Reducing under steer on 1997 Classic sti jdm
 

Evening all.
I've been struggling a little with the above vehicle ( 1997 jdm sti ) it's on std suspension and wheels with federal 595rs tyres and I'm looking to improve on the front end under steer if possible without breaking the bank as it's a third car (much to my wife's disgust) :)
Any pointers would be most obliged .

There's many threads on here about this type of thing, have a quick search through them. There's also a member on here called 2pot who's big in to suspension improvements who will be able to advise you.

Yea thanks buddy , I had a good mooch/search about over the last few weeks but no definitive answer to reducing under steer , I'm worried that I chuck aload of cash at coil overs or anti roll bars and potentially non will improve my old girls front end slippage or I buy the wrong bits or kit and make it worse . .

Well I think if you fitted a larger rear ARB you'd be on the right track straight away. Have a look in the parts for sale for some and also some better drop links too. I have a 97 UK car and went all out with WR97 Bilstein struts with uprated bumps stops inside, new P1 springs with slightly lower fronts, Cusco front and rear ARBs, Whiteline and FloFlex drop links and various poly bushes. Unfortunately I haven't used this setup as yet but on paper it should be good!

Yea sounds like you've got all angles covers there mate , "on rails "springs to mind if you'll excuse the pun :)

lol

Yeah I've been gathering up the parts over time and refurbishing them along the way. The Bilsteins are as rare as a rare thing!

You might want to pick up a set of the later "red" STI inverted struts. As far as I know the earlier STI cars have normal black struts found on the UK cars also.

I'd fit whiteline kca335 front top mounts - in the max caster/max camber orientation.
https://www.kamracing.co.uk/whiteline-kca335.html

Front:
1 deg 45mins negative camber, per side - more or less negative, depending on wear
zero toe

Rear
0.15mins toe-in, per side.

What tyre pressures? Increasing the rear pressure will help.

Any more depends on budget.

First id look to replace the almost 20 year old rubber bushes,
then see where you`re at.

Also, check the condition of your rear bump stops.

Thanks for the replies guys, I had a quick inspection of the suspension doesn't seem anything a miss albeit I can't check the composition of the bushes but there didn't seem to be a huge amount of movement . The car only has 50k on the clock , I'm wondering if it's me jumping from one car to the next and it being just a traits of the gc8 rather than a fault with the suspension it's self , my every day car is a e92 msport and my other a Renault 5 gt turbo lol so quite a leap between them .But from the e92 to gc8 the gc8 does seem sloppy and bouncy.
Thinking it may well be a shocker issue at worst .

I'm wondering if it maybe worth changing the shocks and springs inc top mounts and swap out the rear anti roll bar for an uprated 24 MM to start .

Appreciate all your advice !

In general, especially compared to your BMW, these older cars will feel sloppy. Steering will be slower, also contributing to a lethargic feeling compared to the new car. It seems like this is can be your "fun" car, so no real reason to worry about tyre wear, i.e. you can go more extreme on your alignment to get the car to grip properly.

As the others have said, fresh bushings, respectively STi Group N or Poly from Whiteline or Super Pro at all the critical points (front transverse link bushing {also known as the ALK}, rear lateral links and trailing arm, and steering rack bushing) would go a long way to freshening up the ride and adding a lot of precision to the handling. This is, however, a fairly cost intensive operation, lots of labor. But definitely not to be underestimated in its overall contribution to great handling. It is amazing how much movement there is in the OEM bushings under cornering, acceleration and braking load. Because of this movement your geometry under dynamic load is seriously compromised, and leads to, among other things, lots of understeer.

Geometry. One of the most effective and important handling mods you can do to your car. Its basically the first thing I look at and change when I bring car home. Using the stock adjustments, take a look at Bonesetter's geo specs he has posted. Getting the max negative front camber you can from the OEM camber bolts will go a long way towards helping with understeer. Max with the OEM camber bolt is about -1.5º. Rear is not adjustable for camber but you can loosen the lower clevis bolts and there is a bit of play there for you to reduce the amount of camber there and even things out, side to side. Toe is a personal thing but its worth noting that a bit of toe in helps with steady state cornering and mid corner and corner exit grip. Caster is also an overlooked mod, geometry wise. Increase this if at all possible. You can do this through caster bushings or anti lift/caster kits from WL or SP. There are other ways to increase caster such as through camber plate rotation and, if you have the aluminium front wishbones, the "free caster mod".

Anti Roll Bars: Great, cost effective way to reduce roll, reduce understeer and alter rotational balance of the car. The UK market likes to run 22mm F/24mm R bars. I personally like 22mm F/R.

Springs/Dampers: Quite possible your dampers and springs are knackered. Cost effective is just freshening up the dampers and keeping the OEM springs. They are great for B-Roads as they have lots of travel and the damping is fairly decent but can have a bit more roll on smooth tarmac. There are loads of inexpensive coilover setups out there. None of which I'm personally a big fan of.

Tyres: Get the best tyres you can afford and appropriate for the weather conditions. Sidewall stiffness is also a taste thing. Some high performance tyres have "softer" sidewalls compared to other inexpensive brands, leading some to feel like they are less precise feeling. Like I said, its pretty subjective there.

Driving style: "The most important nut to fix is the one behind the wheel!" Actually the most important modification you can do is with the driver. Learn to drive this car. Driving style and technique is the most common cause of understeer in an impreza.

Struts:
Excel-g's -£250
Agx adjustable - £505
Koni adjustable inserts -£600 + cutting and prep of your existing struts
V5sti/v6sti/P1 inverted - £850

Springs (I'm biased):
P11L - £235 - Rate as P1
WR15R/T - £290 - 230lb/in 200lb/in
Both the above come with understeer-reducing, matching bump stops (for inverted and non-inverted dampers - £45/£50) - allowing you to use less rear bar.

Bars:
undulating/uneven roads - f19mm/r20mm
smoother/flatter roads - f19mm/r21mm adjustable or r22mm adjustable
track days (with stickier tyres) - f22mm adjustable/r22mm adjustable

24mm rear bar (double the stiffness of a stock 20mm bar):
You'd better understand trail braking, lift-off oversteer and a definite hindrance on the road in poor conditions/emergency braking.
In addition, you'll have to use struts capable of controlling the 24mm bar + the spring rates. Otherwise you'll be under-damped, creating excess heat and premature wear of the dampers.