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I am posting this to share my experience with Goodyear Duratracs, stock size 265/60/18, in hopes this might be helpful to others.

I installed these tires at 29K miles and at about 65k, road noise started to get louder which I dismissed as part of the aging process of the tires.
At 69K miles, I started to see more prominent cupping on the inside edge of the front tires.
I have run the tires between 33 and 36 psi for most of the time since new. The Duratracs are rated as a 50K tire and was concerned about premature wear. All my research pointed to failing shocks.

I had the alignment done twice with Firestones lifetime alignment warranty with the hopes of a quick fix, but the cupping, noise, and abysmal mpg were still present.
Firestone reported that because of the aggressive nature of the tires, the oem shocks were not able to suitable for it.

I even took it to the dealer and invoked the Maxcare warranty and they reported that that the non-oem tire and the Duratracs were the cause of weird noises that I reported. Jeep dealer said they replaced my custom wheels and duratracs with oem set and tires and reported noises went away in this diagnosis process. Skeptical, I replaced and verified with my own set of oems and touring tires (which are very low in tread and smooth) and also confirmed Jeep's conclusion.

This process led me to think about increasing my Duratrac pressures up to allow the tire to ride the middle tread more and lessen the shoulder of the tread where cupping was occurring.
The Duratracs have a maximum cold pressure rating of 51 psi, so I increased my cold pressures to 46 psi (90% of max).
Since doing this, I have found my mpg's have increased to where I expected them to be, my tire noise is diminished, cupping appears to have also diminished!
I am happy about having discovered this adjustment because now I am fairly confident I will be able to get the last 10K miles remaining on the 50K mile rated tires, and I no longer feel pressured to upgrade the shocks (although, I was looking forward getting a lift-and-level).
This is not perfect I know, more center-tread emphasis, road imperfections are transmitted more, possible lessened handling characteristic, and steering feels lighter (like the oem set), but I get full use of the tires and despite the mentioned cons, I do not get the feeling of any real safety compromise. So, for now it is all good!
 

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Just be careful...running them up at 46 psi cold could potentially wear them in the middle of the tread. That said, I suspect that these specific tires are not suited to the lower 33 psi on the placard just due to their nature. You may find that something in the 38-40 psi (cold) range might bridge the gap between wear and ride.
 

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Seems like it would be a brutally stiff ride. Honestly, if the tires have a warranty I would simply contact Goodyear as opposed to going overboard on OE tire pressure recommendations especially if it's the same tire size as OE. As Jim said you'll just cause additional unwanted wear and tear.
 

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I have my doubts that the OEM shocks can't handle G/Y Duratrac tires.....
I can believe your OEM shocks are worn....

You mentioned you were running aftermarket wheels, what was the Offset?

I could see a big difference in wheel offset, plus running tires at too low a pressure and some wear in the suspension/shocks could be result in the cupping.... ...and if it didn't do it when you first installed it, but does it now, the change in offset would create stress on the suspension and thus increase wear and that resulted in happening later and not right away.... ...or as you speculated, the tires might have changed with age and wear....

The Duratracs have a maximum cold pressure rating of 51 psi, so I increased my cold pressures to 46 psi (90% of max).
Since doing this, I have found my mpg's have increased to where I expected them to be, my tire noise is diminished, cupping appears to have also diminished!
I am happy about having discovered this adjustment because now I am fairly confident I will be able to get the last 10K miles remaining on the 50K mile rated tires, and I no longer feel pressured to upgrade the shocks (although, I was looking forward getting a lift-and-level).
This is not perfect I know, more center-tread emphasis, road imperfections are transmitted more, possible lessened handling characteristic, and steering feels lighter (like the oem set), but I get full use of the tires and despite the mentioned cons, I do not get the feeling of any real safety compromise. So, for now it is all good!
The 51PSI Max Pressure tires I have owned, I found required the higher pressure than the 44PSI Max Pressure tires that were previously on the vehicle.... ....and it was proportional to the Max Pressure....
i.e. if I found 85% of the max pressure of 44PSI worked best, than 85% of 51PSI worked the same in a 51PSI Max press tire....
that might not be true of all 51PSI max press tires....
So monitor your tread wear and adjust tire pressure accordingly, which you should be doing regardless of what pressure you run in the tires....

My 2011 WK2 near 100k miles, picked up a rocking in the steering wheel at highway speeds and some vibration.... ...then I noticed some cupping on the tires....
I got new shocks, while installing them I noticed one of my upper control arms had the bushings sheared through.. ...I got new control arms and it fixed all the issues.....
...the bushings in the UCA are near impossible to see, you really can't tell if its bad unless you seperate the steering knuckle from the UCA....
 

