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Author Topic: King Pins  (Read 134 times)

Wasoki

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King Pins
« on: September 16, 2018, 02:52:24 PM »
I'll expose my lack of knowledge about the truck based mechanics under our motor home (it is a Ford chassis). 

I noticed that the front tires were showing a wear pattern that I had not expected or noticed before ( even wear on the both tires on the outer edges ) 

So, when I took it in for a oil change, I asked that the wear be looked at.

When I picked up the unit, the mechanic told me that he had detected some up and down movement in the king pins.  He reported that there was no side to side movement. He said that it wasn't anything that needed attention now, but by the time we got back from Florida, it might need attention  ($700 to $800 of attention).

My ignorance includes even knowing what the king pins are or do, how long they should last, and if they need attention, might this be a warranty issue?  (Warranty ends in November.)

Can anyone enlighten me?
By the way, upon inspecting the remaining tires, all six have the same water pattern. Inflation issue?
Jim Sullivan
Newmar Canyon Star 3710
WASOKI
(We Are Spending Our Kids Inheritance)

Gary RV_Wizard

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Re: King Pins
« Reply #1 on: September 16, 2018, 03:19:16 PM »
The king pins support the front wheels on a solid axle suspension in a manner that allows the wheels to pivot (steer). Worn king pins allow some sloppy movement and can cause tire wear in odd patterns.  The size & weight of the front wheel assembly on a modern motorhome make it doubtful that a human can determine wear by simply pushing on it, as can sometimes be done on smaller, lighter car wheels.

You didn't mention the year or mileage on that set of tires, so hard to assess how serious it is. Wear on the outer edge is more likely an alignment problem, but conceivably there is a wear problem in the front suspension & steering. I would not leap to that conclusion, though.

Wear on the outer edges of BOTH front tires suggests either excessive toe in on both, or a problem with wheel camber (wheels not perfectly vertical.  With a solid axle front suspension,camber angle may mean the axle is slightly bent or that the front end is overloaded.  Truck alignment shops know how to bend it back, though.

Wear on the outer edge of the rear duals (all 4?) is very unusual.  It would take a highly skilled chassis alignment shop to check that out, someboy like Josams in Orlando.

Tire pressure issues won't cause wear on just one edge. Underinflation wears both edges, and overinflation wears the middle.
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Wasoki

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Re: King Pins
« Reply #2 on: September 18, 2018, 11:25:09 AM »
Thanks for the informative response.  The Unit is a 2017 with about 14,000 miles on it.

The three times when I weighed the unit, it has been well below capacity on all wheels.

I spoke with a rep from the tire manufacturer.  He ask for pictures which I have not gotten yet.   Based on my description and answers to his questions, he kind of felt that it was a normal wear pattern.

All in all, I am not concerned enough at this point to delay out planned escape to warmer climes in about 5 weeks...
Jim Sullivan
Newmar Canyon Star 3710
WASOKI
(We Are Spending Our Kids Inheritance)

Gary RV_Wizard

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Re: King Pins
« Reply #3 on: September 18, 2018, 11:55:40 AM »
I had a Dodge Ram pick-up that exhibited wear like that when the weight on the front end changed. If it was aligned properly when unloaded (normal driving), it would wear on the outside when the 5W was attached. The weight on the back lifted the front enough that the camber changed. If I aligned with a load on, then it was off the other way when empty.  I ended up just rotating tires periodically to distribute the wear on all 4 (it wasn't a dually).
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL