ll leave it at that.

I stand by my first post. It's a Curt pin not a no name overseas knockoff. Here's another link to the Curtmfg.com website where the pin lists for $4.95 if it makes anybody feel better about purchasing.
Curtmfg