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Was the alignment performed at the time the tires were installed? Either way, do you happen to have a printout you can post up so I can see the measurements? Most places, especially the rather large majority of chain stores DO NOT perform a complete alignment when customers purchase a "lifetime" package. They set the front toe angle and call it done.
 

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Discussion Starter #6
Just be careful...running them up at 46 psi cold could potentially wear them in the middle of the tread. That said, I suspect that these specific tires are not suited to the lower 33 psi on the placard just due to their nature. You may find that something in the 38-40 psi (cold) range might bridge the gap between wear and ride.
Jim,
I agree, I fully expect that the center will wear faster.
Assuming I have 10K left, my hope is that by the time it comes to the end of tread life, since the cupping is bad, that the center will level out with the cupped portions.
 

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Discussion Starter #7 (Edited)
Seems like it would be a brutally stiff ride. Honestly, if the tires have a warranty I would simply contact Goodyear as opposed to going overboard on OE tire pressure recommendations especially if it's the same tire size as OE. As Jim said you'll just cause additional unwanted wear and tear.
MDK210, it really is not as extreme as it might seem. the GC has some squishy equipment to begin with so it is forgiving.
At 80% of tread life used, I wont put time into pursuing this with the manufacturer of the tire. If the I can get the remaining 10K out of the tire with the pressure change adjustment, I would be really happy and would consider the same set as the replacement as its been a very good tire with good on-road/off-road mannerism for first 35-40K.

Reading up on this issue on different forums and sources, it appears that running aggressive tires on 4x4, wranglers, and such, cupping appears to be the status quote and exacerbates this condition especially when rotations are neglected.
 

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Discussion Starter #8
I have my doubts that the OEM shocks can't handle G/Y Duratrac tires.....
I can believe your OEM shocks are worn....

You mentioned you were running aftermarket wheels, what was the Offset?

I could see a big difference in wheel offset, plus running tires at too low a pressure and some wear in the suspension/shocks could be result in the cupping.... ...and if it didn't do it when you first installed it, but does it now, the change in offset would create stress on the suspension and thus increase wear and that resulted in happening later and not right away.... ...or as you speculated, the tires might have changed with age and wear....


The 51PSI Max Pressure tires I have owned, I found required the higher pressure than the 44PSI Max Pressure tires that were previously on the vehicle.... ....and it was proportional to the Max Pressure....
i.e. if I found 85% of the max pressure of 44PSI worked best, than 85% of 51PSI worked the same in a 51PSI Max press tire....
that might not be true of all 51PSI max press tires....
So monitor your tread wear and adjust tire pressure accordingly, which you should be doing regardless of what pressure you run in the tires....

My 2011 WK2 near 100k miles, picked up a rocking in the steering wheel at highway speeds and some vibration.... ...then I noticed some cupping on the tires....
I got new shocks, while installing them I noticed one of my upper control arms had the bushings sheared through.. ...I got new control arms and it fixed all the issues.....
...the bushings in the UCA are near impossible to see, you really can't tell if its bad unless you separate the steering knuckle from the UCA....
Mongo54, you bring up some points that I also factored into my analysis of this but did not mention to simplify my story. However, since you bring it up, OEM offset is +56, custom is +30 (they stick out more than OEM). The change does increase the cantilever in the geometry. This together with knobbier, aggressive tires was considered but not ruled out.

So the lingering rhetorical questions are, why was it fine for the first 35-40K and now the problem emerges...is it a matter of gradual decline of the shocks and the problem is just more evident over time...has the tire material changed over time due to e.g. UV, etc...is it just the nature of the beast as other hard core 4x4 users have reported and accepted when running aggressive tread patterns or possibly just the procedure that one has to take in the latter tread life of this tire. Finally, I had not considered other component failures (UCA) which are not yet obvious.

As was mentioned in an earlier post, and as you have found, playing with tire pressures might just be the solution for certain tires.
 

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Discussion Starter #9
Was the alignment performed at the time the tires were installed? Either way, do you happen to have a printout you can post up so I can see the measurements? Most places, especially the rather large majority of chain stores DO NOT perform a complete alignment when customers purchase a "lifetime" package. They set the front toe angle and call it done.
Ratchet, no alignment was done at the original installation of the wheel set. If I recall correctly, the first alignment was done around 64K then again around 67K. Each time the alignment results was off to varying degrees. Alignment parameter include camber, caster, toe at each of the four corners. Include also total toe, steer ahead, and thrust angle were also reported.

