Author Topic: Koni Strut Insert Install  (Read 2249 times)

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Offline theostubbs

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Koni Strut Insert Install
« on: January 14, 2008, 07:01:48 pm »
Quote from: Theostubbs;17079
This guide is intended to summarize the learnings i've made in the last several weeks, and provide a step based approach to upgrading your suspension.  Unlike other guides, I want to name products and companies and provide links to manufacturer webpages such that finding info on popular setups is much easier than it currently is.

 
Before beginning, please read the following threads of note:
Unabomber FAQ http://http://forums.nasioc.com/forums/showthread.php?t=911257
ButtDyno Suspension Upgrade Guide: http://http://forums.nasioc.com/forums/showthread.php?t=680651
 
 
STEP #1 - TIRE CHOICE
Yes, one of the most important parts of the suspension is your tires.  Tire choice will have an impact on the rest of the system.  
Read this: http://http://forums.nasioc.com/forums/showthread.php?t=400311


Step #2 - SPRING SELECTION
Select your desired ride height / spring setup. For many people (myself included) this was an difficult decision as there are no concrete rules, and way too many opinions/crap for a casual reader to sort through.  

Koni inserts have higher damping than OEM struts. This should be matched with a stiffer spring to avoid having an 'over damped' suspension system. An over damped suspension will also increase wear on the strut. Exactly how stiff you decide to go is a matter of personal choice and driving style.  Since the Koni struts have an adjustable damper, you can select many spring rates and still achieve a balanced setup.
 
Note that there are a few different spring sizes to be aware of:
http://http://forums.nasioc.com/forums/showthread.php?t=1170952
You will need tophats to match the spring, for example 2002-2003 springs need 2002-2003 top hats. 2004+ springs need 2004+ tophats.
 
Please see below for lists of available springs:
http://http://www.northursalia.com/techdocs/spring/spring.html
http://http://forums.nasioc.com/forums/showthread.php?t=695688
http://http://wrx.dicknogs.net/suspension/springrates.png

Note that there is a difference between STi Pink Lowering springs, and JDM Sti Pink springs as can be clarified by the following thread:
http://http://forums.nasioc.com/forums/showthread.php?t=637018&highlight=jdm+pink

Spring Stiffness Advice
Quite a few people will be more than satisfied getting STi Pink Lowering springs, USDM Stock STi springs, Prodrive springs, or other similar springs.  These springs are in the 200-225 lb/in range and are usually softer in the rear (example 225F/195R).  They are relatively cheap and easy to find.  Be careful of drop, as there are MANY springs out there that have large amounts of drop that may affect handling as described below. If these springs dont satisfy you, you can then graduate to a firmer spring.

Firmer springs include RCE, Ground Control, STi Tarmac springs or many others.  The stiffer springs are 250-300 lb/in range.  This category of spring seems to be acceptable daily drivers to young people, who dont drive long distances... catch my drift?  Not everyone will be satisfied with this stiffness, and you will see many mixed reviews with regards to daily drivability.  The quality of the strut/damper has a substantial influence on daily drivability.  Konis are argued to be of a great value and several respected NASIOC members suggest that you can tolerate a higher spring stiffness with a Koni than you could with some other strut brands.

Going stiffer than about 300lb/in should probably be done only by those experienced enough to fully understand the implications of that choice. The following is a good example: http://http://forums.nasioc.com/forums/showthread.php?t=1216361

 
Ride Height
 WRX's do not like being lowered. One reason is the suspension geometry and how it changes when the wheel is pushed up into the wheel well.  If you do decide to lower your car, do not lower it greater than 1" or you will encounter handling problems.  Below is a thread (page 2) that shows the location of the bump stops at 387mm ride height (stock), lowered by 0.75" (20mm), and then lowered 1.5" (37mm).  http://http://forums.nasioc.com/forums/showthread.php?t=1224029&page=2
As you can see... the car is RIDING ON THE BUMP STOPS.  This will effectively kill any chance of having a properly balanced spring/damper combo as the spring rate will ALWAY be changing due to the progressive bump stop. Why is this important? You will end up looking like a lowered honda civic bouncing down the road, and your overall traction and grip will drastically be affected on corners.  

