Question Tire cupping Information

Discussion in 'Maintenance' started by hetzler_l33, Mar 19, 2017.

  1. hetzler_l33

    hetzler_l33 New Guy

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    Interesting, but good to know. It's hard keeping them rotated every 3k being so busy but I've been almost on mark besides this last time being 700 miles past due. I have about 70% left give or take but with putting 10k on them in almost 7 months, I know they're not gonna last long. Been thinking about 305/55 Ridge Grapplers with 20x9s next
     
  2. duke

    duke i like interco

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    That's what women on the site say about swampers but here I am after Idk how many sets. Anyway, no amount of balancing or swapping around is gonna fix a cupped tire. They just have to wear back flat lol.
     
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  3. mb1500

    mb1500 GMFS Member

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    If you're driving down a crowned road in 'Murica (right hand side) if your alignment is biased to the right your steering wheel will have to be cocked to the left to go straight. Is this how your truck is?
     
  4. kids-at-711

    kids-at-711 Sexually identifies as a shopping cart.

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    Yup, is the same way in the left lane on the hwy, is slightly to the right to stay straight.
     
  5. hetzler_l33

    hetzler_l33 New Guy

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    Alright, just wanted to update and see what you gentlemen think: tires eventually stopped shaking the steering wheel although there is still a shake however it is not from the tires since my steering wheel doesn't shake anymore. It's perfectly still and a nice smooth hum to the tires. Had to have the shop re-align the truck 3 times due to their error, I have a spec sheet I'll include for your eyes to see after the last alignment. Let me know what you guys think about it.

    Also, I got a rotation and holy cow it's doing that damn shaking again. It's honestly unbearable because of how bad it is. Now I know it's the back tires that's causing this but how and why? It's so bad that my mirrors shake and it feels like the whole tire is bouncing like it's an oval. I want to rip off the weights they stuck on to see if that stops it.

    Still not sure why, I rotate them religiously...could they just be doing a bad balancing job? Or are the tires just bad eggs? I did notice they didn't line the valve stem up with the paint dot on the tire when they installed them, thought that was common practice when mounting a tire.

    FYI on the spec sheet, I did the front coilover conversion and it's sitting about .5" higher in the front and I don't want to lower it otherwise the shocks will be out of their ride-height range but any higher and I don't see the ball joints or CVs being happy. Probably doesn't matter but just wanted to let you guys know in case you see something odd and wonder why.[​IMG]
     
  6. hetzler_l33

    hetzler_l33 New Guy

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    Another note: the first 2 times I rotated my tires, I didn't have this issue. They were perfect. Only started after my third rotation and now the fourth is yielding the same results. Tires only have 13,700 miles on them with over 60% tread on them


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  7. mitchell0715

    mitchell0715 GMFS Member

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    could be bad ujoints or pinion angle causing the shake in the rear unless its something that changed with tires being rotated/balanced/alignment being done

    cupping can be too skinny of a rim, or too much air pressure in the tires. pretty common with oversized tires.

    it was happening at first, you just didnt notice it due to the amount of tread, happened to me too
     
  8. hetzler_l33

    hetzler_l33 New Guy

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    I don't think there's a shake in the rear, it's just the front because it shakes the steering wheel and also the ranch hand bumper I have on. You can see the bars of the brushguard part shaking when going down the road.

    I have a 17x9 rim and it's almost in the sweet spot of recommended rim widths for my tire. I'll admit they are oversized but not much, 33x12.5R17 (true dimensions: 32.9x12.68R17)

    You may be right but I think the balance weights may be affecting how the tread wears so when it comes to the front from the back, they don't have that all around wear since the rears don't turn. My old Terra Grapplers (285-70R17) never did shake that bad. There was a shake at highway speeds but it was fixed from replacing the front end.

    But how can you tell if the shaking is coming from the drivetrain? I get the part if there's shaking and it's not from the steering wheel but how can you pin point it?
     
  9. mitchell0715

    mitchell0715 GMFS Member

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    your tires just arent balanced well is what that is, i misunderstood and that it was a hop or something in the rear.

    the other option would be a bent rim but i doubt it, you'd notice it change locations when rotating the tires.

    cupping is normal, the shaking isnt. whats the air pressure at though? might need to drop it a little bit
     
  10. hetzler_l33

    hetzler_l33 New Guy

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    I think that's what it is too. U-joints and pinion is good, rock solid and zero free play on both ends of the driveshaft.

