springs or struts?

Discussion in 'General Automotive Questions' started by burninbush, May 25, 2018.

  1. burninbush

    burninbush In Maximum Overdrive

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    So here's a question for the sages -- my 2004 Chrysler Concorde rides like it almost has no springs, seems like all 'give' in the suspension is coming from the tires themselves. Otherwise, there are no wear issues, tires last forever, steers straight without pulling.
    The car has 115k miles.

    It is obvious looking at a side view of the car that the springs hold the car at an original height, no sagging visible at all. Seems that it must be due to either the springs have somehow lost their 'spring' without sagging at all, or maybe the struts have gotten stiff somehow? Are either of those possible? This is my third Chrysler, no issues at all with the other two cars.

    If you take it to a shop to fix it, which parts do you tell them to change?

    TIA for any useful help.
     
  2. ForistellFord

    ForistellFord In Maximum Overdrive

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    It is possible that you are just a very old man with a creaky old body that is more sensitive to everything these days. But heck, you know that.

    It's likely that the shock is worn and compressing the springs a bit, giving you the stiffer feel. You don't get the bouncy-bouncy bad shock ride at all?
     
  3. plumcolr

    plumcolr In Maximum Overdrive

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    Ties over full?
     
  4. ribald1

    ribald1 Banned PLATINUM MEMBER

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    Strut seizing is possible, but happening to both sides at the same time is more than a bit unlikely.
    If you push down on the bumper, does the car go down, or seem solid?
     
  5. burninbush

    burninbush In Maximum Overdrive

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    Tires are normal 35psi.

    I only weigh about 170, and can't make the car jounce hardly at all. Ribald, are you suggesting springs? That seems most likely to me, but I'd hate to change them and find out it should have been the struts. Not a new problem, has been getting worse for maybe a year, just trying to get up my nerve to go to the shop.

    If you drive the car on a smooth highway there is no evidence of any problem. On bumpy street roads its a panic.
     
  6. ribald1

    ribald1 Banned PLATINUM MEMBER

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    Actually I suspect the rubber isolators on the strut assembly, but I wanted to rule out seized struts.
    Springs do get stiffer as they work harden, but they also uncoil, making them shorter.
    Have someone pull a wheel and inspect the isolators. They are rubber disks 3-5" in diameter that the strut bracing pass through. The disks may or may not be solid. If the support is not in the center of the disk, it has failed.
     
  7. 1978GT

    1978GT In Fourth Gear GOLD MEMBER

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    You should not tell them which parts to replace - just tell them what the symptoms are. Leave the diagnosis to the pros.
     
  8. ForistellFord

    ForistellFord In Maximum Overdrive

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    You have a 14 year old vehicle and I assume the original struts. It is time to replace them anyway my man.
     
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  9. Kiwirancher

    Kiwirancher In Second Gear

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    Would it be a reasonably easy thing to disconnect a strut ( shock absorber? ) then give the car a bounce ? That would tell you if the spring is ok or not. Doing this at each corner should tell you what is happening.
     
  10. ribald1

    ribald1 Banned PLATINUM MEMBER

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    As the strut holds the hub in place, no.
    If the spring is separate from the strut you could do that with a floor jack though, but it would be a fair amount of work for naught as springs don't become solid.
     
  11. burninbush

    burninbush In Maximum Overdrive

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    I don't see anything wrong with the struts -- they are turned from lock to lock just getting into my driveway, don't feel any different from new. I still think it's the springs, just can't quite accept the idea that they'll go much stiffer than normal without losing any height. This is a 2004 car -- the springs are much stiffer than on my 71 Ranchero.
     
  12. TestDummy

    TestDummy In Maximum Overdrive SILVER MEMBER

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    Springs don't get stiffer. They lose memory and sag, just like many other things do when they get old.
     
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  13. ribald1

    ribald1 Banned PLATINUM MEMBER

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    The struts are the things that look like shock absorbers, a shock absorber is part of the strut. The spring will be either around the strut, or behind it.
    The steering moves the hub at the end of the strut, not the strut itself.
     
