Tires are cupping... what am I missing?

So it appears that my Cooper AT3 LT's are cupping quite badly. I've got about 30k miles on them and have them rotated and balanced every 5k miles at my local @DiscountTire. They are factory size LT275/65R18. At my last rotations approximately 4k miles ago with 7-8/32's remaining, I noticed they were getting louder and found a few outer lugs wearing a little unevenly. The service advisor noticed a little bit of uneven wear and suggested I lower the tire pressure. I had them at 45 psi and dropped them to 42 psi; as a side note, the other sets of LT tires I've run have been much less sensitive to tire pressure and wear, but I still try to aim for an optimal contact patch.

I had to travel quite a bit this week at freeway speeds and they were annoyingly thump-thump-thump loud, so upon inspection this evening I found about every third or fourth outer lug significantly cupped on both front tires, as well as the section row of tread cupping as well. The rear tire also have some minor cupping on the outer lugs that I noticed at the last rotation.

My suspension is new; maybe 9k miles on 6112's up front set at the lowest setting, and half that on my Dobinson MRA rears (the matching fronts are sitting in the box waiting for me to install them when the truck and I have some downtime...). Before the 6112's, I briefly had Eibach 2.0's set pretty low. Before that, a fairly worn set of 6112/5160's. One of the 5160's was making noise so I figured it was time for a new setup. Anyways, I wouldn't think that a worn suspension is the culprit...

I had the truck aligned regularly using two different shops depending on who was available: I had it aligned every time that I made any suspension changes, and when the tires were new. Camber and caster are good, toe was out a tiny scoche that I could feel as a minor pull when braking hard, so they made a minor adjustment. Camber and caster have never actually been adjusted for the life of the vehicle. I might look for the last alignment numbers and go over it again. But, alignment has been maintained.

Front end components are original, but I don't see any signs of bad ball joints, control arm bushings, or tie rods. Doesn't mean something isn't worn out, I just don't see it. Had a few places give it a looksee and nothing seemed awry. It tracks down the road fine and takes corners predictably and correctly.

So what am I missing? Any pro tips for checking and diagnosing an existing issue? I've spent plenty of time wrenching and have several mechanic friends that usually get me sorted out, but I also know when to ask for help or ideas. Could a sticky caliper be causing the issue? I'll check the pad wear on all eight pads.

Or is it really just the tires? Discount Tire did have a very difficult time balancing them when new and I had to have them rebalanced three times in the first 1000 miles. One of the tech's told me that they could only get one tire down to '60' and another down to '45' with a roadforce balance. I'm not 100% clear on what that means exactly, but he noted that they try to aim for '25' or less. My previous set of tires were AT3 XLT's in 275/70R18 and they made it past 50k without much issue so I've been surprised out how much trouble this set has given me. Thinking I might just ditch them and try Firestone's Destination XT since Nokian hasn't released the new Outpost nAT in any viable sizes. Anyways, looking for some ideas. Sorry for the novel..

Edit: forgot to add that I swapped the factory TRD wheels for a set of takeoff 2.5gen TRD wheels last year. The new wheels had 2k miles on them from a '19; I had them powder coated locally before installing them. I wouldn't think that I have a bent wheel, but is there a simple way to check? Could the tire store dismount the tires and and spin up each rim for me to check for balance? I know I'd be out $100 for mount and dismount.

 

Sounds to me like you got a bad set of tires. Uneven rubber wear, inability to balance properly from the start, then rebalancing required? I had similar issue with a set of tires about 15 years ago. After 6 months of fighting them, my tire dealer got me a full warranty replacement. No problems after that.

 

Are the tires rotated front to rear each time? When I rotate mine one time is side to side, next front to rear. That seems to keep any feathering at bay.

 

Factory size LT275/65R18, but running them at 45 PSI? Am I reading that right?

... What's the sticker on the inside of your driver door say you should be running your tires at, at that size LT tire?

 

I know you don't think it's the suspension, but FWIW bad or inadequate shocks can cause tires to wear funny and prematurely. Good luck!

 

The sticker on the truck is for the tires that came on the truck, or equivalent replacements.
If you switch to a tire with a different rating, then you go by what's on the tire.
You wouldn't run a 10 ply E rated tire at 32 psi.
Running 45 psi, I'm guessing @blenton has 6 ply C tires.

 

Tire pressure should be adjusted depending on what is best for the usage at the time. It's not a one size fits all.

 

I called discount the other day to verify my install date and mileage, and make sure I didn’t miss any rotations. They said they cross rotate them to mitigate cupping issues. So, fronts go straight back, rears, go across and up. Every tire I have run feathers a little on the outside edge but it's barely noticeable.

