Suspension Information Compendium -what fits, tuning info

Struts, spring, anti-rollbars, braces and the like.

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scottzg
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Suspension Information Compendium -what fits, tuning info

Post by scottzg » Tue Sep 23, 2003 8:40 am

PLEASE ADD NUMBERS TO THE CHART, AND LET ME KNOW IF SOMETHING IS INCOMPATIBLE!

labelled strut assembly
Image

Stock and aftermarket bars and spring rates
Swaybars:
...................................Front.........................Rear
legacy wagon................18............................16
legacy wagon awd.........18............................16
legacy sedan.................18............................16
legacy sedan awd..........18............................16
legacy turbo W..............18............................18
legacy turbo S...............18............................18
legacy W w/ air susp......19............................18
legacy S w/ air susp.......19............................18
impreza base S................?............................DNW
impreza base W...............?............................DNW
impreza 2.5 RS S.............?............................DNW
impreza 2.5 RS W............?............................DNW
WRX later design W.......................................17 does it work?
WRX W.........................................................17 does it work?
WRX later design S........................................17 does it work?
WRX S..........................................................20 does it work
Whiteline........................22...........................18-20-22 (adj)

Springs:
..........................................Front............................Rear
.....................................rate........drop.............rate.........drop
legacy wagon.................123..........0"...............179...........0"
legacy wagon awd..........134..........0"...............190...........0"
legacy sedan..................123..........0"...............129...........0"
legacy sedan awd...........132..........0"...............132...........0"
legacy turbo W...............134..........0"...............190...........0"
legacy turbo S................132..........0"...............132...........0"
Whiteline
wagon...........................176..........1"...............131-218 progressive (pg)...1.5"
The following require different front spring seats.
impreza base S.............softer front springs
impreza base W............softer front springs
impreza 2.5 RS S..........157.............1"............ 149........1"
2002 2.5RS (MT/AT)......149/158 ......................117/129
WRX Sedan (MT/AT)......163/163 ........?............119/132......? fr
WRX Wagon (MT/AT).....163/163.........?............132/144......?
Eibach..........................171 ............................91-188
Tein Soft......................67.2-179.18..................61.59-179.18 pg
Tein Medium.................67.2-235.18..................61.59-218.38 pg
Tein Hard.....................307.98 ........................279.98
H and R........................196.25-204.1 ...............186.25-193.7
Prodrive P1...................215.............................195
GDA STi Sport Springs...200.............................185
2004 USDM STi.............224..............................194
2002-2003 STi "Pink".....215..............................190
2004 STi "Pink".............257 .............................217
SPT/STi.........................217..............0..............190.............0
STi Version 4................196..............................174
STi Version 5................224..............................185
STi Version 6................237..............................195

Coilovers:
DMS 40mm Street/Gold..225............................180
DMS 50mm Rally............275 ...........................225
DMS Tarmac..................700............................650
DMS 60mm Super Strut..260............................200
GAB Revolutions II.........335............................280

Struts:
...............................adj max%.......................adj min%
Gabriel..........................0....................................0
Monroe..........................0....................................0
KYB GR2.....................+15................................+15
KYB AGX
1 - Same as Factory .........................................+00
2 - Same as GR2 ..............................................+15
3 - 50% firmer than #2......................................+72
4 - 30% firmer than #3.....................................+123
Koni Yellow....................?....................................?
SPT/STi......................~+70.............................~+48
( SPT struts give slight positive camber in rear, need rear camber bolts.)

Notice that some aftermarket sedan numbers added have a heavier front spring rate. This is because the springs are meant for a GC or GD Impreza. Stock Legacy information is from my 1990 FSM. Info might have changed over the production years.

Keep in mind that the amount of preload is not listed, so this isn't a perfect guide and what may look like a poor fit may or may not be so. See here for a discussion on the topic.

converting to later model strut assemblies
If you have a....And want strut/spring combo......Then you need
90-91 AWD....GC/GM/GF (93-2001impreza)........FP, RP
.......................GD/GG (2002+ Impreza)................FP, RP, SPT
.......................BD/BG (95-99 legacy)....................FP, RP
.......................BE/BH (2000- legacy)....................Probably FP, No fit rear!
.......................SF (98-02 forester)........................Probably FP & RP
.......................SG (03- forester ...........................Probably FP & RP
.......................BC/BF fwd.....................................Struts Don’t Fit!

92-94 AWD....GC/GM/GF (93-2001impreza)........FP
........................GD/GG (2002- impreza)................FP, SPT
........................BD/BG (95-99 legacy)...................FP
........................BE/BH (00-04 legacy)...................Probably FP, No fit rear!
........................SF (98-02 forester)......................Probably Nothing
........................SG (03- forester...........................Probably FP
........................BC/BF fwd....................................Rear struts don’t Fit!

