Suspension fettling
22 March 2012, 07:59 PM
#1
Suspension fettling
Thought I would share what I've been doing recently on my STi wagon as things are coming together nicely 
Firstly. here she is
The car is rare, for a number of reasons - it's a new age STi wagon, it's white, has had a 'saloon' front end conversion (wings, bumper and front suspension), and as such has presented its own problems in trying to get suspension add-ons to work
The car came from Japan as you see it, with all the body kit, front end conversion, and a few other tasty goodies, namley pink STi pillow ball rear lateral links, braded brake hoses, and possibly a bigger turbo (it made 330bhp with just a de-cat).
From the get go, I found the handling lacking in precision, turn-in was a little vague, and there was quite a bit of squish/mush in everything - all quite typical I suppose of OE rubber bushings and std settings etc. For road use, I'm a big fan of a fixed perch option, which synergises the overall suspension feel, as coilovers don't, as well as giving a more organic, as well as dynamic feel. The car has the std STi red struts & OE springs, and runs std STi height.
I wanted to get the steering precision upto scratch first, and serendipously came upon a set of SuperPro front lower control arm polyurethane bushings, which included an offset camber bush, and also uprated steering rack bushings.
Caster was increased over 3/4° to 5° and I dialled in a decent geo setting (-2° camber all round, 0.06' toe-in all round). The result was a much improved front end feel. Steering weight incresed, as well as self centering. Increased straight line stability, a more refined steering feel and more feedback. Caster increases maintain dynamic geometry, so negetive camber is kept, as well as toe, but perhaps biggest of all is the inside wheel holds more traction mid-corner
nicely increasing front end traction and steering finesse.
The rear of the car was lacking though, and made more obvious by the improvements up front. It felt lose, wooly and rather squidgy and disconnected from the front. I moved the rear 22mm adj arb to its firmest setting which helped hold up the rear and reduce overall roll, but the front (& rear) still needed more. So I installed a front 20mm and a rear 22mm. These are now set to firm front, and middle rear (I initially set the rear to soft but with the firm front, had understeer). Now the roll was nicely controlled.
Things were coming on nicely now but still the rear felt wondering, and lacking precision. I picked up a set of pink STi trailing arms to complement the lateral links
The pinks can be seen from the side of the car now (I'll have the chav neon lights under there soon
)
Other thing I did is fit subframe lock bolts (WL)
The result was pretty good. The rear has tightened up a treat, and the car now feels connected front to rear, with a good level of precision through the wheel. Much less mush, much more instant feel.
A/B-raod munching is now superb Power levels complement nicely
Anything else? - yes, tyres. After all isn't this where a chassis starts? What's the point of getting it sorted and then using average tyres?
The Goodyear F1 Assy's on there are OK, but there's a fair bit of sidewall flex going on, as well as a squidgy mid corner feel & feedback. I'm going to fit my set of AD08's off the Type R. The Yoko sidewall is very stiff - the dry grip levels of the tyres are super glue sticky too but it's the precision I'll be keen to see...
Thanks for reading
Firstly. here she is
The car is rare, for a number of reasons - it's a new age STi wagon, it's white, has had a 'saloon' front end conversion (wings, bumper and front suspension), and as such has presented its own problems in trying to get suspension add-ons to work
The car came from Japan as you see it, with all the body kit, front end conversion, and a few other tasty goodies, namley pink STi pillow ball rear lateral links, braded brake hoses, and possibly a bigger turbo (it made 330bhp with just a de-cat).
From the get go, I found the handling lacking in precision, turn-in was a little vague, and there was quite a bit of squish/mush in everything - all quite typical I suppose of OE rubber bushings and std settings etc. For road use, I'm a big fan of a fixed perch option, which synergises the overall suspension feel, as coilovers don't, as well as giving a more organic, as well as dynamic feel. The car has the std STi red struts & OE springs, and runs std STi height.
I wanted to get the steering precision upto scratch first, and serendipously came upon a set of SuperPro front lower control arm polyurethane bushings, which included an offset camber bush, and also uprated steering rack bushings.
Caster was increased over 3/4° to 5° and I dialled in a decent geo setting (-2° camber all round, 0.06' toe-in all round). The result was a much improved front end feel. Steering weight incresed, as well as self centering. Increased straight line stability, a more refined steering feel and more feedback. Caster increases maintain dynamic geometry, so negetive camber is kept, as well as toe, but perhaps biggest of all is the inside wheel holds more traction mid-corner
nicely increasing front end traction and steering finesse. The rear of the car was lacking though, and made more obvious by the improvements up front. It felt lose, wooly and rather squidgy and disconnected from the front. I moved the rear 22mm adj arb to its firmest setting which helped hold up the rear and reduce overall roll, but the front (& rear) still needed more. So I installed a front 20mm and a rear 22mm. These are now set to firm front, and middle rear (I initially set the rear to soft but with the firm front, had understeer). Now the roll was nicely controlled.
Things were coming on nicely now
but still the rear felt wondering, and lacking precision. I picked up a set of pink STi trailing arms to complement the lateral linksThe pinks can be seen from the side of the car now (I'll have the chav neon lights under there soon
)Other thing I did is fit subframe lock bolts (WL)
The result was pretty good. The rear has tightened up a treat, and the car now feels connected front to rear, with a good level of precision through the wheel. Much less mush, much more instant feel.
A/B-raod munching is now superb
Power levels complement nicelyAnything else? - yes, tyres. After all isn't this where a chassis starts? What's the point of getting it sorted and then using average tyres?
The Goodyear F1 Assy's on there are OK, but there's a fair bit of sidewall flex going on, as well as a squidgy mid corner feel & feedback. I'm going to fit my set of AD08's off the Type R. The Yoko sidewall is very stiff - the dry grip levels of the tyres are super glue sticky too
but it's the precision I'll be keen to see...Thanks for reading
Last edited by bonesetter; 22 March 2012 at 09:32 PM.
23 March 2012, 02:00 AM
#2
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Thanks for your thread, its very informative, and you have the nicest wagon I have seen!
Do you think the front control arm bushes would still be of use when using coilovers, with or with out adjustable top mounts?
Also what exactly is fixed perch? As when I did a google search it came up with perches for parrots
Do you think the front control arm bushes would still be of use when using coilovers, with or with out adjustable top mounts?
Also what exactly is fixed perch? As when I did a google search it came up with perches for parrots
25 March 2012, 10:53 AM
#3
Hi Bugs, and thanks for the comments
To try and answer your questions...
The Super Pro pu bushings I think are a worthwhile upgrade whatever you're using. They are a big improvement over the OE rubber, especially if they have age is them, and the offset caster bush can also still be used whether you're using coilovers, or fixed perch ( strut & damper 
)
To try and answer your questions...
The Super Pro pu bushings I think are a worthwhile upgrade whatever you're using. They are a big improvement over the OE rubber, especially if they have age is them, and the offset caster bush can also still be used whether you're using coilovers, or fixed perch (
strut & damper )
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