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Adjustable Front Strut Conversion

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    Adjustable Front Strut Conversion

    This article will cover how to convert your front struts (which are already a coil-over style) to an adjustable front strut. The benefits of this conversion will allow you to adjust the suspension height of the front end, facilitate easy spring changes to a softer/stiffer spring, and you will no longer need a spring compressor to service the front strut assembly (as you can simply run the adjuster nut to decompress the spring until it is unloaded).
    I recommend building a new set of front struts on the bench before you even take a wrench to your car, minimizing the vehicle’s downtime.
    The FWD A-body front struts have a 6.5 inch stroke for suspension travel so it is critical that you purchase a coil-over spring which is properly rated for at least a 6.5 inch usable stroke. For this build, a 2.5inch inner diameter coil-over spring with a 10inch free length were used. This keeps the new spring up high like the OEM spring, maintaining clearance for wider wheel/tire packages. It is critical that you perform your due-diligence in purchasing a spring from a retailer that lists Usable Stroke (inches), Max Stroke (inches), Spring Rate (lbs/inch), and Maximum Load (pounds). The science of coil springs is beyond the scope of this article, but the lesson is this: if you buy Chinese-made coil-over springs from Fleabay, don’t whine about poor suspension performance or blame other components for a harsh or uneven ride. Some of you may comment that variable rate coil-over springs could be used for an initially soft ride that gets progressively stiffer. While this is true in theory; in the real world variable rate springs are inconsistent in replicating the supposedly progressive spring rate they claim from spring to spring. Simply test two progressive springs on a spring dyno and graph the variance of force between two springs as you compress each one the same amount throughout each spring’s usable stroke. I recommend selecting a linear rate spring for your application. For this build on behalf of user Drop Top Olds, his Celebrity will receive Swift Springs.

    How do I choose a spring rate?
    Years ago when I first did this conversion, I took my turbocharged Cutlass Ciera to a trucker’s CAT scale. You won’t get corner weights, but you can get front and rear axle weights using the scale. Talk to the attendant and explain what you’re trying to achieve. They’ll tell you where to park on the scale. My seriously stripped down car came in at 2920 pounds with myself in the driver seat and a full tank of fuel. The front came in at 1860 pounds and the rear at 1060, resulting in a 63/37% weight bias. For this car, I ran 225 lbs/inch springs for the front. As a point of reference, the OEM front springs are rated at a paltry 85 lbs/inch! Rear OEM springs are rated at 162 lbs/inch. I was satisfied with the ride characteristics of my spring choice. For Drop Top Olds, we’ll be starting with a 185 lbs/inch spring. The beauty of this modification is you can easily swap out springs in an afternoon on the bench and you don’t need a spring compressor to do it! I recommend starting with springs at 185 lbs/inch and working up from there. Each person will have their own requirements for ride quality (so will your passengers).

    Okay, so what components do you need to get started?
    (2) Front struts (choose your favorite brand)
    (2) Front upper strut mounts-Moog (K6446)
    (2) Upper Spring Caps-QA1 (QA1-9018-101)
    (2) Polyurethane Bump Stops-Allstar (ALL64329)
    (2) Lower bearing kit for 2.5inch spring-Allstar (ALL64210)
    (2) Adjustment Sleeve 7inch-A1 (A1-12455)
    (2) Adjustment Sleeve Nut-A1 (A1-12460)
    (2) 2.5inch ID. Coil-Over Springs with a 10inch free length
    (1) Adjustment Wrench-Pro Shock (Z902)

    The hardest part is first. Begin by mounting your strut in a vise and wrapping gaffer’s tape over the strut rod to protect it. Use a cutting tool (like an angle grinder) to cut off the lower spring perch reinforcement which has two small weld points on the strut body. Take extra care and patience to not heat up the strut body as this may warp the strut chamber and irreparably damage it. Also take care to not grind away material from the strut body, as this directly weakens it.

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    From here you can see the weld point for the lower spring perch. Patiently cut the weld away so the spring perch is separated from the strut body. Use a flap disc on an angle grinder to grind off the remaining weld and to restore the originally smooth surface of the strut body.

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    Mask off the strut and paint the exposed metal with some paint to protect the strut from rust. Allow to cure, then remove your masking material. Once the paint is dry, the 7inch coil-over sleeve should simply slide right onto the strut body. Thread the adjustment nut towards the bottom of the strut and place the 2.5inch bearing kit onto the top of the adjustment nut.

