When to replace the hitch pin?
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?
Forum Discussion
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.
