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All I did was make sure both rears were the same length and both fronts were the same length. I am lucky to live 3 miles from a shop that specializes in building drift cars. I am going to have them do the alignment according to the Solstice book specs and double check my install and height measurements
 

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Uggh
Spent 6hrs shoveling dirt and moving a stone wall today.
The way I feel right now, I think I am going to pass on doing my suspension tomorrow.
This type of work takes a toll on a Cyborg with 2 fake hips.
 

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I am interested too.
I am thinking of getting BC's.
Thinking 6K front and 7K rear.
Are y'all going with pillowballs?
Mine is my DD, and may never see a track.
Wonder--can you change between rubber and pillowballs simply? and would it require realignment?
 

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Definitely need an alignment as even if you don't re-adjust them they will lower the car slightly.

I have just the standard BCs and love them. I drive my car just about every day with 7K on all four corners. If I had it to do over again I might consider putting 6ks up front but I like how the car handles now. Doesn't seem to want to push at all unless I go into a corner on autocross WAY too hot.
 

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Decisions, decisions.
I have the z0k sways f & r.
Thinking since I have that on the front,
Stepping the springs down a step from the rear would keep it closer to neutral.

My alignment question wasn't very clear:
If I put these coilovers on with with pillowball option (and aligned) and decide its too rough, and want to switch to the rubber bushings, can this change be made without disturbing the alignment?

Also, which mounts did y'all use?
 

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I doubt you'd be able to tell which mounts you had on there by feel, and while I would expect a change not to affect alignment, I'd still check it afterward.
 

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that thud can be 2 things
1. Bad shock and you are bottoming out
2. the whole shock/coil assembly is not bolted down all the way

The second is not uncommon on our cars after time. The nuts on the top bolts can back out a bit. I would first suggest that you going around and verify all of the nuts are torqued down to the correct spec.
if the sound continues after that, you most likely need to replace a shock.

I will be installing my BC Coilovers this weekend. My shocks are super bouncy right now. I think the amount of time it sat without being driven caused this.

Ahnuld
If I remember correctly you are not too far from me. I have swapped out suspensions so many times on our kappa's that I am pretty quick and efficient. If you get some replacement parts and want help, feel free to drive over to my place. I have the tools and space
Posts like this... make up for so much of the ass-hat-ery in life. I mean yeah, we all offer help and advice... However, not too many people invite folks to their homes to help. :thumbs: :D Thanks Elff :cheers:
 

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Robo, what sways do you have on?
If targeting neutral with even height adjustment (I don't want to lower it [though I could live with maybe an inch], due to speed bumps with which I have to contend), I would preserve the stock roll axis. But I know AXers typically only swap the rear sway to promote oversteer. In some old thread, a racer indicated for solo or street they would put stiffer sway on the front as well (to keep it neutral or slightly under steer-biased).
I have both z0k sways. But the GM springs are all stiffer in the rear. Since I can't afford to buy a bunch of spring options, I am thinking of going 1kg/mm softer up front to start with and putting the fe3 back in up front if 1kg/mm difference not to my liking. Before I invest, I wonder if this is a good plan. (Btw, so far this is only a street car, so despite my desire for neutral handling, I can't do much "testing"), and slight under steer is probably smarter, even though I don't like it.
 

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Ahnuld, hope you will be able to get it back to want you used to have--or even better. I think you will.

Hope you don't mind me using your thread (probably should've started a new one).
 

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It's what it is all about...play it forward. This is why I'm big on doing mod days if you have enough cars in the area. We've had two out here so far and I think it may be time to do another.

Robo, what sways do you have on?
If targeting neutral with even height adjustment (I don't want to lower it [though I could live with maybe an inch], due to speed bumps with which I have to contend), I would preserve the stock roll axis.
First the easy part, I have Redline/GXP Z0K bars front and rear. I've heard the same thing about going with the stock sway bar up front but last time I took the car out it felt balanced. We'll see what I get this time with the new tires.

Now the tricky stuff. I've been SO tempted to play with adjusting our roll center. Considering how our suspension is designed, I keep wanting to put a couple thick washers under the upper outside control arm mounting points and seeing what that does for roll. I don't know if the SCCA guys played with it at all back in the day but every time I look at our suspension I just can't help but think "Giant RC Car".





Roll Center:


I keep thinking if I were to Shorten the upper part of the knuckle I could lower the roll center then use washers to bring it back up.

Not sure how SAFE that would be BUT...lol

Now if you put shims on the bottom link, that could raise your roll center some and give you less of a roll moment after lowering.

But I know AXers typically only swap the rear sway to promote oversteer. In some old thread, a racer indicated for solo or street they would put stiffer sway on the front as well (to keep it neutral or slightly under steer-biased).
I have both z0k sways. But the GM springs are all stiffer in the rear. Since I can't afford to buy a bunch of spring options, I am thinking of going 1kg/mm softer up front to start with and putting the fe3 back in up front if 1kg/mm difference not to my liking. Before I invest, I wonder if this is a good plan. (Btw, so far this is only a street car, so despite my desire for neutral handling, I can't do much "testing"), and slight under steer is probably smarter, even though I don't like it.
I feel my car is pretty balanced with the 7Ks all around but we'll see how they work at Autocross. I want to take a FE3 front bar with me and swap it out during the day and see if it helps more. Last time at the track though the car was tail happy. May be completely different with good rubber on it.
 