What @RichterScale said.. They are load range E tires not the factory p rated tires so going by the inflation table for the LT tire and finding the load equivalent pressure, the LT tires need 42-45psi to carry the same load as the p rated tires at 33 psi (what's on the door placard). Even still, if you look at the notes from Michelin on the LTX AT2 that came factory with many TRD tundras, they note that max load is reached on their p275/65r18 tire at 35 psi but max tire psi is 51 psi for 'ride and handling tuning'. So I ran my takeoff LTX At2's at 42-45 psi as well. My truck is close to payload most of the time.

My last set of AT3 XLT's made it past 50k with the same usage. I retired them at 4-5/32's but they didn't start giving me any wear or noise issues until after 40k, so I was very surprised to be fighting these ones so much.

Thanks. I'll be making time to swap out the front shocks soon. I might pull apart the 6112's for inspection just because.

 

After some more digging, it appears that Cooper had some issues manufacturing tires in 275/65r18 across several brands and lines including Cooper, Mastercraft, and Mickey Thompson among others. They issued a voluntary recall for certain MFG dates. My last set were 275/70R18 because they didn't make the XLT in 275/65r18 so maybe they are still having issues with this tire size.

 

If your truck is on the heavy side, 45psi might be a little too low for an E tire. My guess is they are running a little deformed at that pressure and that's where the wear is happening. I know it will make the ride rougher, but try bumping them up to 60-65 psi.
I ran the coopers on my 2011 and tried running them a little too soft and they didn't last a year. Same thing, outside edges wore off.
Put Es on the 2015 and tried running them at 45psi (knowing I shouldn't) because the ride was just too rough. 8' bed was loaded with tools and had a fiberglass cap, plus towed a lot, so I was heavy too. But they were wearing too fast. So bumped them to 65 psi and just dealt with the rough ride.
I'll be getting C tires next. That way I can run them at 45 and just pump em up when I tow or haul.

 

Thanks for the suggestion. Yes, my truck is a bit heavier than most; I'm virtually always hauling and often towing. I will play with the pressures some more but I was getting a tad more wear down the center of the tread before, which would denote being slightly over inflated. As well, the front tires are cupping worse that the rears. My old tire shop pumped my tires up to 65 psi once and I immediately noticed the truck darting all over the road until I dropped them down below 55 psi.

 

I just swapped out the front suspension in the event that the Bilsteins were bad. I didn’t see anything obvious with the front end components; the upper ball joints and outer tie rod boots were a bit crusty but I didn’t feel any play in them. Since I swapped coilover assemblies, I disconnected the lower ball joints from the bottom of the spindle and while they felt loose, they didn’t feel sloppy or have any noticeable play. I may assemble the spring compressor that I bought (but never used cuz I had a local Toyota Off-road shop put them together for me) and pull the springs off the bilsteins to inspect them but they didn’t have any obvious signs of failure or leakage.

I had the tires rotated and balanced a week or so ago. Unfortunately, the front tires continue to wear strangely on both the outside and inside edges as if they are cupping. Since the tires were previously on the back, it was pretty obvious that they are wearing funny, though I’m surprised it happened so quickly after rotating and balancing.

 

That was where I was going next. I can’t seem to find the most recent alignment sheet so I guess it’s off the alignment shop.

 

Having the same problems OP I just installed new 6112s front lowest setting and 5100s in the rear, everything else is solid. I think it’s just these trucks. I’m running factory size 18” Falken Wildpeak AT3W. Last set of tires did the same thing, they were Hankooks AT.

 

So, after two shops telling me all is well, turns out my outer tie rod ends are worn out. I wondered if that were the case and suspected the last place that aligned it as they said they had to really crank on the jam nut to break it free. They turned the heat on it and burned the boot off but neglected to tell me.

So I’m waiting at the shop to get the tire rod ends and boot replaced. Hopefully it fixes things but I can definitely see how would cause the tire wear I’m seeing.

 

Thanks. I ran through the three items on their list several times in the last year, which is why I posted for more insight. As noted above, tires were rotated and balanced regularly (every 5k); aligned at a minimum every 20k, or with suspension changes (three times in the last year); and suspension inspected and changed thrice (but not due to work or bad suspension parts, at least as I could tell).

Two of the shops that did alignments on it told me the front end components were all in good shape (I asked them to inspect and replace before going in for the alignment). Today, the truck is being aligned at a shop recommended to me by a local yota 4x4 shop; they found some bad tie rods. Go figure. We'll see if it really fixes it, but it make sense. I'll put new tires on before the snow starts flying - maybe sooner - and I didn't want to muck up a brand new set of tires.