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Thread: Suspension preloading

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    Junior Member iammyowngod's Avatar
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    Suspension preloading

    Question, after installing lowering springs, do you need to preload the suspension on our mirage before torqueing the bolts? Ive read alot about it causing uneven ride height or not getting the desired ride height because the suspension was not preloaded before torqueing. Im not sure if it applies to our mirage. If it does, what would be the process for our car? Thanks.



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    Still Plays With Cars Loren's Avatar
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    On the rear, the only bolts you're loosening that secure something that could bind are the lower shock bolts. Not a bad idea to get the rear suspension compressed to static height before torquing those bolts. Easiest way to do it would be to put the rear up on ramps. If you happened to loosen the pivot bolts at the front of the rear axle, then those should also be torqued under static load.

    On the front, the upper mounts are free to rotate, no problem there. On the bottom, you're only taking the two strut-to-hub bolts out. There's no pivoting happening there at all, so nothing to worry about.

    IF you removed the lower control arms for some reason, the inner bolts on the lower control arm are pivot points that could bind if the bolts were torqued with the suspension at full droop.

    It's all pretty simple to understand if you just step back and look at it and think about how it works. What you're trying to avoid is torquing down a pivot point with the suspension drooped. If you do that, then that pivot point will bind and potentially hold the car up higher than it should be until either that bolt slips, or the bushing that is in-play wears in or breaks. It can be really bad for the bushings.

    I'm intentionally not using the term "preload" because that has a somewhat different meaning when you're talking about setting up height-adjustable spring perches. (but, I know what you're talking about)
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    Junior Member iammyowngod's Avatar
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    Quote Originally Posted by Loren View Post
    On the rear, the only bolts you're loosening that secure something that could bind are the lower shock bolts. Not a bad idea to get the rear suspension compressed to static height before torquing those bolts. Easiest way to do it would be to put the rear up on ramps. If you happened to loosen the pivot bolts at the front of the rear axle, then those should also be torqued under static load.

    On the front, the upper mounts are free to rotate, no problem there. On the bottom, you're only taking the two strut-to-hub bolts out. There's no pivoting happening there at all, so nothing to worry about.

    IF you removed the lower control arms for some reason, the inner bolts on the lower control arm are pivot points that could bind if the bolts were torqued with the suspension at full droop.

    It's all pretty simple to understand if you just step back and look at it and think about how it works. What you're trying to avoid is torquing down a pivot point with the suspension drooped. If you do that, then that pivot point will bind and potentially hold the car up higher than it should be until either that bolt slips, or the bushing that is in-play wears in or breaks. It can be really bad for the bushings.

    I'm intentionally not using the term "preload" because that has a somewhat different meaning when you're talking about setting up height-adjustable spring perches. (but, I know what you're talking about)
    Thank you man, great info. So if I never touched the lower arm bolt while installing the strut/lowering spring, I dont need to loosen it to clock/preload(not sure what term i should uae)? Will loosening the strut to knuckle bolts and torqueing it while the car is on the ground make any difference?

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    Still Plays With Cars Loren's Avatar
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    The knuckle bolts just affect camber if they have enough slack in them to do so. (and if you want more camber, you can slot those bolt holes and easily get some adjustment)
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    Quote Originally Posted by Loren View Post
    The knuckle bolts just affect camber if they have enough slack in them to do so. (and if you want more camber, you can slot those bolt holes and easily get some adjustment)
    Good info. My car has too much camber and the tires wear on the inside such that at around 30K miles I flip the tire on the rim to get somewhat even wear patterns. Other alignment numbers look good though.

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    Still Plays With Cars Loren's Avatar
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    Camber wear on the inside edge is surely a sign that you're not having enough fun.


    Simplify and add lightness.

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