Coilover Help. Am I doing something Wrong?

[Yasko]

I have a 1996 240sx w/ Stance Gr+ Pro coils. The problem is, is that the Back Right side is .5" higher than the back left. The front sides are exactly even. I have lowered the back right 1.25" thread wise and it only lowered it 1/8". The Preload is almost exactly even on both sides (not sure if that affects height or not).

I just don't know what I'm doing wrong. Is my frame bent or something? I get it inspected tomorrow then if it passes I'm going to get an alignment the next day. Maybe the problem is camber related or something.

It looks perfect from the front, but then when you look at the back it's very noticeable. It almost looks like a fat chick is in the drivers seat or something.

Any thoughts or ideas to why this is would be appreciated.

[wingFeather]

Every lowered 240 I've seen has this characteristic.

[NismoS13Ks]

possibly frame damage. My coupe sits higher on the drivers side due to being hit there.

[nifares240]

preload does affect height. when you add preload, you raise the suspension to prevent the shock bottoming out.

[poshatch]

preload does affect height. when you add preload, you raise the suspension to prevent the shock bottoming out.

?? shock bottoming out???

preloading it yes raises the car..but i dont quite understand your second statement, the shock will bottom out depending on the amount of force added to it, puting it under preload dosnt change the amount of pressure it takes to bottom that spring out...thats always going to be the same...

if you preload the spring to the weight that that corner is going to hold for example. the spring WILL NOT compress anymore once you put it on the ground again because it would take an additional weight above what the spring is preloaded too to compress it further...

at least thats my understanding of spring dynamics and preloading...

P.S. my car is the same way hahaha i would say most are lol

make the spring snug with the top hat but you dont have to add preload too it...if they feel the same and the bottom purch is the same...then its possible your car is tweeked a slight bit, but maybe try it again from scratch and see if its truly even across the board...thats what id start with, if that dosnt do it then lower the one side a little more

[Gabes13]

I was under the impression that preloading does not raise your car, as ride height is adjusted via bottom mount....

[poshatch]

I was under the impression that preloading does not raise your car, as ride height is adjusted via bottom mount....

it does lol think about it

lets take the front cause its easier to imagine

you have no preload on the spring but its touching the top hat, and the bottom purch is snug against the bottom of the spring. the bottom of the spring is not going to move but the strut moves down from the top when load is put on it

now keep the purch in the same spot and preload the coil 1", the spring will compress the same amount since your putting the same amoung of weight on it (the spring dynamics did not change its still the same spring rate, and compresses to the same as before) so when weight is added the spring is the same length but the car is higher because the base of the spring is higher...

that make sense?

here is a visual...



1 is the spring with no preload and no weight on it
2 is the spring when compressed with weight, i just kept the purch all at the same length so that gap is how much its lowered when compressed
3. is when you preload it to the same weight that is going to be put onto it and the more green you see is how much you raised it from the origional possition to get that preload, notice that it is larger than 2, in order to get it to the same height as 2 youd have to raise the yellow the same length as the added green

lol

same reason you cut springs and not compress them to lower the car...same reason that when your maxed out on the purch you droop the spring and not preload it to go lower

[Yasko]

Well my car is at the garage getting inspected, but when I get it back I'll look to see if the frame is bent or something. If not, I guess I'll Just keep lowering the Back right...idk

[poshatch]

Well my car is at the garage getting inspected, but when I get it back I'll look to see if the frame is bent or something. If not, I guess I'll Just keep lowering the Back right...idk

haha bro man im sorry

i hella got side tracked off the OP

but yeah this seems to be an issue with most coilover installs, i have the same problem

i did it perfect, pulled them out, did one the way i wanted it, matched the other one down to to the thread and put them on and one was always lower than the other on my clean titled 240

so just got to do your best and then fix it by whatever means you can, it sounds like you set them up correctly so if you can lower then i say go for it

plus stance GR+ Pro are win

[Gabes13]

I won't lie, I didn't understand anything you said except for the last sentence, which I think is still false. From experience, I have found that pre loading the springs on a coilover that's bottom mount adjustable the car would indeed be lower. It may handle worse, but is by far lower. Either my eyes are playing tricks on me, my tape measurer is wrong, my coilovers are broken, or I'm just dumb.

