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Old 02-09-2010, 07:11 PM   #117
williaty
Scooby Guru
 
Member#: 71092
Join Date: Sep 2004
Chapter/Region: MWSOC
Location: Delaware County, Ohio
Vehicle:
2005 2.5RS Wagon
Regal Blue Pearl

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Quote:
Originally Posted by gagliano View Post
I don't see how you can say that. Mono adjustable coilovers require you to make height adjustments by changing the preload setting of the lower perch. If I add zero preload to the coil, the unit will sag thus lowering ride height. If I add more preload by moving the lower perch higher up the shock body, the vehicle will sag less and the ride height will be taller. The differing spring rates you mention will determine how much pressure is exerted against the perch as I increase preload.
Wrong.

With a single-adjustable coil-over, the main spring should be fully extended at full droop. On top of that, the helper spring should be mostly extended. This causes the springs to remain firmly seated. Due to the tiny spring rate of the helper spring compared to main spring, the main spring is compressed infinitesimally so long as the helper spring hasn't reached coil bind. As your raise and lower the lower spring perch, you are moving the main coil up and down without compressing it. The change in the distance between the upper and lower perches is being entirely accommodated by the helper spring compressing and expanding. Because of the helper spring, the preload on the main spring isn't changing at all. As soon as you set the car on its feet, the helper spring collapses and becomes solid. The main spring compresses slightly and the car settles to its final ride height. Because the main spring always compresses the same amount for a given car weight on it, moving the lower spring perch up and down results in the overall ride height changing.



Quote:
Then let me say it this way, dual adjustables make the changes by shifting CG to attain balance without making any changes to spring preload and sag; is this not better?
Neither singles or doubles change the preload. They're making the same adjustments to suspension geometry, CoG height, etc.

Quote:
Ohlins makes dual adjustable coil overs for our cars; can we agree that they make a quality product?
There is one advantage to dual-adjustable. If you're stroke limited, that is to say if the damper bottoms out before the coil binds, a DA setup can offer you slightly more height adjustability without sacrificing damper stroke. However, if you already have more travel in your damper than you do in your spring (which is easy to do if you use cheap springs), then there's no difference between DAs and SAs.
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