Adjusting kingpin height

[David Greenwell]

I am getting some inside wear on the rear passenger side tire on my Cougar. One recommendation is to adjust the pin height to pull the rig as level as possible. I believe I’m a little high on the nose (pic below) and am looking for input on lowering the kingpin to level the rig. Would you recommend doing this and is it easy to do by myself?

 

[Eman85]

Can't help you on kingpin. Did you measure and check to see if the axle is square or if there is wear and play in the mountings?

 

[NH_Bulldog]

What is your hitch set at now? My hitch has three positions and I would adjust the hitch before I messed with the pin box. Neither is a good option if you have 6" or less space between the top of the bed rail of the truck and the underside of the 5th wheel overhang. While 7"-8" is ideal, you can lower the hitch (a little) if absolutely necessary, but don't go to less than 6" of clearance.

That all being said, one tire wearing odd is not necessarily an indication of being too nose-high, since it would affect both rear tires similarly. It could be a variety of factors including interior weight distribution, damaged or worn components in the running gear, bearings, a pot hole, a curb impact, etc. Have you inspected the springs, spring hangers, spring shackle bolts, wheel bearings, etc.? If all are original (and/or you do not have wet-bolts), I would look at worn components first. How old are the tires (not how many miles, but how old), and do the size, rating and inflation pressure match the loading sticker on the front corner of the camper?

 

[chuckster57]

I agree with the above.

 

[David Greenwell]

Can't help you on kingpin. Did you measure and check to see if the axle is square or if there is wear and play in the mountings?

Thanks.. have not measured for square, but bearings are good and solid. Read that a long straight edge between the front and rear wheels will indicate an alignment issue. Will be doing that this week.

 

[DutchmenSport]

On a previous camper, I had one tire that wore uneven. When it became uncomfortable for me to continue using it, I had a new tire installed to replace it. The other 3 were perfectly fine, so I left them. The new tire ran for several more years and never showed any type of uneven wear. All I could figure out was, the tire itself was a defective tire from the beginning and it simply couldn't handle the punishment like the other 3 could.

Then, on my current fifth wheel, about 3 years ago, my RV dealership repair shop figured out I had a bent axle. I had one tire wearing uneven and asked them about it. I was having bearings repacked. When they examined everything, they found the axle bent. Long story short, I purchased a new identical tire, they replaced with a new axle, and it's been 3 years and thousands and thousands of miles on those tires and none of them are showing any signs of uneven wear anywhere.

So, your problem could any number of issues. Everything from an inferior tire, to scrubbing when backing up, to shackles, adjustments, broken welds, or even the brake on that specific wheel grabbing more aggressively than the other 3 wheels.

I do not think the height of the king pin is your problem though. If the height of the king pin was too high, the tire on the opposite side would be worn also. So, (personally), I think something else is going on.

My advise, have a "professional" examine your axle, wheels, and everything involved and see what they come up with. It could be a simple alignment. But if that is the case.... what caused the miss-alignment? And is something bent that is causing the miss-alignment now. That's why I suggest having a second set of eyes examine it, unless you know what you are doing and feel comfortable making corrections yourself. If not, then get it inspected.

Good luck!

 

[Eman85]

On a standard trailer I just measure from the ball to the axle near each wheel, left to right should be the same. Bolt for the brake backing plate is a good spot. On a fifth wheel you could drop a plumb bob and measure from that. Then check the rear axle to see if it's parallel.

 

[chuckster57]

There is a form that we fill out to measure axle squareness. As I remember all measurements hade to be within 1/16”.

https://lci-support-doc.s3.amazonaws.com/technical-information-sheets/axles-and-suspension/spring%20axles/ccd-0001920.pdf

 

[wiredgeorge]

Can't imagine nose high would cause one tire to wear unevenly. Suggest you get under the camper and check your axle to see if it is not bent the same as the other axle. They should have a bow in them with the highest part toward the camper. I have only had a tire(s) wearing unevenly if an axle was bent. I replaced the axle as I could find NO shop locally that would bend the axle that was bent incorrectly. Suggest you make a signature with year, make and model of your camper as well as the same for you tow vehicle. Makes life easier when trying to answer questions with some context.

 

[David Greenwell]

Can't imagine nose high would cause one tire to wear unevenly. Suggest you get under the camper and check your axle to see if it is not bent the same as the other axle. They should have a bow in them with the highest part toward the camper. I have only had a tire(s) wearing unevenly if an axle was bent. I replaced the axle as I could find NO shop locally that would bend the axle that was bent incorrectly. Suggest you make a signature with year, make and model of your camper as well as the same for you tow vehicle. Makes life easier when trying to answer questions with some context.

Thanks for the info and updated my signature… great suggestion!