R/Front tire cupping

I have 295/70/18 (34.5 x 12 x 18) Cooper Discoverer STT PRO tires on my 2010 Ford F-350 4x4 diesel. I put them on back in October, and I've probably rotated them 3x's since then (at least).

The problem is that I've been having problems with the r/front tire cupping. I've had it aligned twice, but the problem hasn't been resolved. The only time I've experienced cupping in a tire was from a worn out shock.

At my last oil change the garage said I was going to need to replace my r/front tie rod. Not sure if that would cause the tires to cup.

This is the fastest I've went through a set of tires. These are almost down to the wear bars, and it hasn't even been a full year yet.

Any suggestions as to what would cause the cupping on the r/front tire only?

Oh ya, it has a Rough Country 3-inch lift on it.

Same as far as the shocks go, have you checked to make sure that shock is in working order?

On my fiancé's 99 350 i replaced the steering and track bar. That fixed hers. I've been told that the bj front axles will wear on the inside due to the bj's being worn and still be tight.

Balance can cause cupping, but usually you know about it from the vibration first.

You can't get good alignment with a loose tie rod end. Regardless, being out of line wouldn't cause cupping, just uneven wear. Any death wobble? Rowdy F, if a BJ is tight, it isn't worn

×2 on the ball joint, tight = not worn.

Is the cupping relatively even across the tread? or is it significantly more on one edge than the other?

The latter could indeed (at least partially) be due to alignment (though I'm thinking camber or wheel bearing problem most likely if it's only one side). A loose TRE would cause toe misalignment, which normally would affect both front tires.

However I think another possibility might be the tires themselves...
In the past, Cooper STT tires always seemed extremely susceptible to cupping (I've seen it numerous times including on a buddy's '80 Blazer and a '91 Toyota, one or both fronts would always start to cup no matter what he did, often within just a few thousand miles). I'm not familiar with the newer STT Pro version, but maybe it's still a possibility.

Haywire6000 said:

Same as far as the shocks go, have you checked to make sure that shock is in working order?

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Yes, even though the shocks were new (came with the lift), I replaced them a month ago with Bilsteins.

Rowdy Fitzgerald said:

On my fiancé's 99 350 i replaced the steering and track bar. That fixed hers. I've been told that the bj front axles will wear on the inside due to the bj's being worn and still be tight.

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The track bar has new bushings

Andy D said:

You can't get good alignment with a loose tie rod end. Regardless, being out of line wouldn't cause cupping, just uneven wear. Any death wobble? Rowdy F, if a BJ is tight, it isn't worn

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I've only experienced death wobble once. It was a year ago with the old tires, and before I put the lift on.

4x4junkie said:

×2 on the ball joint, tight = not worn.

Is the cupping relatively even across the tread? or is it significantly more on one edge than the other?

The latter could indeed (at least partially) be due to alignment (though I'm thinking camber or wheel bearing problem most likely if it's only one side). A loose TRE would cause toe misalignment, which normally would affect both front tires.

However I think another possibility might be the tires themselves...
In the past, Cooper STT tires always seemed extremely susceptible to cupping (I've seen it numerous times including on a buddy's '80 Blazer and a '91 Toyota, one or both fronts would always start to cup no matter what he did, often within just a few thousand miles). I'm not familiar with the newer STT Pro version, but maybe it's still a possibility.

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The tires haven't gotten pretty worn, and they were just rotated about 7,000 miles ago (just got back from a 7,000 mile road trip), but the cupping looks to be just to the outside of the centerline of the tire.

So basically [==I/=] [ edge = tread = tread I centerline / cupping = tread ] edge

I bought a new steering stabilizer when I got the Bilstein shocks, but didn't replace it before my trip, because I couldn't get it unbolted from the draglink. I'm going to take another crack at it this weekend. I hit the damn thing with a sledge hammer, and it wouldn't budge.

I've considered the possibility that it could simply be the tire brand, especially after a guy recently told me he had problems with another tire brand cupping. It just seems weird to me that the r/front would cup, and not the l/front.

Oh ya, the truck drifts to the right. That's why I had it aligned a second time. The shop told me that whoever installed the lift, may not have got the locating pins in their holes when they put the rear lift blocks on, which could be pushing it to the right. I'm the one who installed the lift. I know the blocks, pins, and alignment holes have to align when you install a rear block

I need to replace these tires soon, but I want to figure out the cupping issue first. I need to find a different brand 295/70/18. I'm suppose to be able to fit 35x12.50x18's but the inside edge of the drivers side tire rubbed making a tight left turn when the 295's were new, and they're basically a 34.50x12x18 tire. I figure the 35's would rub for sure.

Here's the tires when they were new, and how close they are to the radius arm when it's in park with the wheel turned left:


I'd take a photo of the cupping, but it's kind of hard to spot right now.

my guess is that cupping occurred after the lift?

What I meant was they're tight when you try to check them for play by band but the weight of the truck causes the top to tip in. But since the cupping is just inside of center line, I'm going to assume it's a mixture of a bad shock and worn BJ's which is effecting the camber.

Jim Oaks said:

The tires haven't gotten pretty worn, and they were just rotated about 7,000 miles ago (just got back from a 7,000 mile road trip), but the cupping looks to be just to the outside of the centerline of the tire.

So basically [==I/=] [ edge = tread = tread I centerline / cupping = tread ] edge

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My gut feeling seems pretty much on those tires. Alignment issues I'm thinking would present themselves more at the edge or shoulder of the tread, rather than in the middle, even if slightly off-center.
I've seen severe cupping on Pro-Comp MTs too, which I understand are also made by Cooper Tire. My best semi-logical guess is it's from an undamped resonance from the tread blocks that resonates within the tire carcass causing the funny wear (at least that's about all I can come up with if everything else checks OK).

I've had good luck with BFG's tires, the only time I ever saw any hint of cupping was one time I didn't rotate them for over 12K miles (maybe coincidence, but I recall it was the RF tire that it became visible first on mine as well). I don't think I've ever seen cupping issues with Toyo M/Ts.