Tire cupping

[Crusty old shellback]

So I'm getting severe tire cupping on the front tires.
2021 75th Power Wagon.
61K miles.
Factory bead lock rims.
MT Baja Boss 35x12.50R17. A out 30K Mike's on them now.

At first sign, I rotated tires and had alingmet rechecked. Set it to Thuren specs, which I've been running since the truck had 200 miles on it.
Still getting cupping. I added some balance beads just in case the tires were out of balance. Long story in a different thread as to why I wasn't running balance beads to start with with the tires. Not by my choice.
Still getting cupping.
Today I had the wife do the swing check while I crawled underneath to look. Only place I coukd see that had a bit of movement/play was the track bar bushing at the frame.
I get very slight vibration in the steering wheel, not nothing you really notice. Do get road noise.

So is it all caused by the track bar? Could it also be shocks?
This is my first coil sprung straight axle with a track bar.

Where do I spend my money to repair the issue?
TIA.
Crusty.

 

[LateToTheParty]

First place I would look is the shocks. Luckily you should be able to pull them and check them before you throw money at a new set.

Track bar could be to blame as well, but beyond what you already noticed, not much to examine, so it's just throwing $ at a guess at that point.

It could always be bearings or ball joints too, but I wouldn't think both sides would give up simultaneously for either.

 

[Crusty old shellback]

I had the bearings and ball joints checked when they did the alingment. I checked them as well when I rotated the tires and saw no play or grinding.
I checked the shocks and found no oil leaves on them.
Been wanting new shocks anyways.

 

[dieselscout80]

How often are you rotating your tires?

I rotate mine every 5k miles and have good wear patterns.

 

[G Mcpherson]

I would think at 61k on your shocks they are likely done. New shocks and go from there. Track bar bushing could be worn also.

 

[Crusty old shellback]

I rotate my tires every 5K. But have had to do it about every 2K now because of the cupping.

 

[H3LZSN1P3R]

It could be the tires themselves, did you have the same issue with the previous tires? some are more prone to cupping on a solid axle than others usually ones with a larger outer tread block, cupping on a solid axle is not uncommon thats where rotations come in to play.

 

[NC Rebel]

I have those same tires , no cupping on mine . I would guess maybe the shocks are worn out ?

 

[Crusty old shellback]

I put BFG KO2s 35x12.50R17 on at 200 miles and aligned to thuren specs. I put the Baja Boss on at 35K miles. I've always rotated around 5K miles.
I ran balance beads I. The tires up till the Baja Boss. The manager at 4WP would not install them. So I had to use weights. I recently put the beads back in, after I started getting the cupping issue.

I've contacted CJC about shocks and front track bar. Carli parts

 

[dslbrnr]

Do you have a printout on your alignment you could post?

 

[Crusty old shellback]

No. But basically it's set at 0 toe or slightly negative, no positive.
Castor I had set at 3.5 originally, but moved it back to 4.

 

[dslbrnr]

No. But basically it's set at 0 toe or slightly negative, no positive.
Castor I had set at 3.5 originally, but moved it back to 4.

My toe is slightly positive about 3-4° and caster slightly over 4°. I have slight cupping inside and outside edges after 5,000 miles.
I wonder if something wasn't tightened or shifted after your alignment. Is your cupping outside or the inside edges?

 

[Crusty old shellback]

My toe is slightly positive about 3-4° and caster slightly over 4°. I have slight cupping inside and outside edges after 5,000 miles.
I wonder if something wasn't tightened or shifted after your alignment. Is your cupping outside or the inside edges?

Both.
Factory specs allow a positive toe. Mine was past the negative factory spec when I got it. Thuren spec is 0 or slightly negative, no positive.

 

[AH64ID]

Both.
Factory specs allow a positive toe. Mine was past the negative factory spec when I got it. Thuren spec is 0 or slightly negative, no positive.

You’ve got that backwards. Slightly positive, no negative.

Your post from ‘21 shows you had .33° of positive toe from the factory.

https://cdn.shopify.com/s/files/1/0510/0529/2724/files/13-22_2500_3500_PW.pdf?v=1638206406

 

[Crusty old shellback]

Ok. Sorry I'm old and had a few beers since then.
I just remember it was out of spec from the factory and we set it as close to 0 as we coukd get without being positive.

 

[AH64ID]

Ok. Sorry I'm old and had a few beers since then.
I just remember it was out of spec from the factory and we set it as close to 0 as we coukd get without being positive.

You want it on the positive side of zero, even -0.1° is not good.

Your old post shows it was in total toe spec from the factory at 0.33° for OE specs. You had it set to 0.3°, within Thuren spec, at 3485 miles. Both those are positive readings.

Individually the tow at the tires was out of spec from the factory, but within spec for OE standards when combined.

Here is the old post for some memory jogging.

Factory alignment and Thuren specs

So, I have a stock '21 Power Wagon with 35" BFGS on stock factory beadlock rims. I put the tires on at 250 miles on the truck. Truck now has 3485 miles. I started seeing unusual wear on the outer edge of the front tires. I also had a vibration in the steering wheel between 65 and 70 MPH. So I...

hdrams.com

 

[Crusty old shellback]

Like I said, I'm old and had a few beers since then.
And I've had several alingments since then and a few different tires.

 

[Crusty old shellback]

So talking with CJC, looking at the Carli track bar and a set of their fox 2.0 ifp performance series shocks all around.

 

[H3LZSN1P3R]

So talking with CJC, looking at the Carli track bar and a set of their fox 2.0 ifp performance series shocks all around.

Typical of a shop like that, throw parts at it that wont fix the issue.

 

[AH64ID]

Like I said, I'm old and had a few beers since then.
And I've had several alingments since then and a few different tires.

Got the printouts on your most recent alignments?