FP = Front Upper Spring Perches, RP = Rear Upper Spring Perches
SPT = Might need washer between rear top nut and top mount.

The difference between 90-91 and 92-94 struts is the height where the spring seat is welded to the strut. See http://www.bbs.legacycentral.org/viewto ... yb+fitment
swapping which springs and struts from what years you use you could raise or lower your car and maintain factory suspension stiffness.[/url]

general information on suspension tuning
This little primer will discuss various options and what actual changes are taking place, albeit with too many generalities and without enough detail.

First thing to understand is that ‘improving the handling’ could mean several things; making the suspension stiffer and more sporty, making the controls more precise and limiting bushing deflection, and altering the balance of the car to encourage it to behave differently to inputs.

A sporty ride is usually accomplished by changing shocks (or in our case, struts, same thing) and springs in for stiffer ones. Oddly, going to a stiffer strut is going to provide a bigger improvement in actual handling prowess, especially as the vehicle’s speeds increase and the wheel movements get larger. Most oem struts are designed to be most effective at low speeds and provide soft ride with the springs they’re matched to, so finding a more stiffly valved shock designed for oem springs can be a worthwhile exchange. Keep in mind that stiffer springs tend to prefer less compression and more rebound from a shock, so while a single adjustable shock is an improvement, it still might not be the ultimate solution. It will provide a degree of tunability that a fixed damper won’t allow. Of course, if you don’t want to be fiddling with the settings, a shock/spring set might be the most sensible solution.

Springs are the most popular modification made to a car’s suspension. Aftermarket springs can be of a different length, stiffness, or of variable stiffness. A longer spring will be compressed on the strut even before the weight of the car is on it. This makes the spring feel stiffer than it is, especially before weight is transferred to it from cornering. Variable rate springs use wider and narrower coils, or taller and shorter coils to make the spring rate change through its travel. An effort by the designer to make the spring suit a given shock, or provide improved ride quality while still resisting body roll. There’s just no simple formula to apply to how a spring will ride or make the car look. Lowering the car looks great, but it has some trade offs. The main one is that generally it moves the roll center away from the car’s center of gravity, actually increasing roll. Subjectively, this isn’t noticed, since the person is sitting lower and doesn’t feel the sway as much. The effect is somewhat curbed by the stiffer springs’ resistance to roll, as well. Another problem is that the struts gain less and less negative camber as they are compressed. The first inch of travel that is lost lowering is the inch with the most negative camber gain. This will be discussed later. The last problem is that the stiffer suspension reacts more harshly over bumps, meaning a rougher ride and bumps in a corner upset the chassis more. On the positive side, the stiffer springs do reduce suspension movement, keeping the suspension in the ‘sweet spot,’ better. The stiffer suspension also allows the weight of the car to transfer faster, so the driver doesn’t have to wait as long for the car to react before he can make his next move. This makes for a nimble feeling and gives the driver more space to correct from bad inputs, although it gives less time to react. Once lowering springs are fitted, be sure to get an alignment, as the lowering affect camber and toe.

Swaybars, or anti-roll bars do the same things the coil springs do; they reduce body roll and (anti-roll bars are really just torsion springs) increase the speed which the chassis reacts to inputs. Word on the street is that swaybars are twice as effective at limiting roll as the springs are. They’re cheap and super easy to swap, so a casual racer could have a couple lying around that they swap for changing conditions to increase a car’s tendency to oversteer/understeer. The adjustable ones are pretty cool too. Of course they have some drawbacks as well; big roll bars can pick up the unweighted inside tires, they unsettle the opposite wheel when one wheel hits a bump, and since their spring rate is dependant on weight transfer, it’s impossible to have them perfectly damped all the time. Basically, they suck off road.

A car that reacts precisely to the driver’s inputs is much easier to drive quickly, even if its limits are low. A communicative car involves the driver, or whatever. Simply put, taking out the slop in the suspension will, well, make the car less sloppy. First off, even on an old car, if the ‘controlX feels like crap’ something is busted or worn out. Fix that first before trying to modify other parts to conceal it. Steering racks moving in their mounts and improperly bled brakes are classic examples of this. The best thing, once sure that the car is in good repair, is to get some good tires with a nice stiff sidewall. Having the stickiest rubber isn’t that important, although large tread blocks tend to provide better feedback. Polyurethane steering rack bushings are wonderful for steering feel, and fresh brake fluid can make a profound difference for braking feel. High performance brake pads, however, usually feel like crap unless they’re being used for their intended purpose. If they’re not getting hot, they’re not worth sticking on. Never cooked your brakes? Leave them alone. Driveline bushings reduce the lag between driveline movements and wheel movement, with the tradeoff of some nvh. Polyurethane bushings should be avoided anywhere where there is movement inside the bushing, for example, on lower control arms or C style endlinks. The urethane does not twist like the rubber does, and so the bolt will wear the urethane loose over time. Stiffer rubber (measured by the durometer) is a better solution. Stiffer rubber bushings in the suspension arms reduces dynamic toe and camber change due to load, making for an easier car to place. NVH is a trade off, of course.

