By on July 2, 2014

John writes:

You recommended to one writer that he consider replacing the springs on his car (as well as all other wear items in the suspension). Other then the obvious broken spring or the car sitting of the spring stops, when and how do you evaluate the need for springs? Do you recommend stock setting or performance springs for replacement?

Thanks, John (Jag, Kia, Miata, Chev)

Sajeev answers:

The most obvious sign of a worn out coil spring is a super plush ride combined with a saggy ride height at any corner. Funny tire wear or an impossible to find groan could also be a sign of bad coil springs. If you drive on suspension punishing roads (Boston-like urban, or unpaved rural) and drive a vehicle that’s 5+ years old with 100,000-ish miles, odds are a saggy coil has sprung its last proper rebound.

This isn’t obvious like a leaky air suspension bladder puking out pressurized air, but metal fatigue is for real. Even when not felt: springs, much like headlight bulbs, go bad very slowly.

While shocks/dampers affect ride, they can’t do a darn thing if the springs collapse to the point of no return. A proper ride height check is good, or just measuring right height from left to right with a few fingers.  If one side has less space between your fingers, you just diagnosed the problem. (speaking from personal experience)

Fortunately there are quick fixes for many cars: something like Monroe’s Quick Strut saves you money (labor hours) or time (in your garage) as you replace both the shock and strut in one shot, cheaper than changing the strut itself. Nice.

Last question: stick with stock or go performance aftermarket?  That’s a personal preference for which you gave me zero personal insight.  I normally default to retaining the stock spring, as it has the correct rate to ensure a fine ride/handling balance and won’t bottom out when loaded with passengers/cargo.  It’s always the safe bet. But…

Bonus!  A Piston Slap Nugget of Wisdom:

When it comes to shocks/struts/dampers or whatever you like to call them, that’s a different story. Some of my favorite performing vehicles use stock springs with aftermarket shocks of the premium performance variety:  Koni or Bilstein for starters.  Most drivers need a stock spring (even if they don’t want to admit it) but they certainly want superior control over the spring’s up/down motion.  Aside from well sorted out performance cars, you’d be shocked at just how much better an OEM spring and performance damper work together to bring a big-ass smile to your face when hugging a corner or two. And that’s even more reason to stick with stock springs.

 

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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22 Comments on “Piston Slap: Bouncing Back or Sprung Out?...”


  • avatar
    CoreyDL

    And then when you do the shocks, it might not help much because the bushings will be all used up too.

    I really struggle with proper suspension management and maintenance. It’s all too questionable when you need to replace things.

    • 0 avatar
      bumpy ii

      My vehicle preferences run towards 20-year-old sporty cars, so full suspension bushing/bearing/etc. replacements are always on the table. The tricky part there is deciding on OEM-style rubber (you usually have to buy the entire piece) or stiffer urethane that can be replaced DIY.

      • 0 avatar
        racebeer

        I think the rubber/urethane decision depends on where you are using the car. For autocross, urethane is the way to go. BUT …. if you are not doing that very much and are mainly on the street, then rubber makes more sense. I’ve seen too may friends go to urethane route expecting a great enhancement to handling only to bitch and moan about all the suspension pounding and squeaks that get transmitted with urethane. I’ll admit I did change springs and shocks on my T/A (Sam Strano springs w/Bilstein HD shocks), but I retained the rubber bushings. The only exception was the panhard rod, which I replaced with an adjustable one because of the ride height drop (had to recenter the rear axle). One side is urethane and the other is a rotojoint to eliminate any suspension binding. I hear it every once in a while, but for the most part it is quiet.

        BTW, even my wife said the car felt “better” on the road with the spring/shock change. If you are careful in your choices, you can achieve a firm but not harsh ride with much improved road manners.

        • 0 avatar
          PonchoIndian

          racebeer
          I too did the shock switch on my 2000 T/A with the Bilstein HD’s, and even went with Sam’s recommendation of using the 3rd Gen F-body valving on the rear instead of the 4th Gen valving.

          What an amazing difference they made compared to the stock (new stock at that) decarbons that it had on it. It made the car much more pleasurable to drive and got rid of 99% of the rear axle after bump body wobble the stock suspension had.

