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Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

Jack up the car again and pull that coilover off the car. Now - leave the bottom perch as is - don't touch it. Pop off the top camber plate, and pull the 8" spring off the shock. Put on a 6" main spring, and a 3" tender spring, and put the top camber plate back on. Put the coilover back onto the car. With the car at full droop in the air, the shock is fully extended and the main spring is fully extended. However - the tender spring should be slightly compressed. (it should be noticeable) Now lower the car back down, and the tender spring will compress 100% all the way to flat as a "block". This is known as "block height". Because the tender spring is fully compressed, it has now gone from roughly 3" in height down to 1" or so. Therefore, your shock is now also compressed by another 2". You've now gained 2" in droop travel, BUT you have reduced your bump (compression) travel length. At static the car looks 100% the same, but the shocks are already compressed and there's now less room before you hit the internal(?) bump stops.
THIS is what I have been thinking but couldn't put it in words. That is assuming the shocks have enough travel (either way) to accomplish something helpful.

Here is another super important thing that I learned: When you are testing droop travel, you really need to jack up the car from the middle. Front skidplate or rear diff. If you jack up from the side, you won't be at true full droop. It will look like you are, but the force from your swaybar on the opposite side of your car is actually holding the shock *UP* in place.
Thanks for sharing Acejam and Yazel. Neither willub (right?) or I even run a rear bar at this point to combat the lifting issue.
 

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Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

Here is another super important thing that I learned: When you are testing droop travel, you really need to jack up the car from the middle. Front skidplate or rear diff. If you jack up from the side, you won't be at true full droop. It will look like you are, but the force from your swaybar on the opposite side of your car is actually holding the shock *UP* in place.
Very true!

But for my own personal test, was I thinking correctly to jack up one corner at a time (just enough to go full droop without removing any weight from the other three wheels as much as possible) with the bar connected, measuring, and then disconnecting the bar completely on both sides and re-measuring to measure if I was fully drooping with and without the bar (in a simulated corner kinda...)?

I think I was at least measuring something useful. After measuring droop at one corner with the bar on its stiffest setting, you could measure more and more droop as you lowered the stiffness settings on the bar (on both sides) and a lot more droop with the bar completely disconnected on both sides. After adding tender springs and checking that they fully compressed under the weight of the car at a static ride height, I put my rear bar setting to the middle setting after doing my test again as I was achieving the same droop with the bar completely disconnected as I was with it in the middle setting combined with the tenders! I thought/think I had a breakthrough in that moment :lol:
 

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Discussion Starter #983
Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

Thanks for all the info guys. Now all of this stuff is hammered into my brain :lol:

Out back on my car I actually use a tender spring with something like 6k of spring rate. I use this not only to bridge the gap between the main spring and the spring seats, but also to force the damper down while it is drooping to help reduce inside wheel lift/counteract the rear sway holding the damper up. Luckily this spring rate does not add to the effective spring rate from my main spring as it is fully compressed with the weight of the car.. it only takes effect as the shock starts to droop/uncompress.
.
IMO, this is what you want Matt if you still have rear inside lift issues next season. (and correct, no rear bar for me still)
 

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Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

What Acejam just said was the test i was referring to. You need to make sure you don't compress the strut too much. Sacrificing bump travel for droop travel takes some solid tests so you don't break something.

I'm not sure how much bump travel the FAs have but with 700lb springs they aren't compressing much.

Without a rear sway bar I'm surprised you're running a standard weight split of 100lbs/in (2kg/mm).

Even with my sways I prefer a 1kg/mm or 50lbs/in difference front to rear.

With no rear sway I'd wager it's worth testing stiffer rear rates to offset the lost roll resistance.

I need to build a new suspension setup with some stiffer rates so I can tinker next year.

It maybe worth it to get them revalved so you're not at the top of the adjustment range.
 

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Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

Thanks for all the info guys. Now all of this stuff is hammered into my brain :lol:



IMO, this is what you want Matt if you still have rear inside lift issues next season.
And then start looking at front end bar/spring stiffness if not all over spring stiffness (including the rear with the lack of any swaybar) if it continues to lift (I think :lol:)

I edited my last post with more info.. hopefully someone can confirm I was thinking correctly.
 

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Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

Very true!

But for my own personal test, was I thinking correctly to jack up one corner at a time (just enough to go full droop without removing any weight from the other three wheels as much as possible) with the bar connected, measuring, and then disconnecting the bar completely on both sides and re-measuring to measure if I was fully drooping with and without the bar?
I think this could work too - but I've never tried it before. If you don't have a rear sway (or disconnect it) then it gets rid of the tension on the shock - which should allow full droop.

Here's another thing to think about: When you are on course and cornering hard, that inside rear wheel might not be at full droop due to your swaybar holding it up. Removing the rear bar helps this dramatically. But if you were to go off a jump with the car, both wheels on the same axle would droop at the same time - making the sway bar a non-issue.
 