    Yeah the rims aren't bent because it's not a constant. After 2k miles or so the tires will balance out but there is still a shake present, it's just not shaking the steering wheel.

    The front tires I usually keep around 35psi just so the wear is even and the rear is 30psi. The max psi is 65 and they are 10 ply.

    Like you said, I think the balancing job is crappy. I'm going to clean off the rims really good and scrape off debris to see where that gets me
     
  11. mitchell0715

    mitchell0715 GMFS Member

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    that's what i keep mine at, 35 front 30 rear. cant really go much lower for load range e gets dangerous.

    just a poor balancing job, oversized tires with any aggressive tread can be hard to balance, i bought the lifetime balancing from discount tire for that reason. try to get them balanced on a roadforce machine and see how that goes.
     
  12. kids-at-711

    kids-at-711 Sexually identifies as a shopping cart.

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    No, cupping is not normal. Tire cupping is mostly caused by bunk balancing.
     
  13. Coveman

    Coveman New Member

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    Ive experience cupping on two separate occasions. First was worn pitman and idler arms (the idler especially on GMT400s with 4x4, its a common wear item). Second was when i reversed the rotation direction of tires. I can only say that reversing rotation must have been invented by tire salesmen, it seems to reverse and lift the grain of the rubber and create those cup flaps and then wear it back flat.
     
  14. hetzler_l33

    hetzler_l33 New Guy

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    When I rotate them it's the front go straight back and the back ones cross to the front. So I'm assuming it's because they're being cross-rotated.

    Haven't replaced pitman or idler arm but I don't see how that will be making my tires shake like they are. The tires that came from the back are what's shaking, the tires originally on the front were smooth before rotation. But I might as well replace the pitman and idler arm since I'm not sure when they have been replaced, wouldn't hurt.

    As for the shaking, it's not driveline related. It's either suspension or tires but like kids-at-711 and mitchell0715 said, I think the balance job is trash.

    Oh well, have quite a few things to get right but at least they're minor and manageable *touch hood* I figure I'll replace the pitman and idler arms when I redo my oil pan gasket since everything is out of the way


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  15. Phildirt

    Phildirt n. fil-dert.

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    Pitman can suck. I had to pull my steering gear box to get the pitman off.
     
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  16. hetzler_l33

    hetzler_l33 New Guy

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    I've been hearing horror stories about how they can be a PITA to get the pitman off, but it's not completely impossible. Figured I'd get it knocked out when I have my oil pan off and some extra clearance. I'll have to redo my passenger side front axle seal also because it's started leaking again.

    Biggest problem for me are both the wheel shake and the oil leak/consumption. It's been 1300 miles since my last oil change and it's already 1.5 quarts low.

    It's annoys me having to add oil so much but also seeing the oil trails and puddles on/around the pan. But hey, what's the fun in a perfect truck right?
     
  17. kids-at-711

    kids-at-711 Sexually identifies as a shopping cart.

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    thats alot of oil lol.

    Check the balance. Dont go replacing parts just because someone said they had a problem with theirs. Check them out before replacing them.

    Also wondering if you possibly have a bent wheel, seems like your issue is moving around with the wheels.
     
  18. hetzler_l33

    hetzler_l33 New Guy

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    Tell me about it haha

    Take it to another tire shop to have them check the balancing? I mean I've had this truck for over 4 years, put over 55k miles on it and the maintenance history is unknown. I've never replaced the pitman or idler arm but like you said, I was going to make sure they have free play before replacing. Not sure how but I'll search it up.

    Well on my last rotation it shook just as bad but after 2k miles or so it didn't shake the steering wheel anymore but there was still a shake from 45-however fast I went. It'll shake the front bumper and mirrors but not like I'm driving with square wheels, just enough to feel it and notice it. It's almost like a soft shake, it's not very violent like how it was when I first rotated them and now.

    But is there a way to have them checked for their balance and also make sure the rim is straight?
     
  19. Tim W

    Tim W Timbrage: Engage

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    have the shop put them on the balancer and spin the tires by hand, any retard tire changer will be able to see if its got a broken belt or high/low spots, and super aggressive mud tires have been known to change their behavior as they wear
     
  20. mitchell0715

    mitchell0715 GMFS Member

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    i was confused with the inside of the tire being worn more than the outside and thought thats what the term cupping meant, did some research and you're right that cupping isnt normal although i have seen it a lot more with more aggressive tires
     

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