        • 0 avatar
          raph

          racebeer said – One side is urethane and the other is a rotojoint to eliminate any suspension binding.

          UMI suspension stuff? I ran their real control arms and panhard rod on my Mustang, pretty good stuff but I found the rotojoints to be pretty maintenance intensive. I got them to last about two years before having to replace the joints (ended up trying different arms in the end) although I still run the UMI panhard rod. The rotojoint is very well protected from the elements so no issues there.

          I liked the freedom of movement offered by the rotojoint equipped control arms though.

  • avatar
    Fred

    One thing I notice about this question, and it’s popularity on various car forums, is the questioner rarely states WHY they want to make the change.

  • avatar
    319583076

    Springs aren’t wear items. Either they function or they’re broken and require replacement. Admittedly, in my own experience, it’s not always clear when a spring has broken and therefore needs to be replaced but a spring can’t wear out like shocks(dampers)can.

    Replacement shocks should remain identical, or close to, OEM shock specifications in order for the suspension to work properly.

    • 0 avatar
      PonchoIndian

      Replacement shocks should remain identical, or close to, OEM shock specifications in order for the suspension to work properly.

      I think you’ll find many people will disagree with this comment. Myself included.

      Shock/strut rate changes can do more for a car’s personality than just about anything else. The factory specifications are often a compromise. Even the cheap replacements from a brand like Monroe have higher rates than the stock specifications to compensate for other worn items in the suspension.

      • 0 avatar
        319583076

        All specifications are a compromise, there is no-free-lunch. The OEM spring damper tune has more money, research, and design to support it than the aftermarket and certainly more than simply swapping some different shocks onto your vehicle.

        The suspension performance will change with mismatched springs and dampers, but not necessarily for the better and likely any improvements in one area will be offset by compromised performance across the board.

        If you have the resources and motivation to optimally tune your car’s suspension for whatever sort of driving you’re interested in, you can probably do better than the OEM setup. If you are just swapping in some different shocks with the OEM springs, you’ll likely end up with a net loss of performance from the OEM setup.

    • 0 avatar
      MBella

      Like Sajeev said, springs do fatigue and start compromising the handling of the car. My Sentra used to sit a bit lower on the passenger side until I swapped the front struts.

    • 0 avatar
      Brian P

      I don’t agree with “stay stock” as a general rule. Occasionally one will find a car with good stock suspension calibration, but more often than not, the stock dampers will have internal valving that was built to a price.

      What is important, though, is that any choices made be properly matched to each other.

      Faced with sagging springs and worn-out struts on my own car, and knowing that the stock components were built to a price, I opted for a complete Bilstein coil-over kit, figuring that Bilstein would have done their homework with the spring and damping rates. They did. This completely transformed the car … and although the ride is unquestionably firm, it’s manageable – and certainly better than bouncing off the bump stops, which the stock cheap dampers and too-low spring rates were prone to do.

      • 0 avatar
        319583076

        The sole point I’m trying to communicate here – and forgive me if I’m doing a poor job – is that springs and shocks work together.

        If you’re just replacing your shocks and retaining your springs, I think you should retain the OEM shock specification because the shocks and springs were designed as a system. Altering one component of that system without consideration of the total system performance will likely negatively impact suspension performance.

        If you’re going to a coil-over system (i.e. self-contained shocks and springs), or you are replacing both shocks and springs, you have as many options as you can afford among the combinations available in the marketplace. Obviously, you have the power to change the suspension performance in comparison to the OEM setup.

        OEM dampers are built to a price, but they are also matched to OEM spring rates to provide suspension performance within the OEM envelope. Buying expensive shocks and installing them with OEM springs does not automatically correlate to improved suspension performance.

        The whole point here is – your shocks and springs work together.

  • avatar
    OneAlpha

    It’s time to replace your springs if Speedhunters wants to do a feature on your car.

  • avatar
    PonchoIndian

    Springs fail in two ways. They break and they “sag”. The “sag” does not change the spring rate however, so the only difference you would feel in ride would be hitting the bump stops harder because you don’t have as much suspension travel.

    A secondary effect of the decreased ride height from a sagging spring would be the inability for a shock to control the suspension as effectively at the lower ride height. The shock/strut is designed to control the suspension movement from the original static ride height. Raise or lower the ride height and the shock/strut no long has the same control as it was intended to have. That is one reason why you see all the lowered Civics bouncing down the road. They cut the springs but kept the stock shocks.

