If you are speaking of *adjustable* coilovers, it's easier
if you lift the car off the ground to get the car weight off the adjuster ring.
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If you are speaking of "coilovers", meaning what most import cars
have: "a coil over the shock", then lowering the car is more complicated,
and some measuring is needed beforehand, so the springs are not flopping around loose, the suspension is not getting beat up, and the tires are not being eaten.-Bob
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Be aware that when a car is lowered, the alignment changes. If you want it checked, get back with me. After an autocross, for example, when you raise it back up to clear the speed humps, you need to set the toe back
to what it was before you lowered it for the event.-Bob