There’s been debate amongst professionals whether welding a kingpin and resizing it to spec would be a safe practice.

Here is an interesting thought that’s been tossed around by owner-operators and trailer mechanics. Can you refurbish a kingpin without removing it from the bolster plate on a trailer?  Theoretically, weld up a worn pin and grind it smooth to original specs. Well, that’s the thought.

900 words  4.5-minute read   

Can you do it without destroying the integrity and strength of the pin?

As a truck and trailer mechanic “but not a metallurgist.” This is my thinking because, in the end, the proof is in the pudding. This information is from experience, watching, learning and doing.

We all know a kingpin can get worn out from natural means, or premature wear from sloppy jaws on a 5th wheel of the truck. But having said that, let’s not let the drivers off the hook.  Some have bad habits of hitting the pin too hard when connecting the power unit to the trailer. That could show signs of a different issue.

However, the worn-out pin has to be repaired.

Have you ever considered just welding it and resurfacing it down to specifications? That could be more economical if it was done safely. Well, that’s where this whole story comes into play. Should you or could you weld it without doing damage to the pin?

There seem to be a few reputable companies doing that very thing and to my knowledge, some have been in business for at least thirty years.

But let’s assume the trailer is reasonably new and shows no sign of frame damage or worn-out pick-up plate or frame damage, but the pin is worn out of specs. You know and I know this is a hugely time-consuming job regardless of the trailer.

Can a Trailer Kingpin be repaired safely without overhauling the front half of the trailer?

Photo of 3 three different types of KingPins

Let me explain how it started for me.

Looking after a reasonably small but busy fleet of highway trucks and trailers a camper came wheeling up to the door. A French-speaking dude from Quebec jumped out of his truck and greets me like we were old-time buddies.

But after the nice’s were over, he explained that he welds up worn-out trailer kingpins. And if I didn’t mind, he would check the fleet over for damaged pins and for free no less. Sure, but I explain to him up-front.  I’m not comfortable with welding such an important part of any highway trailer. 

He assures me welding up Kingpins on a Highway Trailer is safe.

He assured me it was a safe and cost-saving practice and his company had insurance for whatever, I guess for whatever goes wrong?

As far as the kingpins, I regularly check them over for wear and damage. (Youtube Video) But having said that, I did have a few pins that were borderline out of specs.  And were on my scheduled agenda for repair.

After this fella did his walkabout he found a few that needed attention and into the office he when to plead his case to the owner.

Two hours of my labour per pin compared to a possible 20 hours or better to replace the part by surgically removing the floor, blah, blah, blah.

That was a no-brainer price wise and thankfully it wasn’t my call. But I was interested in the procedure and the end results.

The afternoon has come and gone with two trailers king-pins repaired and looking like new.

As a mechanic, I was skeptical about the procedure and whether the strength or the integrity of the pin was compromised. But there were no signs of any difference after the four years of ownership before the trailers were traded in.


Inspect the plate closely for any structural damage due to rot or worn out or broken or bent components. But if everything is secured, and the trailer is not that old, then reconditioning these pins could be an option.

We all have to feel safe on the road and it’s up to the mechanic’s judgment whether going down that avenue is comfortable when certifying the unit.

Mechanics Story

Having inspected a pick-up plate that showed an uneasy sign of other things going on and, with a worn-out pin, I made a judgment call and opened up the floor. And, I’m glad I did! Cross members were damaged and rotten.

In the end, it’s you’re Call!

The advertisement states;

Before a Kingpin can be refurbished it must pass a general inspection. The Upper Coupler/Grid assembly inspection is performed to ensure that there is no apparent structural damage. The pin is checked for squareness and proper height. The bolster plate thickness is measured ultrasonically and visually inspected for cracks and deformations. If the upper coupler does not meet the inspection criteria, then refurbishment is not recommended.

Check out my article on why truck wheels fly off.

When evaluating fleets our technicians will inspect multiple trailers on a single visit. The wear levels and structural assessment is noted on an inspection report that is provided to the fleet service manager.

That is the Kingpin Specialists Ad.

Welding up a trailer Kingpin

Last Comment.

So, there You Have It. I’ve replaced many kingpins in my career and this is only my opinion as a trailer mechanic turned blogger.

I’m not endorsing this company or any others that practice this procedure. I’m just stating my experience with a welded kingpin procedure. (Youtube Video) Can you refurbish a highway trailer kingpin? Well, you decide?

Thanks for reading my take on welding kingpin and please bookmark my site, I have more transportation articles.   

If you found my story informative please remember to show appreciation by Buying me a Coffee.