Plop plop sound from tires - but not a flat!

Discussion in 'Gen 3 Prius Main Forum' started by JBarleycorn, Jan 22, 2020.

  1. JBarleycorn

    JBarleycorn Junior Member

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    Driving my 2012 Prius this morning I heard a plop-plop-plop sound from the rear. It starts at around 12-15 mph and speeds up as the car accelerates. It sounds *exactly* like a flat tire. But when I look at the rear tires I see nothing wrong. Tire pressures are at specification.

    The tires are Goodyear Assurance FuelMax installed June 2017. They have about 24000 miles on them.

    Any thoughts?
     
  2. Nor'easter

    Nor'easter Junior Member

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    Something stuck in the tire or tread?
     
  3. ASRDogman

    ASRDogman Senior Member

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    Is there a nail or screw in one tire? Wheel bearing? Warped rotor?
    Could be a few things. Drive in a parking lot and have someone along side and look and listen....
     
  4. fuzzy1

    fuzzy1 Senior Member

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    Have you inspected the entire circumference of the tires to discover any possible foreign objects lodged in the tread?
     
  5. ILuvMyPriusToo

    ILuvMyPriusToo Active Member

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    If it isn't something in the treads, once I had a stone in the metal hub that would drop and sound like that as the wheel turned at slow speeds. It finally fell out (and I found it - pea sized only), but I did a lot of head scratching before that because the treads were clean.
     
  6. JBarleycorn

    JBarleycorn Junior Member

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    I didn't see anything in the tread, but I need check again in better light.

    What would be the indication of a warped rotor?
     
  7. Grit

    Grit Senior Member

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    Tire probably bulged on the inside, had that happen to me before. Tires were about 7 years old at the time and I scraped the cement bump thing at the store parking lot that tells you to stop pulling forward in the parking space.
     
  8. Pluggo

    Pluggo Active Member

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    If the sound goes away by itself, it may have been a flat spot from being parked too long. It happens.
     
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  9. bisco

    bisco cookie crumbler

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    rotate the tires and see if the sound changes
     
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  10. Robert Holt

    Robert Holt Senior Member

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    I will add a possibility: You may have the beginning of tread separation between the outer layer of the carcass or belts and the inner layer of the carcass. You usually cannot see the bulge at rest, but when moving the separating spot flies outward a bit and then flops into the pavement as it comes down , causing the “plop” sound. If that goes on for a while you may see a slightly more worn spot in the tread where it is plopping against the pavement, but it is extremely dangerous to drive a tire that is having carcass layer separation as the stress at highway speeds can cause a sudden total separation and blowout. That has happened to the car I was driving and to a semi driving directly in front of me. In both cases the tire throws chunks of tread and the belts out in all directions and then the carcass explodes as it is too weak to hold the pressure. Please have it checked.
     
  11. ASRDogman

    ASRDogman Senior Member

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    A wheel weight might have come off. Are they stick on ones?
     
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  12. xliderider

    xliderider Senior Member

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    I'm also leaning toward this theory/guess. The bulged sidewall on mine was on the inside sidewall,never knew it was there till the tire shop told me it needed to be replaced.

    Posted via the PriusChat mobile app.
     
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  13. Robert Holt

    Robert Holt Senior Member

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    That’s a possibility, but for me losing a tire-balancing weight has resulted in a weird vibration that would maximize at some lower speed like 30, but then decrease until hitting a higher multiple of that speed like 60 where it would increase again. So the vibration would not increase linearly with speed like the tread separation “plop” thing tends to do. That said, when you have two dynamically out-of-balance tires in the front, they can get “in phase” with each other at certain speeds , and in the Mazda I had with that problem the steering wheel would rather quickly shake so violently that car would become essentially directionally uncontrollable—very unpleasant.
     
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  14. bisco

    bisco cookie crumbler

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    a repetitive scraping sound as the rotor and pad rub
     
  15. ILuvMyPriusToo

    ILuvMyPriusToo Active Member

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    And it should pulse the brake pedal if you stop on mechanical brakes (switch to Neutral before you brake lightly),
     
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  16. JBarleycorn

    JBarleycorn Junior Member

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    Thanks for interesting suggestions.

    I was hoping it was a flat spot on the tire, because it first happened on a very cold morning after I hadn't driven for a couple of days. But the sound is still happening so I don't think it's a flat spot.

    I don't hear any odd sound or feel any pulsing in the brakes, so I don't think it's the rotor. The car doesn't pull to right or left, and there's no vibration at highway speed. Not sure how to check the wheel weights ... It sounds awfully loud for a wheel weight.

    I guess I will rotate the tires around and see if anything changes, and/or look at the wheels while someone drives around in a circle. Then I guess I'll have to take it to a shop ...
     
  17. wjtracy

    wjtracy Senior Member

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    I had some Goodyears that made a sound but there were pretty old. I tend to not rotate tires so they can stay on the rear without much wear for a long time.
     
  18. jburg

    jburg Junior Member

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    I would check the play on your hub bearing. Jack up the car and see if there is play in the wheel. I would put money on that.
     
  19. lenjack

    lenjack Active Member

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    wheel bearing?
     
  20. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Maybe pop the wheel off and have a real close look.
     
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