One thing that we both can agree on is the amount of force it takes to compress the spring and damper doesn't change, as the spring is linear. An 8kg spring will always need 8kg to compress 1mm. So why would compressing a spring via pre load be any different? Static, the damper would compress the same, and even though the spring is shorter from pre load, the spring will compress the same. So, the car would be lowered X mm from pre load and Y mm from static weight. Preloading a spring does essentially the same as using a shorter spring b/c the over all length of the springs from seat to seat is the same. No?

Drooping a spring does the same, but for a different reason. People droop springs (common in the rear coilover) because they have maxed out the adjustability range of the bottom mount. Since you can no longer raise the bottom mount due to the length of the damper, you droop or lower the spring. This essentially puts more weight on the damper shaft, and lowers the car until the spring is seated at the top.

This is what I believe is true with bottom mount adjustable coilovers.

What you're saying, or what I understood, is that preloading a spring X mm will essentially rebound the damper X mm therfore raising the car X mm. That, I don't believe is true when the suspension is static.

[poshatch]

I won't lie, I didn't understand anything you said except for the last sentence, which I think is still false. From experience, I have found that pre loading the springs on a coilover that's bottom mount adjustable the car would indeed be lower. It may handle worse, but is by far lower. Either my eyes are playing tricks on me, my tape measurer is wrong, my coilovers are broken, or I'm just dumb.

One thing that we both can agree on is the amount of force it takes to compress the spring and damper doesn't change, as the spring is linear. An 8kg spring will always need 8kg to compress 1mm. So why would compressing a spring via pre load be any different? Static, the damper would compress the same, and even though the spring is shorter from pre load, the spring will compress the same. So, the car would be lowered X mm from pre load and Y mm from static weight. Preloading a spring does essentially the same as using a shorter spring b/c the over all length of the springs from seat to seat is the same. No?

Drooping a spring does the same, but for a different reason. People droop springs (common in the rear coilover) because they have maxed out the adjustability range of the bottom mount. Since you can no longer raise the bottom mount due to the length of the damper, you droop or lower the spring. This essentially puts more weight on the damper shaft, and lowers the car until the spring is seated at the top.

This is what I believe is true with bottom mount adjustable coilovers.

What you're saying, or what I understood, is that preloading a spring X mm will essentially rebound the damper X mm therfore raising the car X mm. That, I don't believe is true when the suspension is static.

yeah probably a bad explination

and i will probably have to read your post a few times to fully realize the area in which were not quite seeing eye to eye on however from my own experience preloading the rear did raise the car lol so both are experiences are differing so there must be somethign amiss here

lets return to that lame picture i made for the convo

fyi i dont mind being wrong, just want to know why im wrong ya know...

so lets say you got 200kg going on the coilover in that corner of the car

you adding 200kg of preload too it OR no preload and lowering the cars weight on it(200kg) will compress the spring to the same exact length correct? we can agree on this because its a linear spring...yes?

ignoring the bottom purch what is the significant difference in those two set ups in relation to spring height, nothing right? were ignoring where its mounted to the car so as far as the spring is concerned they are exactly the same length

but

if we had the purch in the same spot non preloaded...then added preload, now whats the difference? you will notice that in order to preload it you must raise the bottom spring collar up...thread above the purch that is the green i was talking about and you will notice that if the purch does not move and you move the bottom collar up you will have alot more threads showing above the purch...yes? invision it in your mind.

would this not be EXACTLY the same ride height as running NO preload and lowering the bottom purch down by the same amount of threads that you would see above it if you preloaded it...

because no matter what you do the spring length will ALWAYS be the same length compressed (whether its 200kg of weight or 200kg of preload) and the only changing factor in height is the purch which when you preloaded it was more thread above the purch means its effectivly RAISING the car...does this make sense because i cant explain it better...

they make full length adjustable coilovers so that you can adjust preload and compensate for the change in hight by also raising the purch the same distance you preloaded the spring from the lower spring collar...this is what i understand to be the rational behind the height/preload adjustments being independent of eachother

now if you see a flaw in my rational please correct me so that i may understand the real truth behind the error in my thinking

[Gabes13]

so lets say you got 200kg going on the coilover in that corner of the car

you adding 200kg of preload too it OR no preload and lowering the cars weight on it(200kg) will compress the spring to the same exact length correct? we can agree on this because its a linear spring...yes?

