Pink_Floyd

I've been having a nose under the car and it's obvious some of the bushes, links etc are fairly old. With that in mind I'm going to replace the ARB's, links etc. However what bushes and links can you change in situ and what ones require a geo-setup afterwards?

My plan is to;

Fit Whiteline F&R 22mm Anti-roll bars

Whiteline F&R droplinks

Look at the suspension

I'll then possibly look at an anti-lift kit. Poly bushes I'm not sure about?? On the Audi TT I had a while ago I changed the control arm bushes to the Poly type as they were a common problem. I'm clueless on the Scoob though.

I'm not massively displeased with the car's handling as it is, however it's clear to see 8 years worth of wear and I'm not going to line a main dealers pocket going the OEM route and I'm handy with a spanner so I'll give most things a go. Working 10 years on Tornados doesn't half make you good at working in the cold, pouring rain and getting your hands into really awkward places

budd

iTrader: (5)

Changing the ARBs is a very popular mod as it can decrease understeer and improve turn in, you won't need geo adjustment after fitting bars and drop links but for anything else polybushes, ALK, struts etc a check /adjustment will be necessary.
hovever before you do anything have a read here,
http://forums.nasioc.com/forums/showthread.php?t=171928
the Yanks have pretty much covered everything on here with lots of info and links to other sites.

dunx

iTrader: (3)

You might be better with a 24mm rear ARB if you are a smooth driver...

Monkeys like me use a 22mm fully stiffened up.

dunx

P.S. Do the ALK and the front bar together, one lot of labour... maybe the front wishbone bushes too ?

alcazar

iTrader: (2)

Isn't it true to say that if you want to get rid of the car's inherent understeer, stiffen up the back but leave the front?
So 22mm on the rear, or 22 front, 24 rear?

It's what I was told to do.

budd

iTrader: (5)

traditional thinking does indeed suggest if you want to fix understeer you want the rear to step out more. While this does work to some extent by improving the balance, I feel this is the wrong way to approach it. Sure CONTROLLABLE oversteer with the back stepping out is fun, and maybe even a good thing, but the front is still understeering and going wide. As part of this traditional thinking folks scream get a bigger rear bar, and leave the front alone or go smaller. I have to disagree on this. Here's why -

First, let's look at the technical reason. The dynamic camber curve for the mc'pherson strut setup is crap. It just is. That's a tradeoff of running this type of setup, and all setups have their good and bad points. What happens is this - you enter a turn at speed. Your ourside front corner gets loaded with weight. That weight compresses the suspension. When the suspension compresses the camber of that wheel, where that tire is loaded, rolls toward positive camber. If you're running very little static negative camber this will actually start to make the inside edge of the tyre light, reducing the width of your effective contact patch that resists lateral acceleration. This lose of traction results in that "push" or understeer condition. This is why folks who are more into performance run a decent amount of negative front camber. Sure, they give up some straight line accel and decel grip doing this, but that's more than offset by the fact that they can maximize the width of the contact patch in turns to help resist higher slip angles due to lateral acceleration. If you lower the car any with springs or coilovers that camber curve gets even worse. Oh, and the added bumpsteer sucks too.

So, how does this relate to the ARBs? The front ARB will increase the effective spring rate of the wheel without effecting the ride spring rate. In other words, it will help keep the suspension from compressing so much at the loaded corner. Less compression means less loss of camber. Less loss of camber means that you can tune to, and maximize the contact patch of the tyre to resist that push. Now, one of the things you need to consider - just like you can't make something from nothing, you can't make a good contact patch if you have nothing to give it to begin. Because the suspension will still compress some you need some negative camber in the front to start with. Camber bolts or adj top mounts help and there are various threads on alignment specs for a starting point.

Basically what we've got with the stock Impreza - a car that understeers and pushes the front quite a bit. Sure, you could throw a big bar in the rear and get the rear end to step out to help eliminate that understeer, but I feel that this is the wrong approach. The front of the car is still pushing, but the rear just happens to be stepping out at a faster rate than the front. The net result is a wider than what I feel is necessary lateral travel of the car. In other words, the rear is whipping around to point the front of the car where you want it to go, but the front of the car is still sliding sideways and taking the whole thing sideways making for a wider path than really is needed.

See, this stems from the philosophy that move oversteer does not necessarily mean less understeer. The front is still pushing. I feel the fix for this is to setup the front end of the car to truly reduce understeer as much as possible. This will make the front tuck in more, and while your tyres will be resisting more lateral acceleration taking more grip from straight line acceleration (think traction circle), you'll be able to unwind from the turn faster thus getting you back toward the acceleration portion sooner. In other words, you'll be able to drive a tighter, and more controlled line.