  14. 5.0 Chero

    5.0 Chero MODERATOR Staff Member

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    BB replace the struts front and rear as FF says its time, springs do not get stiffer ride with age they soften with age unlike grumpy old men

    Not on a McPherson strut suspension the steering pivot point is at the top of the strut assembly second pic is a Concord front strut assembly

    upload_2018-5-27_2-4-55.png upload_2018-5-27_2-7-21.png
     
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  15. ribald1

    ribald1 Banned PLATINUM MEMBER

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    I had forgotten about those. There must be at least 90 different strut setups out there.
    A spring does get harder with use. It work hardens, like most metals do.
    Due to the way the levers are set up, a worn spring may appear to be softer. A leaf spring is a good example, as when it unwinds the lever becomes longer and the force angle more perpendicular, making it easier to bend the spring. That is why an arched spring feels stiffer than an identical spring that is not.
    Developing a spring that does not get harder with use would be a great thing as it would end the situation of springs breaking with age.
     
  16. Jimbob

    Jimbob SITE SUPPORTER- SILVER GOLD MEMBER

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    I changed my rear struts last year on a 95 new yorker. As others said,they get softer especially once the shock wears out, my car got real bouncy. It firmed up a bit once I installed new ones.

    Unless you are in a dry climate, you will have fun getting the rear strut detached from the hub also.
     
  17. Basstrix

    Basstrix In Overdrive BRONZE MEMBER

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    Work hardening, by definition, requires that the material is strained beyond its yield stress (plastic deformation). If you've ever bent a wire coat hanger back and forth to get it to break, you've experienced work hardening followed by low cycle fatigue. You can bend that same coat hanger back and forth all day long if you don't bend it beyond it's yield stress. Eventually, it will break, but it may take millions of cycles...this is high cycle fatigue. High cycle fatigue is often responsible for broken valve springs, rocker arms, con rods, etc.
    It's a common misconception that hardening a material significantly changes its stiffness. Stiffness (Young's Modulus) is relatively constant for a given alloy at a given temperature. Hardening allows the yield point to be extended farther up the stress-strain curve. I say relatively, because there are minor changes with some types of heat treatment.
    Springs under constant load tend to sag over time due to creep. Cyclic loading that exceeds the yield point, or comes very close, will accelerate spring sagging (and if yield point is exceeded, work harden).
    In all likelihood, your struts are locked up or binding. Try jacking up the car and observe how much suspension travels before wheel lifts off the ground. You should get at least a couple of inches before wheel lifts and travel should be smooth and correspond directly to upward movement of the car.
     
  18. handy_andy_cv64

    handy_andy_cv64 In Maximum Overdrive SILVER MEMBER

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    If the struts are at fault, he can simply measure the car's ride height, but admittedly, it's not 100% conclusive. He could have good ride height, but the struts are still locked up. I'm just hoping he'll find a height anomaly so he doesn't have to jack it up.
     
  19. ForistellFord

    ForistellFord In Maximum Overdrive

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    In other words, like we said, after 14 years your struts are ready to retire. Do it while you can still drive so you can enjoy the last few months on the road.
     
  20. ribald1

    ribald1 Banned PLATINUM MEMBER

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    As a person who hardens and anneals alloys on a rather regular basis I can attest that hardening a metal makes it more resistant to bending. In other words, stiffer. I can bend annealed items with my Hossfield bender that my hydraulic benders would struggle with if left hardened.
    Also, a spring under a static load that is well under it's yield rating will not relax significantly over time. Modern skyscrapers and bridges attest to this as otherwise they would fail and fall. Also entire skyscrapers, the Transamerica tower as an example, rest the entire structure on coil springs with motion dampers to absorb energy from earthquakes.
    Also, work hardening occurs well below plastic deformation. That is why ultrasonic hardening works. Vibration hardening is a form of work hardening, the internal structural changes to the metal are identical.
     

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