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Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

I never really thought about it in terms of these guys having no sway bar at all back there.. so I guess my test would be useless for them! Your test is the only way they could really test things out!

And yea basically thats what I found with my test (with a bar). After the addition of the tender springs, I could get the same droop measurement with the bar completely disconnected as I could with the bar in its middle setting. SO I assume this means it was drooping as far as the dampers physically could anywhere from the middle swaybar setting on down. And just to back this up, I put the bar on its stiffest setting and I lost droop travel versus the bar disconnected.
 

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Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

I did end up solving it for the most part I believe. A lot less bucking/diff binding and a lot less reports from people I had watching the car on course about inside wheel lift (photos backed up). I think it could still be better though.

I have a lot of ninja edits in all of my previous posts above. You guys have me thinking so much :lol:
 

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Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

I'm thinking, in my case, that simply upping the rates (especially the front) will help reduce some lift anyways since I shouldn't be overpowering the springs any more.
 

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Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

I'm thinking, in my case, that simply upping the rates (especially the front) will help reduce some lift anyways since I shouldn't be overpowering the springs any more.
I think this will help greatly. Ever sat at a table when one of the legs is too short? (undersprung) The opposite corner lifts!
 

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Discussion Starter #992 (Edited)
Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

What Acejam just said was the test i was referring to. You need to make sure you don't compress the strut too much. Sacrificing bump travel for droop travel takes some solid tests so you don't break something.

I'm not sure how much bump travel the FAs have but with 700lb springs they aren't compressing much.

Without a rear sway bar I'm surprised you're running a standard weight split of 100lbs/in (2kg/mm).

Even with my sways I prefer a 1kg/mm or 50lbs/in difference front to rear.

With no rear sway I'd wager it's worth testing stiffer rear rates to offset the lost roll resistance.

I need to build a new suspension setup with some stiffer rates so I can tinker next year.

It maybe worth it to get them revalved so you're not at the top of the adjustment range.
They don't have much bump travel, that's for sure.

I haven't been driving the car long enough to really say what I prefer. I felt like this past season was the first time I was actually "driving" the car, if you know what I mean. All I know is that with the 24mm rear sway on its softest setting, the car was awful. Super twitchy and lifted the inside rear tire around every corner really. Disconnecting it fixed all of that, but the car does tend to plow rather than rotate. I'll be trying different things next season. I still have the stock sway bars kickin around.

I'd revalve them if I had the money. If they end up being really bouncy or something with the new springs it may come down to that.


And then start looking at front end bar/spring stiffness if not all over spring stiffness (including the rear with the lack of any swaybar) if it continues to lift (I think :lol:).
Yep. I don't think increasing rear spring rate will help with the lifting issue though, especially without assist springs. The stiffer the spring, the less the shock compresses with the car's weight, which means you have even less droop travel available for when it tries to lift. I think this is part of mickles problem since he has more spring out back. Maybe more spring would help with a sway bar though, since the spring will be fighting against the bar more. I don't know :lol: I guess that's what all the tests you guys suggested are for :)

I'm thinking, in my case, that simply upping the rates (especially the front) will help reduce some lift anyways since I shouldn't be overpowering the springs any more.
Definitely. Next season should be interesting!
 

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Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

Yep. I don't think increasing rear spring rate will help with the lifting issue though, especially without assist springs. The stiffer the spring, the less the shock compresses with the car's weight, which means you have even less droop travel available for when it tries to lift. I think this is part of mickles problem since he has more spring out back. Maybe more spring would help with a sway bar though, since the spring will be fighting against the bar more. I don't know :lol: I guess that's what all the tests you guys suggested are for :)
Increasing rear main spring rate won't help with the lifting issue out back, you are right. But what I was getting at and something I have experienced is actually lifting the inside front tire without enough rear spring (and by this I mean I removed my rear swaybar all together just to test).. so that is something to factor in too and make sure isn't occuring. The main spring rate increase will never help with increasing droop, but a tender will in some cases. Increasing main spring rate won't sacrifice droop without a sway counteracting the damper either, but it can reduce bump travel overall if it is just overly stiff and overpowering the damper I would think.

We'll all figure it out at some point... until then we have Ace's notes to save us! :lol:
 

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Discussion Starter #994 (Edited)
Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

Oh ok, gotcha on the front lifting. Don't want none of that, this ain't no bimmer forum!

Increasing main spring rate won't sacrifice droop without a sway counteracting the damper either
It won't? Here's my thinking. Let me know if it's wrong :lol:

Say the rear suspension is supporting 1000 pounds of the car. You have a spring on each side with a rate of 250 lb/in. So each spring is supporting 500lbs., and the rear suspension of the car will compress 2 inches and give you 2 inches of available rebound. Double those spring rates to 500 lb/in on the same car and the rear suspension only compresses 1 inch, cutting your available rebound in half. It's an exaggerated example to explain my thinking, but yeah.
 