See the below link for additional info on 'why lowering is bad'.  
http://http://forums.nasioc.com/forums/showthread.php?p=8457625#post8457625
 

Note that some users have had difficulty with after market springs where the spring will have excessive settle and cause a greater ride height drop than expected. Please fully research your spring before selecting.
 
Up to this point you should have accomplished the following:
1) selected a stiffer spring
2) verify the new spring ride height is acceptable
3) verify that the new spring will fit in your top hats (or see step 2)
 
STEP #3 - TOP HAT SELECTION
Stock WRX/STi top hats are very similar. The argument is that the relatively soft rubber in the WRX/STi top hat will deflect under load and affect the responsiveness of the entire suspension system. While this is true, Top hats are part of an entire suspension system and must be looked at in conjunction with the entire system.
 
Common top hat complaints:
- bounciness
- mushy/floating feeling
- bobble head
 
None of the above complaints are valid when evaluating the top hats alone. All of the above complaints are a complex reaction between the tires, their air pressure, the spring rate, the strut damping rate, and the flexibility in the top hat, and friction in the suspension system.
 
Generally speaking, if you just slightly increase stiffness, you may not need to upgraded your top hats. If you want a moderate-great stiffer spring, you should probably consider upgraded tophats. Switching to a lower profile tire, with a higher tire pressure will have a similar effect as a stiffer top hat.

Upgrading top hats will increase Noise Vibration and Harshness, however, most people imply that the NVH increase is worth the benefits.
 
Upgrades available include:
Group N top hats (stiffer than stock, available front and rear)
Race Comp Engineering non-lowering camber plates (front only) http://http://forums.nasioc.com/forums/showthread.php?t=821252&highlight=RCE+Camber
(any brand name) flat camber plate (available front and rear)
(any brand name) camber/caster plate (usually available only in front)
(any brand name) Pillow ball mounts (front/rear)
 
Camber plates may be required to reach the alignment specs that experienced/demanding drivers want.
 
Note that most camber plates and pillow ball mounts 'will' affect your ride height.
 
 
STEP #4 - Bump Stop Selection
Determine your bump stop requirements. With a stock suspension, at stock ride height, there is approximately 71mm of bump travel remaining in the strut. The Stock bump stop is 60mm long, giving the strut approx 11mm of travel before engaging the bump stop. This means when you brake hard the nose of the car dives down and will most likely begin to compress the bump stop. Many of you dont even realize your riding the bump stops.   This is why a progressive bump stop is important, as it will gradually increase in stiffness as you push harder and harder against it, preventing a hard bottoming out.
 
The OEM bump stops are progressive and soft. A wide choice of reduced height progressive bump stops are available at http://http://www.ground-control-store.com/products/description.php/II=10/CA=1
 
Many people are also creating ways to increase strut travel such as installing RCE non-lowering camber plates, or Koni Insert Lowering Spacers shown in thread http://http://forums.nasioc.com/forums/showthread.php?t=602326. Many people leave the OEM bump stop in place, or trim the top lobe off to reduce it's height if they lower by 25-30mm.

More discussion on bump stop requirements is available here: http://http://forums.nasioc.com/forums/showthread.php?t=1224029

Most of you wont be affected by Coil bind, but you should be aware of it.  Coil bind is when the spring is compressed to it's maximum and cannot physically be compressed further. The coils will stack up and hit each other.  coil bind is very damaging and should be avoided at all cost.  This is 'why' we all have bump stops.  

Up to this point you should have accomplished the following:
4) determined if you have enough strut stroke, or if you need to consider additional modifications to allow more strut stroke.
5) selected the size, shape, and firmness of your bump stop.
 
STEP #5 - KONI Insert Selection
This is an easy step. Select your Koni Insert.
 
INSERT PART NUMBERS
2002-2003 WRX (sedan)
Front 8610-1351SPORT
Rear 8610-xxxxSPORT
 
2004-2007 WRX (sedan)
Front 8610-1351SPORT
Rear 8610-1440SPORT
 
Note that 2002-2007 have very similar top hat designs for the FRONT only and 'should' fit universally with models of Front Koni inserts.
 
STEP #6
Remove existing struts from car
 
STEP #7
Dis-assemble OEM strut and install Koni Insert
 
STEP xxxx
install strut. Verify alignment and ride height.