    Another thing to remember. Don’t measure ride height using the fender lip. There can be greater dimensional differences than you might think in the cosmetic panels side to side. Use a chassis point like the jack location on the rocker panel.

  • avatar
    bachewy

    Reminds me of the 2000MY Ford Focus. They welded an extra ring to the front springs on those cars, covered by a rubber boot, in order to compensate for the heavier engine used in the US (compared to Europe). Those welds would break after a few years with Ford claiming it was due to salted roads causing corrosion and spring failure. That year had 13 recalls that didn’t include stuck throttles which quietly occurred (no press coverage) as well by bent throttle cable brackets from the factory.

    Yeah I had one. Rant over :)

    • 0 avatar
      18726543

      Aww, I remember this! A friend of mine had an ’02 Focus ZX3. The driver’s front spring broke and the broken spring poked through the inner sidewall of the tire while she was driving, slicing the tire open like a tuna can!

      Ford had trouble with rear springs on the Taurii of those years too. Seems like most of the ones I see still driving around look like they’ve got a hippo stuffed in the trunk.

  • avatar
    wstarvingteacher

    Well mu 4Runner has a saggy butt (as they all seem to do if they are used much) and I know exactly when I’ll change things. When I have the money in the bank.

    Haven’t made up my mind what corrections to make but a trailer figures prominently so it will happen. I expect the forums will figure into my solution.

  • avatar
    JuniperBug

    Regarding the Miata, specifically, it’s a bit of a different animal than some other mainstream cars – namely very short travel, much reliance on bump stops over bumps and in cornering, and a very adjustable, capable chassis with a lot of potential.

    Many claim that going to stiffer springs can actually improve the ride quality of the car. What’s important, though, if you’re going to aftermarket springs, is not to go lower unless you go much stiffer; there’s simply not enough travel. And if you go stiffer, you need a quality (read: expensive) shock. Bump stop selection is also important. Personally, I went with the only well-regarded Miata lowering spring that I know of for the NA/NB: Flyin’ Miata. They drop less than an inch and are just under double the spring rate. You don’t want them on stock shocks, but I’m pretty happy with the result when paired with Tokico Illuminas.

    I think it’s important to point out that suspension tuning is a black art. You’re much more likely to find happiness by using a tried-and-true formula for your specific car than to pseudo-engineer a setup together yourself. And even what may work well for one car, may be garbage for another. Example: Civic guys love the Tokico HP, while on Miatas they’re regarded as garbage.

  • avatar
    -Nate

    .
    ” I think it’s important to point out that suspension tuning is a black art.”

    Boy howdy you said it ! .

    I tend to have non Sporting Motor Vehicles (avatar etc.) that I then want to drive waayyy too fast so as soon as I can I replace the shocks with Bilstein HD’s , even SWMBO’a old Mercedes Sedan got them and she’s well pleased with them .

    Me OTOH , I want a firmer ride and so often replace the springs with heavier ones but never lowered as I drive a lot on bad pavement , off road , over RR tracks etc.

    I like the firmed up ride quite a bit but SWMBO no longer likes riding in my avatar car as is makes her ” wiggly bits ” bounce too much ~ I don’t notice , everyone else says it goes too damn fast .

    It too has red polyurethane suspension bushings now .

    =8-) .

    -Nate

  • avatar
    Tinker

    I bought a new 1997 F-150, that had a horrible ride, When I’d make a turn from the highway into the subdivision, the change in road level (the drainage channels are particularly deep along this road) gave the cab a HUGE thump, and I couldn’t decide whether it was the tires or the shocks. So I took a chance and replaced the tires. Nope. A few months further on I installed Edelbrock lifetime shocks, and that cured the problem. Seems the OEM valving did not allow the tire to stay in contact with the road surface. The Edelbrock valving was soft enough under full droop it really improved the ride. Made my year…

    • 0 avatar
      highdesertcat

      Shades of my 2006 F150!!! I had a similar experience. Cured mine by putting on four Michelin tires and Rancho Long-travel Gas shocks. Cured everything that ailed the ride.


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