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Old 02-15-2017, 06:01 PM
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Tire Cupping

Had a slight wobble in the steering so I took my Jeep down to Les Schwab today. I had them balance the spare and put it on the right front. He looked at the spare and asked which side and position it was on before. I said left front. The spare AND the current left front tire have cupping so it appears there is something wrong in my left front. I am running Old Man Emu nitro shocks front and back. Les Schwab claims it is a bad shock. I called Quadratec today and they claim is must be a ball joint and it would not be a shock. 2014 Rubicon X with almost 50,000 miles.

Ideas?

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Old 02-15-2017, 06:32 PM   #2
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Jack up the front end, grab tire at 12 & 6 is there any wobble?

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Old 02-15-2017, 07:52 PM
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Done. No wiggle at all. Could it be a bad shock?

I have sent an email to Old Man EMU/ARB as well.
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Old 02-15-2017, 10:56 PM   #4
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It could be, it's an easy check. Remove the shock and see if it rebounds. What psi are you running? Have you done a chalk test?
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Old 02-16-2017, 12:25 AM
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I have 285/70/17 Duratrac tires and I am running them at 34 PSI cold. Only the tires that get put into the front left position end up with cupping and it has only been happening in the past four months. The chalk test I did in spring 2014 showed that 34 PSI had a good even pattern. The tires have been on the Jeep since April 2014. I have almost 30,000 miles on them.

So, rebounding would be going back out in length, right? Silly question but just wanted to make sure my understanding of rebounding matches your comment.
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Old 02-16-2017, 12:27 AM   #6
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Here is an article discussing tire wear patterns and the causes:

Reading Tire Wear Patterns - Tire Review Magazine

It says: "Cupped or scalloped dips appearing around the surface of the tread could indicate loose, worn or bent suspension parts. Worn shock absorbers or unbalanced tires can also cause cupping, but the cupping would typically be more indicative of a concentric pattern. Shocks and struts are the most likely culprit because they provide damping force to control tire movement. When the tires move excessively, the scalloped pattern can appear. A lack of rotation can cause this condition."
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Old 02-16-2017, 03:58 PM
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Thanks. I had a local Jeep dealer today go through the whole front end. He claims all is good. I went back to the tire dealer and he balanced all the tires and moved the ones with no cupping to the front. We have been rotating at least every 5k and this issue just cropped up recently. Since it is always the left front he is positive that it is the shock. He has seen this many times and says that it is difficult to really test the shock. I also decided that it was not worth messing with an ordered two new front shocks from Quadratec. I will post more when I know more. Very nice article posted above and thanks for all the help.
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Old 02-20-2017, 02:51 PM
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Quadratec was fast shipping the shocks. Got them installed today. I will update this post after a few thousand miles. BTW - the old shocks seemed quite weak after only 40,000 miles. More to come...
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Old 08-08-2017, 12:28 PM   #9
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Quadratec was fast shipping the shocks. Got them installed today. I will update this post after a few thousand miles. BTW - the old shocks seemed quite weak after only 40,000 miles. More to come...
So, has it been a couple thousand miles yet? Just curious what you've discovered.
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Old 08-09-2017, 12:31 PM
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All is good. No tire cupping on my old tires or on the new tires and wheels. It was a bad shock in my front left side.
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Old 08-09-2017, 01:21 PM   #11
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All is good. No tire cupping on my old tires or on the new tires and wheels. It was a bad shock in my front left side.
I just saw this today but would have verified the shock theory ----- cupping is almost always from under-dampening the rebound.
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