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Hmmm. I would think shortening the knuckle on top would raise the roll center. (?)

Interesting, but I would think the simplest way to manipulate the roll and CG axes is probably to raise and lower the height with the springs (knowing yours are adjustable).
If the purpose is changing the understeer/oversteer tendencies, I would think changing the height would be fine-tuning compared to sways and spring rates (at least on this car).

And, yes--I have TC, and rarely turn it off.
Still, lay on the gas and she's entertaining!
 

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Hmmm. I would think shortening the knuckle on top would raise the roll center. (?)
If you look at this image:


Your roll center are where the two green lines intersect.

To "calculate" roll center, you draw a line from the outside mounting point of the upper arm to the inside mount of the upper arm and continue that line out indefinitely. You then do the same thing with the lower arm. These are the blue (suspension arms) and red (the line of those two points continuing indefinitely) seen in the above picture. You then make a line from the center line of the tire to the point where the two lines for that tire's suspension arm lines intersect. These are the green lines above.

When you lower the outside suspension arm mounting point you can see how that line moves in relation to the line from the lower arm. This moves the point where they cross further away from the opposite side of the car. This reduces the angle of the green line in relation to the ground. Since that line is moving "down" in relation to the Center of Gravity (CG) the spot where the two green lines intersect will also move down.

When you compress your suspension, you also lower your roll center as you lower your CG. Problem is you usually lower your roll center more than your CG and thus lengthen your roll moment.

Your roll moment is the distance between your CG and your Roll Center. Think of it like an upside down pendulum. The longer the roll moment, the more your car rolls around it's roll center. If you want to reduce roll, you want to shorten your roll moment by bringing the CG of your car closer to the Roll Center. This is where getting rid of weight up high on the car (carbon fiber hoods, fenders, trunks, etc) not only reduces weight but also lowers the car's GG as less weight is carried up high.

By just adding spacers under our outside upper links, we would raise the roll center and shorten the roll moment. With the heavier bars, lengthening the roll moment may compensate for the reduced roll of the bar. However, since the car is lowered and that usually lowers the roll moment more than the amount it lowers the CG, having the stiffer bar may compensate for the longer roll moment caused by lowering without messing with the suspension arm mounting locations.

I don't know the exact schematics of our suspension (though it is one thing that I want to calculate) these are the general principles when it comes to roll center. The fact that our cars have a suspension design that even allows us to ponder this adjustment possibility is pretty special.

Interesting, but I would think the simplest way to manipulate the roll and CG axes is probably to raise and lower the height with the springs (knowing yours are adjustable).
If the purpose is changing the understeer/oversteer tendencies, I would think changing the height would be fine-tuning compared to sways and spring rates (at least on this car).
In general your front end should sit no lower than .5" when compared to what the rear sits at. Thus front to rear ride height should go up and down together and thus the car's balance would be unchanged front to rear. You can dial in a bit more steering by having the front slightly lower than the rear and a little less by having them equal. Generally you don't set your front ride height higher than the rear. So yes, it is a fine tuning adjustment but we're talking very fine. Super fine. Most folks wouldn't notice a difference.

The main point of having the front lower than the rear though has to do with weight transfer on and off power. When off power, more weight will transfer to a slightly lower front end than a front end that sits level with the rear (when static). When power is applied, more weight stays up front increasing on power steering because it doesn't lift as much as it would had it been set to level with the rear suspension. Ride height front to rear is more a fine tuning adjustment of on power steering than it is roll moment front to rear.

That being said, on and off power moments affect the roll moment in comparing front roll moment to rear roll moment. The more the front drops in relation to how much the rear rises changes how much larger the front roll moment becomes off power and how much shorter it becomes on power when compared to how much shorter the rear roll moment becomes off power and how much longer it gets on power. (remember, the roll moment generally lengthens as suspension is compressed and shortens as suspension is extended).

Shock adjustment (softer and firmer settings on your dampers) would be equally fine adjustments and much easier to make. I've dialed steering in and out at the track using nothing more than air pressure and shock adjustments. Sway bars and springs will be greater adjustments. Tires would be the largest adjustment you can make suspension wise by far and every other adjustment our suspension has is minor by comparison.

I don't know how much you already knew about all this stuff but I can't remember a time when roll center was discussed on a full size car forum. We talk about this a lot in the RC world since our on road RC cars have all these adjustments (as well as being able to adjust the length of the suspension arms which also changes roll characteristics). I just want to share this information so others who may not know this kind of stuff can follow the conversation as well. There is a lot more to it than this but this is the basics.

I did some research and they make adjustable ball joints just for this purpose on race cars...Hmmm...I did find this cool little app that lets you see how roll center changes with chassis movement.

http://www.racingaspirations.com/apps/suspension-geometry-calculator
 
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