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Old 10-26-2008, 03:52 PM   #1
sexycat
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Default KYB GR2 or KYB AGX?

whats the different between them?
totally different price.

i like off roading, and also looking for daily driving comfortably.

which one is best choice for me ?
so i need stiffer struts or softer?
thanks
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Old 10-26-2008, 05:12 PM   #2
SubeN'Siren
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Well...many people end up setting the agx's to about wht the GR2's are.
Is there a difference in the warranty?
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Old 10-26-2008, 05:29 PM   #3
akryder86
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Go with the AGX's as they have adjustable damping. You'll be able to set the suspension up the way you want it. The GR2's are essentially just a stock replacement shock. I have the AGX's with a Ground Control coilover kit with 340#/in. springs and absolutly love the setup for the street. For gravel roads I'm getting a set of the Tein Gravel springs to put on the AGX's.
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Old 10-26-2008, 08:06 PM   #4
supersuby2
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AGX for sure..... you will want the added damping if you start pushing your car off road to help keep it from bottoming out...
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Old 10-27-2008, 12:48 AM   #5
williaty
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You asked this exact question somewhere else and I've answered you there. Can't remember for the life of me where...
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Old 10-27-2008, 01:50 PM   #6
Back Road Runner
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GR2 = non-adjustable

AGX = adjustable

AGX Impreza RS version - 4-way front, 8-way rear adjustment, dampening rates based off 02 Impreza sedan as the "base" damper rates

AGX WRX version - 4-way front, 4-way rear adjustments, dampening rates based off 03 WRX Impreza sedan as the "base" damper rates

Small note, KYB who makes the GR2 and AGX also make the stock oem dampers for Subaru, i.e. the stock dampers on your car right now are KYB made. They simply mimic the stock profiles and bump it up some.

Here's a comparison of the AGX to the stock WRX, Koni, and D-Spec struts in rates and range. Note that the AGX shown is the front only. The rear is a little lower. The D-Spec and Koni are the same front and rear. The AGX is based off the WRX, so it does vary as the WRX varies front and rear. I'm just showing the front rates here. These are shown at one speed, 0.3 m/sec. The profiles actually vary by speed. This is simply one commonly measured point. The D-Spec is linear, the Stock WRX and I assume AGX are slightly digressive, and the Koni is a little heavy in the low speed and mild at higher speeds.


D-Spec:


Koni (at full stiff) and Stock WRX (front):


I've never seen specific plots for the AGX struts, but they are modeled after the oem struts that are also made by KYB. I would assume a similar profile.

Note, the Koni compression(bump) dampening is fixed and does not change from firm to hard. Only the rebound changes. The AGX and D-Spec are set via a ratio between compression and dampening, generally in the range of 1:2 to 1:2.5. This ratio remains relatively constant as you change from soft to firm. There are certain advantages/disadvantages to each approach. Note that the D-Spec ratio is closer to 1:2 and the AGX ratio a little higher towards 1:2.5. The D-Spec offers a little firmer compression relative to rebound then the AGX. This provides a touch more control/firmness for the same rebound setting relative to the AGX.

I'll also note that the stock setting, when paired to the stock 163 lb/in spring rate is 40% compression and 90%-100% rebound dampened in the front. With stiffer aftermarket springs, you can approach this same ratio for a similar to stock type of ride behavior. You don't want to go over 100% for rebound but at the same time you want enough compression dampening for good bump control and to prevent bottoming. Rates need to be high enough to work effectively but not too high to constrain free movement and make the suspension too firm and/or sluggish in response. Too light, and the chassis can bound over bumps and be kind of sloppy and uncontrolled. You want the happy medium. You can also see why the slightly lower compression:rebound ratio of the D-Spec is favorable and that the Koni fixed compression may be favorable/unfavorable depending on the spring rates you choose. "Ideal" dampening is considered to be around 60%-70%. Stock sort of averages out to this in the combined motion, but the compression is set lower for comfort over bumps, sacrificing some control for this comfort.
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Old 10-27-2008, 10:33 PM   #7
sexycat
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Quote:
Originally Posted by williaty View Post
You asked this exact question somewhere else and I've answered you there. Can't remember for the life of me where...
i belive its on dirtyimpreza.com
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Old 10-27-2008, 10:39 PM   #8
sexycat
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Quote:
Originally Posted by Back Road Runner View Post
GR2 = non-adjustable

AGX = adjustable

AGX Impreza RS version - 4-way front, 8-way rear adjustment, dampening rates based off 02 Impreza sedan as the "base" damper rates

AGX WRX version - 4-way front, 4-way rear adjustments, dampening rates based off 03 WRX Impreza sedan as the "base" damper rates

Small note, KYB who makes the GR2 and AGX also make the stock oem dampers for Subaru, i.e. the stock dampers on your car right now are KYB made. They simply mimic the stock profiles and bump it up some.

