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Asphalt Surfers Unlimited
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758 Posts
Discussion Starter #1
There is a lot of speculation that floats around about Impreza struts and Forester struts and mixing and matching and what works and what doesn't.

I got the hard data from KYB directly, they manufacture the OEM struts themselves in all the variations, and they produce the most common OE replacement and OE fitment sport shocks currently available for the Subaru platform.

All measurements are in Millimeters.

The Differences:
Code:
FRONT
  Lower Hole To Spring Seat
     Impreza   252
     Forester  253
  Total Strut Body Length
      Impreza   356
      Forester  377
  Extended Length (Body + Shaft)
       Impreza   525
       Forester  560 [514]
  Compressed Length (Body + Shaft)
       Forester  391

REAR
  Lower Hole To Spring Seat
     Impreza   315
     Forester  330
  Total Strut Body Length
      Impreza   367
      Forester  407
  Extended Length (Body + Shaft)
       Impreza   605
       Forester  643 [632]
  Compressed Length (Body + Shaft)
       Forester  455
Hopefully this will help some of you with the differences in strut geometry.

The second figure on the Forester extended length measurements is due to the internal droop limiting spring that is in the Forester struts. The figure in brackets is the free extension before the spring becomes involved. The total extension is the length when the limiting spring is fully compressed (shaft fully extended under load).

I have not touched on the differences in spring length or preload, those are equally important figures... but this chart should illustrate why there are different spring designs between the Impreza and Forester.


Enjoy,

Porter
 

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Developer
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142 Posts
Did you by chance get the difference in total stroke w/o the spring (fully compressed to fully extended)? That would be tremendously helpful. I am working on trying to make some sort of adapter to fit the AGX shocks/struts onto Foresters.
 

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Asphalt Surfers Unlimited
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758 Posts
Discussion Starter #5
I believe both struts retract almost fully into the housing, with about an inch of shaft exposed. The "fully extended" measurement is to the top of the chrome shaft surface, not including the threaded area.

Subtracting the strut body length from the total extended measurement should give you a rough idea of the length of total travel.

I will call KYB back tomorrow and get a real answer on the total stroke.

BTW... I don't think it's going to be easy to "adapt" AGXs to the Forester and keep Forester geometry... the spring perch height and total travel are quite different.

My personal solution would be to use a set of Koni inserts sized for the Forester, or a Forester-specific coilover.
 

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The Modfather
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8,098 Posts
Just a little pic to add since I happen to have one, notice the top of the Foresters strut, it appears the top can be screwed off but I have not tired myself. I'm not sure if it's threaded or not.
 

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Asphalt Surfers Unlimited
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758 Posts
Discussion Starter #7
Peaty,

It's not threaded. That is a standard KYB/Showa strut top cap. It is press-fit into place and holds the inner strut cartridge assembly in place. There is a seal system underneath the cap.
 

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Asphalt Surfers Unlimited
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758 Posts
Discussion Starter #9
Peaty said:
Is there a way to remove the cap, change the insert and put a new cap on?
If you remove the cap the strut is essentially "ruined" for KYB-valving purposes. :icon_wink:

It is however quite ideal for Koni-insert use... though the housing will need to be trimmed down somewhat (slightly) depending on the exact length of the Koni insert.

Hmm... lots of Koni interest here. I'll be on the phone with Koni tomorrow. :biggrin:
 

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Asphalt Surfers Unlimited
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758 Posts
Discussion Starter #10
EDIT

Added compressed length to the figures. Note that this is total body and strut shaft to the end of the chrome rod area, not including the threaded end.
 

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Asphalt Surfers Unlimited
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758 Posts
Discussion Starter #12
I have not gotten a chance to speak with the folks at Koni, work has been crazy. I know the right individual there though, we worked together somewhat on the SVX fitment inserts a few years ago.
 

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Registered
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5 Posts
Koni inserts

Anywork from koni?
Can we usethe Koni incerts?
..........Don't know if this will help,but you can try contacting Dave or Barrett at www.allwheelsdriven.com, he might be able to help you out or at least answer your questions.They have been been fabbing up Subaru strut bodies to take Bilstein HD strut inserts(same as Koni I believe) for Impreza rally cars,they have the screw top which you need anyway,H&R springs,Group N top hats
 

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Asphalt Surfers Unlimited
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758 Posts
Discussion Starter #16
..........Don't know if this will help,but you can try contacting Dave or Barrett at www.allwheelsdriven.com, he might be able to help you out or at least answer your questions.They have been been fabbing up Subaru strut bodies to take Bilstein HD strut inserts(same as Koni I believe) for Impreza rally cars,they have the screw top which you need anyway,H&R springs,Group N top hats
It's www.allwheelsdriven.net I believe.
 

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Premium Member
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380 Posts
You can use the Koni inserts for the WRX. Total strut travel is reduced but it will work perfectly on a lowered car.
Could someone help me out with some part numbers for the Koni inserts for the WRX? I have the Whiteline Control springs and I am getting sick of the bouncy ride. Ohh what I wouldn't do for some Bilsteins.

Thanks,
 

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Premium Member
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380 Posts
Koni's - 8610-1351 front, 8610-1440 rear
THANKS!!! I will call my local install shop to get a quote. I hadn't been following this board for a few weeks so I wasn't aware of this option. I am really tired of the bouncy ride and from the few folks I've talked to they were less than impessed with the KYB GR-2's. (My previous car had H&R Sport springs with Bilstein shocks....ohh so nice)

Thanks,
 
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