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I have had two sets of tires cup. I thought the first time it was because of not rotating them early enough (about 3500 miles). So with the new set I've been doing it at 2000 miles but they still cupped. What's the story?
How often do you all rotate tires?
 

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I rarely rotate my tires, too lazy. The tire pressure may be off. The tires you have work great on the size wheel you run. My firend used to run a similar setup (3" lift, Q78/16 on MT Classics 16x8) and did not see cupping that I know of.
 

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I figured that I shouldn't have to rotate them very often. I keep 36psi in all four. I got that number from Mark F. with Bad Monkey. They max at 40psi. Could it be bad alignment or tires out of balance?
 

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Tire cupping is usually caused by worn ball-joints...
Over inflation would just cause the tire to wear more in the center of the tread.

I've got an older set of bias TSL's that have never been rotated in the last 10,000 miles, seen a ton of freeway miles and are not cupped. When my balljoints needed replacing I noticed because within 3000 miles my General Grabber MT's got all cupped.

Jack the front of the truck up and try and pull the bottom of the wheel outwards...I had 3/4" of play at the bottom of the tire. There should be no perceptable amount of play if the balljoints are good.

Rene
 

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tRustyK5 is correct. Bad balljoints will cause tire cupping.

On most vehicles grabbing the tire from the top and bottom (while that tire is in the air) and rocking it will indicate a bad balljoint or not. Ideally no play is the best, but 1/4" is acceptable within most factory specs anything more and I'd replace the ball joints.

Another thing to check while you have the tires up is your wheel bearings, for this rock the tires side to side. Again a little play is acceptable, but nothing drastic. Also look behind the tire when you're rocking the tire to check your tie-rods. Might as well as long as you have it up in the air.
 

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Bad alignment could be a possiblility. Take it to Sears, they'll hook your car up to the alignment machine and check it for free (atleast they do at my store, I check alignments all day long). If they do or aon't do that tell them you want a front end inspection. Those I know are free, they'll bring your truck in lift it up and check your balljoints/bearings/tierods/idlerarm and all your other front suspension parts. Its worth the trip to your local Sears store.

-Chris
 

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Okay...BRAIN FART <IMG SRC="/board/images/smilies/icon_confused.gif"> ...Im pretty new to owning big off road tires...what exactly is tire cupping? Is it earlier wearing of the inside or outside of the tire??? <IMG SRC="/board/images/smilies/dunno.gif">
 

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Premature wearing of the middle of the tread is because of over inflation typically, but also could be from "cupping". Cupping occurs commonly with larger tires (bigger than stock) on rims that aren't the optimum width. Take me for example, my 35X12.50X15 BFG A/T KO's are mounted on 15X8" rims... the optimum width rim for these tires is 10" wide. So having 15X8" rims is causing the sidewalls to suck in on the rim, ballooning the tire outwards which causes the tires to look like a 1/4 moon (when viewing front to back on the tire, not from the sides) as opposed to being flat.

Wear on the edges of the tire is normally from low tire pressure (the tire is riding on the sidewalls instead of the tread itself). Back to my truck... in my case because of running 15X8" rims if I run the tires with 32psi in them they will cup, so for around town I run 28psi (helps a little) and when I go offroad I go down to 15-20psi. However on the highway I like to keep it at 32-35psi so the truck will be more responsive.

Hope that helped a little, let me know if it didn't and I'll try to reword it.

-Chris
 

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Ball joints. A while back I was starting to see cupping on my tires. I checked my ball joints and what do you know they were worn out.
 
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