The following is all about oversteer and understeer, and the common ways to tune for both. First off, a car will exhibit different characteristics at different speeds and radius turns, due (among other things) to power, lift, and suspension geometry. Some modifications affect oversteer/understeer all the time, like swaybars, and some only under acceleration or braking, like brake valving.
Really, the balance of the car should not be tampered with by someone who cannot comfortably and safely explore the character of the car before and after the modification. A inexperienced commuter driving an oversteering beast is only waiting to get bitten, and is probably not aware of what they’ve done. That said, most cars are set up to understeer endlessly and will never allow one to explore the balance. To get a legacy to exhibit some lift off oversteer while still being fairly toothless, a 18mm swaybar or -1.5 degrees of camber in the front with 0 toe all around will do the trick. The alignment won’t affect tire wear significantly. Both together is what I run on the street, and it’s proven to be easy to live with and fun, although I’ve had to catch the rear end several times when the trunk is loaded.
The basic idea is to give one end of the car more grip than the other; a car with more grip in the rear at any given moment will understeer, more grip in the front will oversteer. The driver can transfer the weight of the car around and control the balance this way. Stiffening one end of the car will generally reduce grip. Stiffer springs, shocks, swaybars all do this. The exception is that if the parts keep the wheel in better contact with the road, the grip actually increases. An example of this is the front swaybar- a big front sway will cause understeer with jerky inputs, as the weight transfers quickly and overloads the tire, but once the wheel is weighted, the bar keeps the wheel in the sweet spot of its travel.
Stock cars are designed with about 10% more braking to the front than rear, regardless of a sporting intent. Once the car is spinning under braking, the effectiveness of the brakes is significantly reduced. You want a car that understeers under braking. A car with sport tires and/or properly damped suspension is going to be able to stop better, transferring more weight to the front; most modified cars already have more oversteerish brakes than the manufacturer intended. Be aware.

This was written off the top of my head while I was stuck with my laptop at a bus terminal. Consider the source. Comments and corrections are appreciated.
Last edited by scottzg on Sun Sep 03, 2006 7:25 pm, edited 37 times in total.
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Post by Yukonart » Tue Sep 23, 2003 8:56 am

WOW! :shock:

Nice job! Now that is some useful information! 8)

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Post by Grant » Tue Sep 23, 2003 3:09 pm

Everywhere I've always looked has the front springs for FWD and AWD sedans using the same part number. Is that just a mistake or a shortcut they take and their is no telling what rate springs you'll end up with for the front. Anyone know if the back springs are interchangeable between FWD and AWD with GR2s? I'm going to go the junkyard on Thursday and if I find a AWD Legacy I may just take the springs off to compare with mine.
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Post by scottzg » Tue Sep 23, 2003 6:39 pm

my figures that i have added are from the 1990 fsm. It's possible that it was changed later (perhaps when they got rid of the stupid tapered springs?)
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Post by Golden Oldie » Tue Sep 23, 2003 9:57 pm

Excuse my newbieness but what's a swaybar and what does it do please?

How do the figures above work too?

All I know is that I have a 1991 1.8GL UK Spec and need to at least stiffen the ride if not lower it aswell as it rolls in corners like a pig in mud!!

Cheers, Jon
1991 Subaru Legacy 1.8GL 5MT AWD Sedan...in Gold :D 118,881 miles and counting...

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Post by ciper » Tue Sep 23, 2003 10:49 pm

Sway bar helps to reduce sway. It acts to couple the left and right suspension. When you turn the outside of the vehicle wants to lower. The sway bar transfers some of this and "lifts" the other side.

It helps to keep the vehicle settled, so your transition between weight distribution can be quicker. It should be matched to your suspension though, too large of a bar with soft suspension works the bar extra hard and the attachment hardware pays the price (crushed bushings, broken mounts)

Changing the ratio of sway bar size between front and rear can modify your vehicles overstear/understear nature. Usually moving the ratio towards the rear helps create more overstear while moving the ratio to the front creates more understear.

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Post by LaureltheQueen » Tue Sep 23, 2003 11:01 pm

My 91 wagon has 19mm rear sway, and as far as i know, my suspension's bone stock.