I agree

ignoring the bottom purch what is the significant difference in those two set ups in relation to spring height, nothing right? were ignoring where its mounted to the car so as far as the spring is concerned they are exactly the same length

If the amount of weight loaded on the NON pre loading set is the same as the amount of pre load on the other, I agree, they are the same static (on the ground).

if we had the purch in the same spot non preloaded...then added preload, now whats the difference? you will notice that in order to preload it you must raise the bottom spring collar up...thread above the purch that is the green i was talking about and you will notice that if the purch does not move and you move the bottom collar up you will have alot more threads showing above the purch...yes? invision it in your mind.

If by perch you mean the bottom mount that the knuckles connect to, then yes, I agree more threads will show up when pre loaded (more threads between the bottom spring seat and bottom mount.

would this not be EXACTLY the same ride height as running NO preload and lowering the bottom purch down by the same amount of threads that you would see above it if you preloaded it...

Probably. I'll explain my thoughts down here vvvvv

because no matter what you do the spring length will ALWAYS be the same length compressed (whether its 200kg of weight or 200kg of preload) and the only changing factor in height is the purch which when you preloaded it was more thread above the purch means its effectivly RAISING the car...does this make sense because i cant explain it better...

I think I get it. Since you mentioned the rear suspension, I'll reference it in my theory. I agree that 200kg of load and 200kg of pre load would indeed present the same ride height IF the bottom mount is not touched. That's because the mounting points have not been changed and the loads are the same, ergo presenting the same ride hight. But if you add 100kg of extra preload (300kg) then I would agree the car would appear raised static simply because the rear does not have the extra 100kg to compress the spring. So, a car unloaded (in the air, with the suspension completely rebound, NOT on the ground) a suspension with 300kg of preload and a suspension with 0kg of pre load would be the same because the distance between the top and the bottom mounting points are the same. But static, the 300kg of pre load car would be higher because it has 100kg extra than the actual weight of the car, ergo preventing the suspension from actually compressing the same as a NON pre loaded set. If that's what you're trying to say, than yes, I agree. Pre loading would raise your car, but it has to be more than the actual weight applied. Phew.

What I don't understand is why you wouldn't raise the bottom mount. The bottom mount is what makes the coilover fully adjustable. I you really wanted to get low, preloading the spring would present more thread (which you mentioned earlier), and allowing you to raise the bottom bracket, decreasing the top and bottom mounting points, lowering your car more. That's what I was getting at.

[poshatch]

yessss we came to an understandin and yes for the front thats what te full length allows for the preload compensation by raising the bottom mounting point

the front is never the problem though on our caars

its always the back that seems to have the issue haha

but i think there was one thin that you missed and i might be able to explain it better haha

ok so you know the springs base is where the weight is being supported, where the force of the spring is pushing up against the weight being put on the car the top of the spring compresses down towards that point right...that would be the "base"as it were (the bottom spring collar), when you preload it you raise the base so the spring travels downard till the spring is the same length as before but your base has risen, so this means that even if you add 10kg of preload (lets say on a 10kg/mm spring) you just raised your car 1mm cause to get the preload your raising the base of the spring higher...make sense, it isnt just when the preload matches or is greater than the weight applied put on it i used that as an example to keep it easier to understand..but you get what im saying right

you raised the car that 1 mm so you raise the bottom purch (mount, whatever) up 1mm to compensate for that to get the same right height as before =]

i think this subject got majorly off topic haha but maybe somebody in the future will read and get something out of it because it took me a long long time to figure out all this stuff haha