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Discussion Starter · #1 ·
Installing new custom coil adjustable coil overs on my Esprit.

I have to pre load the front springs more than 2" to get the ride height.

6" free length
325 lb/in spring - linear rate spring

Compressed to ~ 4 inches

I did some reading and I understand the spring rate does not change until you reach coil bind

but

if the spring is pre loaded 650 lbs (2 x 325) the "break away" force will be 651 lbs before the spring starts to move.

That seems like a very stiff ride.

So If I need 650 lbs to support the axle - why not just go with a 650 lb spring?

Obviously I am not understanding something.

But

I suspect I can go to a higher spring rate and it will result in a lower break away force and actually get a less jarring ride.

Anybody can explain?

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This video explains it well.
 
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Discussion Starter · #3 ·
Hmm thanks for that - looking at some additional videos, and this..

Preloading does not change spring rate but preload does change the force to start moving the shock and high preload dramatically reduces shock performance over smaller bumps and makes for a more harsh ride and worse traction. Spring rate is the force required to move a certain distance whereas preload adds a fixed force across the whole stroke. Heavy preloading can add over 100 pounds (45kg) of force required to start shock movement whereas optimal shock performance comes from the lowest starting force possible. Heavy preload means those smaller bumps won't even move your suspension.

Seems like high pre load would mean those expensive shocks dont get to do their thing. But maybe setting ride height is not the same pre load they are talking about?
 

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Discussion Starter · #4 ·
I think I have figured this out - its not a thing at all. Its just compressing the spring to get to the weight needed to support the car. A stiffer spring will have less pre load but a stiffer ride. I think I need a longer spring ideally but I believe these will work. I read that 25 to 30% compression is ideal. I am a little past that.
 

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I think I have figured this out - its not a thing at all. Its just compressing the spring to get to the weight needed to support the car. A stiffer spring will have less pre load but a stiffer ride. I think I need a longer spring ideally but I believe these will work. I read that 25 to 30% compression is ideal. I am a little past that.
I was going to say this, haha. Changing the collar height does not change the length of the spring other than a tiny amount due to shifting the corner weighting. If you are raising or lowering all four corners the same though, then you are just changing how the car sits relative to the spring and not compressing it any differently. Now, you will be changing the motion ratio a little (how much a spring moves relative to how much the wheel moves), and this will change the effective spring rate, but that shouldn’t be a big difference if you are within a reasonable window.
 
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