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    You’re now ready to install the bump stops. Simply work them on by hand. These are a low-durometer polyurethane which simply ‘grab’ the strut rod and ride just underneath the QA1 spring cap & upper strut mount. These serve as a safeguard to prevent permanent deformation or damage to your suspension components if you happen to find a large pothole. They are absolutely necessary!
    Now simply place your spring onto the bearing and adjustment nut, then place the QA1 spring cap on top of the spring. From here, the OEM upper strut mount should easily install. Using your hands, adjust the adjustment nut up so the spring is barely loaded and the assembly stays together without clinking about. At this point, you have a complete strut assembly which is ready to be swapped onto your FWD A-Body.

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    [I will not cover the removal or installation steps of the front struts. If you are not familiar with this process, reference your Factory Service Manual.]

    Once your adjustable struts are installed on the car, you will now have to experiment with the adjustment nut to achieve your desired ride height. Make sure the car is sitting on level ground when you do this. If you’re lazy, you can simply take a tape measure and measure from the ground to the top of the front wheel arch. I suggest measuring from the ground to the engine/transmission cradle directly between the two lower control arm bushings instead. Mark your reference point with a paint marker. By referencing the chassis and not the body, you will make more accurate measurements each time, meaning you will make finer chassis adjustments.

    Once you take your ride height measurements and compare that to how you want the car to sit, you’ll decide to either raise or lower the car. To adjust the ride height, jack up the car with a floor jack and support with jack stands. Remove the front wheels and use the adjustment wrench to move the adjustment nut up or down. Then reinstall the wheels and put the car back on the ground. Jounce the suspension at all four corners to get the car to rest normally, then remeasure your ride height at the front. You’ll have to do this two or three times, but it will be the most fun of the entire ordeal. When you achieve your desired ride height, be sure to tighten the small allen screw that is on the adjustment nut. This will lock the adjustment nut to the adjustment sleeve and prevent the ride height from getting out of spec. Perform a final check to validate that everything was properly reinstalled. Now, go out and take a very short test drive. Listen carefully for any suspension pops. If the car passes this test, go and have an alignment performed as soon as possible. Since the struts were removed and installed, the camber and toe settings would have been disturbed. I recommend a camber setting of -0.5 degrees with a toe setting of 0.00 to 0.01 which is a very slight bias to toe-out. Recheck your ride height after the alignment, if your camber was way off, the ride height may have been affected when the alignment got everything back in spec. Finally, at this point, you can go out and drive in true spirit. Good luck and happy motoring!

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    What is this & what does pulling it out do?

    #2
    Most Excellent. Front Coilover conversion with Addco rear sway bar should really make this a corner carver. Your work is always top notch. Many Thanks!
    1959 Chevrolet Apache 31 235 I-6 SM420
    1971 Oldsmobile Cutlass Supreme Conv 350-4 V8 THM350
    1988 Chevrolet Celebrity Eurosport 2.8 V-6 Getrag 5 Speed

    Comment


      #3
      Wonderful write-up!!!

      I know we discussed it in the past, but I'm still liking my -1.0* camber setting. I like the turn-in response it seems to provide and while I haven't really driven the car in a while, it doesn't seem to chew the tires off. There's probably 5k or better on the alignment and the wear isn't noticeable yet.
      -Andy

      '86 Eurosport VR coupe
      '86 Eurosport sedan
      '88 Eurosport VR coupe
      '89 Eurosport wagon

      Comment


        #4
        Thank you both for the kind words!

        86euro, I recommended a -0.5 camber setting as a general target for all audiences, not knowing what their wheel/tire package may be. By my recollection, I ran -0.8 degrees of camber on my turbocharged manual Cutlass Ciera and found it to be reasonable with 16inch steel wheels. Unfortunately I do not recall the tire size/width. In this picture, the car had a full payload in the trunk and interior. Note how the rear is squatting a little bit with the OEM rear springs and Monroe #58427 rear towing/hauling shocks.

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        What is this & what does pulling it out do?

        Comment


          #5
          Took a 15 month break from us, and came back with that!

          Welcome back man.. Looking good!
          Brian - Carpe Diem

          I dont have to love my president, or any god, to love my country!!
          More people have died in the name of "God" than in all wars combined thruout history
          01 Pontiac Aztek GT AWD 127k - 04 GMC Envoy SLT XUV 193k

          Comment


            #6
            Great writeup. Something I might think about with my van some year.
            Jay

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