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Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

We are on the same page, but I am calling bump travel what you are calling droop I think haha!

If that makes sense.. Yea there will be a difference in how much the damper can compress depending on the main spring rate, but how much it can uncompress (droop) should be the same without a swaybar counteracting the damper as long as you don't have a droop limiting system installed.
 

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Discussion Starter #996
Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

Yea there will be a difference in how much the damper can compress depending on the main spring rate, but how much it can uncompress (droop) should be the same without a swaybar counteracting the damper as long as you don't have a droop limiting system installed.
When you say "same", what are you referring to? That droop will be the same as how much the damper compresses with the car's static weight on it? I'm leaving sway bars out of my explanation up above. All I'm saying is that how much the damper compresses when the car is on the ground, not moving, is how much droop you will have. Increasing spring rate reduces static compression, which reduces droop. I'm probably just misunderstanding you :lol:
 

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Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

I see what you are getting at for sure and I only mentioned a sway bar because it is something that can limit droop and I wanted to clearly state that that it wasn't a part of my explanation, but I didn't do that so well :lol: In my explanation I want there to be no helpers, no tenders, no bars, or droop limiting systems so it's just a raw main spring and damper. And in my explanation I assume the damper is working correctly and can effectively droop on its own.

But again, the main spring is only there to hold the car up, it has no effect the amount of droop (the amount of uncompressing the damper can achieve). Regardless of how much that spring let's the damper compress with the car on the ground not moving the droop will be the same with any given main spring (or any other spring that always has an effective spring rate i.e. Not helpers or tenders). You could have a really stiff spring that doesn't allow the damper to compress at all and it will still droop the same amount when unloaded as it would with a really light spring that compresses with the weight of the car on it. The ride height difference with the car on the ground would be the only thing you would notice. At least that is how it works in my brain, I most definitely could be wrong :lol:
 

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Discussion Starter #998
Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

I see what you are getting at for sure and I only mentioned a sway bar because it is something that can limit droop and I wanted to clearly state that that it wasn't a part of my explanation, but I didn't do that so well :lol: In my explanation I want there to be no helpers, no tenders, no bars, or droop limiting systems so it's just a raw main spring and damper. And in my explanation I assume the damper is working correctly and can effectively droop on its own.

But again, the main spring is only there to hold the car up, it has no effect the amount of droop (the amount of uncompressing the damper can achieve). Regardless of how much that spring let's the damper compress with the car on the ground not moving the droop will be the same with any given main spring (or any other spring that always has an effective spring rate i.e. Not helpers or tenders). You could have a really stiff spring that doesn't allow the damper to compress at all and it will still droop the same amount when unloaded as it would with a really light spring that compresses with the weight of the car on it. The ride height difference with the car on the ground would be the only thing you would notice. At least that is how it works in my brain, I most definitely could be wrong :lol:
The damper can not physically extend any further though. The last picture I posted with my coilovers is a good example. They are all extended to the max in the picture. If I put a 5000# spring on them, they wouldn't compress at all with the car's weight, which means they can't droop at all when you lift the car up. The damper has to compress to allow rebound.
 

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Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

If the damper is not compressing at all, that just means it is being forced to be at full droop all of the time in my head. Even with a 5000lb spring it would depend on the amount of preload and spring length to determine if the damper compressed at all, not only the spring itself. It could still compress some if the 5000lb spring had no preload and the damper compressed under the weight of the car until it finally fell to the spring. If a spring was so long and so stiff with enough preload that the damper could not compress at all, it would simply be at the dampers full droop all the time. So in that way, yes the damper cannot droop anymore due to the spring, but it isn't limiting droop because it won't let the damper compress it is forcing the damper to be at max droop all of the time. So in the case of you guys with independet ride height and preload settings combined with a damper that has minimal droop travel in the first place I see what you are getting at.

So yes, by having a spring that compresses under the weight of the car which also allows the damper to compress some, you do allow the damper to uncompress and droop when it is unloaded. But at full droop in that situation the damper would still be extended to the same length as it would be if you had a spring that didn't allow it to compress at all in the first place (i.e. Forcing the damper to be at full droop the whole time). So I suppose yea, it can't droop in that situation, but only because it is being forced to be at full droop all of them time. Again it isn't actually limiting droop travel in my brain, it is limiting bump travel (compression) while being forced to be so uncompressed in the first place that it is already fully drooped/extended.

We are getting at the same thing, but thinking of it in different ways :lol: Basically we said the same thing and my brain thought of it in a different manner than yours, so I typed out a bunch of repetitive crap that you already knew to just agree with you in a roundabout way. :lol:
 

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Discussion Starter #1,000
Re: Willub's 04ish 1.5XTR SM STi: New Daily Driver!

Ok, I get what you're saying now. LOL. Finally. Well, we beat the shit out of that topic! :lol:

Moving on!
 
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