Here's a comparison of the AGX to the stock WRX, Koni, and D-Spec struts in rates and range. Note that the AGX shown is the front only. The rear is a little lower. The D-Spec and Koni are the same front and rear. The AGX is based off the WRX, so it does vary as the WRX varies front and rear. I'm just showing the front rates here. These are shown at one speed, 0.3 m/sec. The profiles actually vary by speed. This is simply one commonly measured point. The D-Spec is linear, the Stock WRX and I assume AGX are slightly digressive, and the Koni is a little heavy in the low speed and mild at higher speeds.


D-Spec:


Koni (at full stiff) and Stock WRX (front):


I've never seen specific plots for the AGX struts, but they are modeled after the oem struts that are also made by KYB. I would assume a similar profile.

Note, the Koni compression(bump) dampening is fixed and does not change from firm to hard. Only the rebound changes. The AGX and D-Spec are set via a ratio between compression and dampening, generally in the range of 1:2 to 1:2.5. This ratio remains relatively constant as you change from soft to firm. There are certain advantages/disadvantages to each approach. Note that the D-Spec ratio is closer to 1:2 and the AGX ratio a little higher towards 1:2.5. The D-Spec offers a little firmer compression relative to rebound then the AGX. This provides a touch more control/firmness for the same rebound setting relative to the AGX.

I'll also note that the stock setting, when paired to the stock 163 lb/in spring rate is 40% compression and 90%-100% rebound dampened in the front. With stiffer aftermarket springs, you can approach this same ratio for a similar to stock type of ride behavior. You don't want to go over 100% for rebound but at the same time you want enough compression dampening for good bump control and to prevent bottoming. Rates need to be high enough to work effectively but not too high to constrain free movement and make the suspension too firm and/or sluggish in response. Too light, and the chassis can bound over bumps and be kind of sloppy and uncontrolled. You want the happy medium. You can also see why the slightly lower compression:rebound ratio of the D-Spec is favorable and that the Koni fixed compression may be favorable/unfavorable depending on the spring rates you choose. "Ideal" dampening is considered to be around 60%-70%. Stock sort of averages out to this in the combined motion, but the compression is set lower for comfort over bumps, sacrificing some control for this comfort.
thank you very much for the helpful information,but it seems to me a little difficult to understand. haha
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Old 10-27-2008, 11:12 PM   #9
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Take some time to learn about basic car physics, the spring/damper/mass behavior, what under, critical, and over dampened means. You will be confused for a while until you start piecing the concepts together and getting a better picture. All I want from you now is to think a little and to start learning about these things. This will help you understand what's going on and to better adjust your setup.

Keep in mind that spring rates can be linear or non-linear (progressive).

Keep in mind that damper rates are a resistive force relative to the speed of motion. An example would be a hand operated bike air pump. Most folks have probably used one. If you pump slowly versus a medium speed, versus quickly, the resistive force against you varies. The air is shoved through valving between the pump and tire, and there is some valving/leakage of the piston that moves up and down within the pump. Depending on speed, it will create a specific resistive force to motion. Car dampers do the same thing and resist the motion of the spring. This dampens the spring movement and controls the movement of the mass in oscillation.

Controlled movement is the key.

Damper rates also can be linear or non-linear as well.

There are different goals to the linear and non-linear behaviors.

For non-linear springs, the goal is to have a soft initial range that makes for a more comfortable ride over small bumps but at the same time provide a stiffer range beyond that for performance use and body roll control. Linear is easier to work with and does not change through the range of compression. One could say it's more precise for sport/race use.

For non-linear dampers, it can vary in many ways. Generally a bump in low speed dampening helps control chassis movement and mild high speed dampening helps maintain a comfortable ride over bumps. It is less linear though and varies depending on the movement speed. Linearity is easier to control for sport/race use, but does not take advantage of some aspects that improve comfort/behavior that a person may want.

From a scientific standpoint, we would like to see 100% compression and 100% rebound dampening for a specific spring rate and chassis mass. In reality this is never done, and dampening rates vary from low compression/high rebound to high rebound/low compression all depending on what you're doing with the car and how you want the car to behave. For example, a setup for rally cars will be very different from our daily consumer car. We want comfort, they want to take a 10 foot jump and not break the car, completely different requirements. The ideal range has generally been considered to be around 65% to 70% critically dampened. As well, with our consumer oriented low compression/high rebound designs, we aim for the rebound to be somewhere between 70% and 100% and let the compression to be relatively low around 30% to 40% which aids comfort. This is common at the consumer level and can be seen in all the aftermarket damper designs, although, they do vary a little bit.
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Old 12-11-2008, 11:18 AM   #10
jpbiker
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Very interesting topic, I'm beginning to understand more of this stuff now ...

When you're talking about % though what do they refer to ?
I understand the ideal scientific 100% but how do they relate to the graphs ?

And basically on a given spring rate the AGX frt. in the fist graph will be more compliant (compression stroke) on softer settings than the D-spec at the same lower setting, but with more rebound damping ?

How does this relates in real world, what kind of bumps and speed can be associated with .3m/s shaft speeds ?

Basically which of the two will be more compliant/comfortable over real life DD judging from those graphs based on say a fictionnal 215 lb/pds linear spring rate ?

Anybody happens to also have graphs for the AGX ?

Thanks
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