The interesting thing is after the first alignment, I could feel the improvement behind the wheel and at the tank. It accelerated more effortlessly and with the feeling of less drag. MPG calculations confirmed this feeling. After a couple thousand miles I began to suspect that issues were returning with each successive fill up and MPG calculation. I went back for the second alignment and found it off again which is why I considered a more deep rooted problem in the shocks or suspension components as would be the characteristic of cupping.

It remains now that with the increased tire pressures, riding with the emphasis on the center tread and lessening the weight on the shoulders, the GC gives the sense of easier accelerations, steers with better agility, and MPGs remain higher. With every passing confirmation-al mile, I am coming to the conclusion that one can not apply door jam pressure specs universally to all tires and that one has to adjust things based on the situation.
 

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Just keep in mind that with a contact patch that emphasizes the center of the tread because of the high PSI, you'll potentially have handling performance compromises in wet weather, etc.
 

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Mongo54, you bring up some points that I also factored into my analysis of this but did not mention to simplify my story. However, since you bring it up, OEM offset is +56, custom is +30 (they stick out more than OEM). The change does increase the cantilever in the geometry. This together with knobbier, aggressive tires was considered but not ruled out.

So the lingering rhetorical questions are, why was it fine for the first 35-40K and now the problem emerges...is it a matter of gradual decline of the shocks and the problem is just more evident over time...has the tire material changed over time due to e.g. UV, etc...is it just the nature of the beast as other hard core 4x4 users have reported and accepted when running aggressive tread patterns or possibly just the procedure that one has to take in the latter tread life of this tire. Finally, I had not considered other component failures (UCA) which are not yet obvious.

As was mentioned in an earlier post, and as you have found, playing with tire pressures might just be the solution for certain tires.
Offset affects Scrub Radius.... ....Cantilever? You'll have to explain that, I no idea what Cantilever refers to in suspension geometry? Its not a bridge....

You want a zero scrub radius, the bigger the difference between the geometric balance point of the suspension and the center of the tire patch, the greater the torque arm between force and point of rotation....

So with a 26.4mm positive increase in offset, you've got more than an inch of torque arm and the drag of the tires or the force from putting power to the tires are trying to turn the tires toe in/out..... ...the suspension retains the wheels in their position, but under greater strain......

So what happens to moving parts when they are put under greater pressure and stress? They wear out faster.....

AFA Cupping....
The tires wears more where there is more pressure.....
So too much or too little air pressure in the tire makes more pressure on the inside of the tread or the outside of the tread and it wears more where there is more pressure....
Too much Camber +/- tilts the tire and one side of the tread wears faster than the other...
To much toe in/out, bends the treads blocks over on the outside/inside edge of the tire as it rolls it scrubs over the surface, so the outside/inside tread blocks wear at an angle, this is called feathering and some people that don't know tires too well will call it cupping. What I've seen of many dealerships, they could call feathering cupping....

All examples of uneven tire wear....

Then there's cupping, all the above examples the wear is uneven left to right on the tire looking at it head on, its cross section, because the position of tire tread is not square with the road or its direction of travel.... but the wear is even around the circumference of the tire, because the entire tire rolls evenly on the surface....

Cupping is not even around the circumference of the tire, and the only way for the wear not to be even around the circumference of the tire is because the tire is not rolling evenly on the surface.... ....the tire has to be bouncing or wobbling as it rolls.... The only way tires bounce is shocks are bad, their balance is way off, something is broken or worn out in the suspension, the only way tires wobble is if there is something broken or worn out in the suspension.... ....finally, it is possible a tire that has bad rubber or construction could have soft spots in the tire that will wear faster than the rest of the tire, this would cause cupping, if this was true, it would be a design flaw in the tire and the tires of this brand and model would have reputation of this cupping....

Tire pressure causing cupping, I suppose its possible, but it would be a minor factor that would have to in combination with other factors like wear or damage in the suspension....

VW has a TPMS system on some of their vehicles that has no tire pressure sensor, it simply uses wheel speed and compares them to figure out if a tire has deflated slightly.... ...it also using wheel speed so fine it looking for torsional vibration, cause if a tire is too low on air, it will create torsional vibrations, (note how a flat tire feels rough and makes a god awful racket).... ...so perhaps the effects of tires too low on air might contribute to some cupping...
 

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Discussion Starter #12
Mongo53, clarification needed... I never said "...Tire pressure causing cupping...".
I do believe that increased tire pressure is mitigating the effects of whatever is causing the cupping because it is shifting the pressure point of the tire from the shoulder to the center of the tire.
My theory is that a combination of increased drag of aggressive tires, relatively soft oem shocks, and an increase in cantilevering of the suspension contribute to the cupping effect.
A picture is worth a thousand words, cantilever:
220736

The moment (rotational torque) around point A will be increased due to the change in offset to +30.
 

