Height adjustabillity and preload.

[odessy]

Been looking at adjustable rear spring seats and was wondering if by compressing the spring and preloading it are you going to encounter any negative effects?

Maybe a newb question but when the height of coilovers are adjusted do the top hats? move with the spring so the captive height stays the same?
Not quite sure on the design or how they actually work lol.

Do they require specific springs to match the adj spring seat?

[odessy]

Kinda confused about how they work... Are both the top and bottom adjustable so your not actually compressing the spring?

[slydar]

the spring doesnt get "compressed". the spring has a given weight on it. (whatever % of the car that corner supports) adjusting the spring perch just adjusts the ride height.

on a base height adjustable front coilover you are able to also control the stroke point at static.

does that make sense?

[odessy]

I think so....

For adjustable rears you have an adjustable upper and lower, not just an adjustable lower(compressing the spring)?

[slydar]

nope. rears like ajps its just an upper. but it doesnt push down on the spring. it pushes the car higher up off the spring (if you wind the spring perch down ).

coilover converted rear, the spring perch, if you wind it up, pushes the car up, via the spring, but again, it has no extra weight acting on it.

if you wound it up to the point of the dampener being topped out, and then further, then yes you are compressing the spring, but then the car will not being any higher. also the shock should never be topped out (well rarely).

take some time and visualize it. youll work it out if you think about it.

to answer your first post. winding your coilover up to the point where it is compressing the spring will have negative effects. you will have no positive travel (droop) you need droop. even more so for our bumpy roads compared to japan.

if you find youre need to do that, your coilovers are too short.

[odessy]

Yeah okay, makes more sense after some sleep lol. So essentially when you convert a front strut to a coilover all your doing is adding a height adjustable spring seat, still the same insert?

Also am I right in saying the spring stiffness is inversely proportional to the free height of the spring?

[marvis]

I think you need to do some more reading before you ask questions like this..

[slydar]

yes, thats all you do, except you also shorten the strut body to suit the insert and the stroke point/range you want the dampener at at your approximate ride height.

so for a normal ae86 coilover, you really only have a range of say 2" of height adjustment. this should be plenty for most people. stuff like greddy/HSD are base height adjustable, like most coilovers for other imports, so theyre different.

a spring is basically a peice of wire you are twisting. usually we talk about them being rated in KG/mm. you cant make them stiffer by preloading them, nor should you. each extra xKG compresses them an extra xmm.

[slydar]

I think you need to do some more reading before you ask questions like this..

yup.

as in my other post. go to www.club4ag.com read the whole tech ref. will give you all the basic knowledge you need.

[AJPS]

Also am I right in saying the spring stiffness is inversely proportional to the free height of the spring?

the pitch and the wire diameter are part of the equation

[odessy]

Well these questions were a result of my reading and things I was unable to find answers for/get my head around. Things make more sense to me when I pull them apart and can inspect them in real life.

That link looks good, had a quick skim through but will give it a good going over on the weekend.

What I meant in terms of spring height and stiffness was the effects of cutting the spring to make it fit the adj. perch, but I think I reasoned my way through this and google seems to have confirmed. Reduce the length by 20% (cutting off coils) will result in an increase in stiffness by 20%?