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Post by scottzg » Wed Sep 24, 2003 3:02 am

are you sure about that? I am reading the factory service manuals
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Post by Legacy777 » Wed Sep 24, 2003 2:48 pm

Anything's possible.....the FSM's are known to be wrong.......however I really have not heard of any 19mm rear bars on subarus
Josh

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Post by Grant » Wed Sep 24, 2003 3:55 pm

I just had another idea from this. Ciper did some research on spring diameters for different models. We should put that in here too. I checked 1stsubaruparts.com and they list the same spring for 90-94 Legacies. But then again that doesn't mean that it is right.
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Post by LaureltheQueen » Wed Sep 24, 2003 5:48 pm

uh, we measured it when subaru tried to dick me around with sway bar bushings.

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Post by Legacy777 » Wed Sep 24, 2003 11:44 pm

LaureltheQueen wrote:uh, we measured it when subaru tried to dick me around with sway bar bushings.
can you acurately measure 1mm ;)

The paint, gunk, etc adds to the thickness too.

Not tryin to say you're wrong, just making sure the correct info gets out there.
Josh

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Post by scottzg » Tue Nov 25, 2003 3:36 am

updated
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Post by legacy92ej22t » Tue Nov 25, 2003 4:24 am

Right on scottzg! Very good idea. :D
-Matt

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Post by scottzg » Wed Dec 03, 2003 9:41 am

updated again- added info for agx struts. # is percentage over stock, per setting. Also, please note that the GR2 figure of +30% is wrong, GR2's are only an increase of 15%. This information was obtained directly from kyb, via email.

Would anyone else like to tackle koni?

Mod- a sticky would make me happy 8)
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Post by Legacy777 » Wed Dec 03, 2003 3:31 pm

kyb told me the gr2's were +20% stiffer
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Post by DOA » Wed Dec 10, 2003 10:52 pm

Hey Golden Oldie, just to clear up the yankisms, a swaybay is an anti roll bar m8. Just btw, if your after only slightly stiffer suspension then you would probably be OK using stock Turbo parts. Saying that though I know I need stiffer suspension on my turbo but just cant find any aftermarket stuff over here to suit the legacy, its always imprezza this, imprezza that, youd never think McCrae won so many rallies in a legacy. If you know of any good places to look give me shout. Oh and did you find anywhere that did exhausts?
If only I hadnt bought the bike, this would feel fast :P

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Post by vrg3 » Tue Mar 09, 2004 5:53 am

I've got a little info to add... Here are scans of the parts sheets telling what cars were originally equipped with what spring part numbers. If someone wants to distill these we could figure out exactly how many different types of springs were actually manufactured.

http://www.graphics.cornell.edu/~v/springs/
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Post by ciper » Tue Mar 09, 2004 5:57 am

Dang, there are so many part numbers even for vehicles that use the same spring! I counted at least 10 different parts for the front alone. I dont think that page is accurate.

My understanding is that there are
2-3 front sedan springs
4-5 rear sedan springs
3 rear wagon springs
2 front wagon springs

Assuming the turbo cars had the same springs as the NA versions.

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Post by THAWA » Tue Mar 09, 2004 8:05 am

if it matters my front struts are 20313aa130lh and 20313aa120rh
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Post by vrg3 » Tue Mar 09, 2004 3:35 pm

ciper - You think the parts catalog is wrong? I haven't seen many errors in it before... It's possible that some of the later part numbers supercede the earlier ones though.

And it does look like turbos had different springs.
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Post by ciper » Tue Mar 09, 2004 8:27 pm

Not wrong exactly, some of the part numbers may be that the spring has better weather resistant coating or with a different plastic noise guard or something. Not that the rates or height is different.

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Post by vrg3 » Tue Mar 09, 2004 8:48 pm

Yeah, that's probably the case.

I actually just found an error in the Subaru parts sheets this morning... It has to do with the turbo oil fitting banjo bolts. I'll probably be asking a question about it in the Turbo forum shortly. :)
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Post by ultrasonic » Thu Apr 29, 2004 7:08 am

Add to suspension chart...

91 Legacy Sport Sedan front sway bar = 18mm
-steve-

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Post by britman » Tue Jun 29, 2004 6:38 am

Golden Oldie wrote:Excuse my newbieness but what's a swaybar and what does it do please?

How do the figures above work too?

All I know is that I have a 1991 1.8GL UK Spec and need to at least stiffen the ride if not lower it aswell as it rolls in corners like a pig in mud!!

Cheers, Jon
in england its called the antiroll bar !! :wink:
yeah she looks good, but someone somewhere is tired of her crap !!!!!

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