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Honestly, it would be very surprising to me if cupping "isn't" caused by air pressure not appropriate for the tire. If the wear was on one edge, it would point to alignment, but if the wear is on both edges, something is amiss with the tire pressure or the wheel isn't appropriate for the tire's width, etc.
 

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I'm sorry, I misunderstood the issue, then. That normally sounds like alignment...but you stated you had that checked multiple times. Strange.
 

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Mongo53, clarification needed... I never said "...Tire pressure causing cupping...".
I do believe that increased tire pressure is mitigating the effects of whatever is causing the cupping because it is shifting the pressure point of the tire from the shoulder to the center of the tire.
My theory is that a combination of increased drag of aggressive tires, relatively soft oem shocks, and an increase in cantilevering of the suspension contribute to the cupping effect.
A picture is worth a thousand words, cantilever:
View attachment 220736
The moment (rotational torque) around point A will be increased due to the change in offset to +30.
I never claimed you did say tire pressure causes cupping.... ...I detailed what causes cupping... ...I speculated how tire pressure and offset "might" contribute to it.... ....I contrasted the difference between uneven tire wear and cupping, using tire pressure and alignment as examples... ...i.e. there is uneven tire wear from incorrect tire pressure and alignment, then there is cupping which is a whole other animal of uneven tire wear.... ...if that came across as a strawman argument, my apologies, that is not what I said nor intended...

Offset changing Scrub Radius is well document as the main effect....

Your drawing and definition of moment (Torque by definition is rotational) has me lost... ...what part of the suspension is Point A and what part is Point P and what is the deflection depicted in the suspension or the steering?

Look at the graphic above, changing offset introduces a torque arm applied to the steering axis where none had existed before... If that is what you're talking about, we agree...

Does offset extend or reduce a lever arm of the suspension, I can see that, but to what extent. You changed that lever an 1" when you started with 24" lever (as an example, I don't know the actual specs).... ....now I can see folks that do silly things with a foot of offset change, that really causing a problem....

Scrub Radius on the other hand, you introduced a torque around the steering axis where none had been before, so that's divide by zero error.... ...another way to say it, the forces on the steering axis were balanced, and by changing the offset you put them out of balance...

Even that would not cause cupping, but I can see it contributing to wear, and wear that allows wheels/tires to bounce or wobble as they roll down the road cause cupping.
Honestly, it would be very surprising to me if cupping "isn't" caused by air pressure not appropriate for the tire. If the wear was on one edge, it would point to alignment, but if the wear is on both edges, something is amiss with the tire pressure or the wheel isn't appropriate for the tire's width, etc.

Tire wear faster in one spot more than another if there is more pressure on one spot more than another...
Tires roll...
So how do you get more pressure at every 20° of rotation than the other 19° of rotation? Or alternating and staggered on each outside edge....

The tire has to be bouncing or wobbling to get cupping.... ...bouncing or wobbling is how you get more wear every X number of degrees around the tires, or wobbling giving you more wear in a staggered pattern on each outside edge ever X degrees of rotation....

So a very under-inflated tire, I could see introducing bouncing or wobbling, but I imagine so under-inflated we're talking bulged and heated sidewalls, a tire bulged so bad it is not rotating smoothly.... ...a tire a few PSI low, I can't see how it would cause Cupping, it would have to be wear/damage to the suspension, or tires way out of balance.....
 

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Discussion Starter #17
I'm sorry, I misunderstood the issue, then. That normally sounds like alignment...but you stated you had that checked multiple times. Strange.
No problem Jim.
Sometimes, the subtle things get lost in too many details.

The small change that I applied appears to be remedying the situation so i'll stay on course and find out if ultimately I can reach 50K miles with a leveled out tread (or lack thereof ?)
 

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Mongo, I was confusing "cupping" with the wood version which would be evenly across the (tire) rather than the scalloping you show in your photos. It happens... ;)
 

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Wood Cupping? Is that where a board curls and is no longer flat?
Feathering is often confused with Cupping. My guess, most folks look at both cupping and feather and think, how does that happen? So they mix them up.

Too much toe in/out causes the feathering, its uneven on the tread block, but it's the same pattern all the way around the circumference of the tire.
 

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I suspect most cupping is caused by an interplay of tire design, tire balance, parts tolerances, wheel alignment, and low inflation pressure which result in a harmonic being set up in the tread. The outer tread area has less restraint against movement then inner area so the cupping occurs on the outer edges where the tread has more ability to move up down and sideways under load and the harmonics makes the load non-uniform resulting in the non-uniform wear. Low inflation pressure and out of balance would be the first things I would check as solutions if the cupping is caught before it so bad it's not correctable.

220768
 
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