Additionally, by reducing understeer as much as possible you won't have to set up the car for so much oversteer. This will also lead to more control, a tighter line, and the ability to accelerate sooner.

Now, that's great an all, but if you're looking for a simple answer as to what size bar to get then here it is (I'm giving these in terms of whiteline bars as I am most familiar with them):

Rear - 22mm to 24mm, but if you go to 24mm then you really want to think hard about upgrading your springs. If you go higher than 24mm then you are taking the wrong approach and trying to fix shortcomings of your springs with swaybars, and this is not the right way to do it. Get a proper spring for what you do, and then fine tune with a swaybar.

Front - for the street and mild track work look at 24mm up front. If you start to get into it more then 26mm is good (WL makes a 24-26 adjustable front). These are also very good sizes if you are not a smooth driver as they won't make things too "darty" with super quick tuck of the front end into the apex. For hardcore track ****** who are smooth overall and can anticipate the "dartiness" then look at the 27 to 29mm front bar.

of course all this is very subjective what works for one isn't always right for another, for some the best option my well prove to be a slightly thicker rear bar but IMHO fixing the understeer is better than masking it's effects.

Pink_Floyd

Some great replies already

dunx

iTrader: (3)

My 2002 STI has 22mm both ends and coilovers, ALK and R888's, it doesn't oversteer or understeer unless the nut behind the wheel is loose...

On track mine just slides absolutely flat chat in third, so easily controlled even I can catch it... on the road it's just planted. End of. Anyone can induce understeer, but it's due to poor technique not the fault of the car, IMHO.

dunx

P.S. I doubt you'll be disappointed... BUT on a car as old as ours are, polybushing will only help things in general, when I get round to it, it's all getting painted too ! :LOL:

Pink_Floyd

I'm going to be doing lots over the next 12 months in stages. So I'll plan to do an ARB at a time and buy the bushes and fit the ones I can at home in stages too. I'm not sure about coilovers to be fair, I'm tempted but I'd like to keep some of the car OEM

JBala

Stage by stage is always a good idea! At least that way, you can see the improvements that each mod is making...

I have got Teins SS Coilovers already, and am looking to put 24mm rear arbs and drop links on Tuesday.

Will update the difference soon.

dunx

iTrader: (3)

I refer you back to the car's age... a while back I pushed mine to 400 bhp, had the R888's the uprated brakes and then loads more power, BUT in the "twisties" it all went pear shaped.

The 7 year old STI suspension just flobbed about and the car seemed to porpoise through corners as the ( mostly rear ) shockers failed to hold the bodywork under control.

I had to bite the bullet and swap to coilovers, or it was going to end up up-side down otherwise...

dunx

budd

iTrader: (5)

as the saying goes 'power is nothing without control'

Toffee

iTrader: (3)

Very interesting points, my 06 Spec C has Whiteline ARB's & ALK, with normal tyres (Ultrac Sessantas 235/40/18) my car with me driving of course understeers like mad I agree that with a LOT of effort I can get around the understeer, however I feel that it takes away from the outright pace I am trying to set?

Lee.

Ps. Still have standard shocks on.

Pink_Floyd

I totally agree Dunx,

Just not sure if I want to go down the complete coilover route, I'm sure someone suggested on another thread that you can buy OEM style adjustable shocks?

If I do go down the coilover route they're likely to be BC ones as they get a good write up for being fairly comfy in daily use. That said I'll try and ponce a few test rides in other peoples cars for comparison.

I might just save though and go for the Scoobyworld Stage 3 handling upgrade.

dunx

iTrader: (3)

555EFC,

have you played with the DCCD ( if fitted ! ) mine is set 40:60 all the time, except for the sheet ice & snow we have here currently... you could do to get the car set-up to suit your driving style ? Mine had too much rear toe once and it was unstable in the rain... at my age I don't want the bloody thing trying to kill me

P_F,

I know a couple of guys who fitted BC's and they are very pleased... Bren @ Apex is just down the M62 from me. Sadly I got some Teins from him, that are just a touch too stiff for the mean streets of South Leeds, but are superb on track.

All IMHO.

dunx

dunx

iTrader: (3)

I "had" control at 340 bhp, the extra 60 sent it pear-shaped...



dunx

Toffee

iTrader: (3)

Your right fella, first track day I left the DCCD in auto and the tyre pressures at 34psi when cold. After this 1st outing I was informed to have the DCCD in dry 2 up from bottom in green & wet 4 up from bottom in 2nd orange. I also had the rear ARB moved to another setting to help and adjusted tyre pressures to 25psi cold = 34.5 when warm with Ultrac Sessanta's. (on a pretty damp track)

Although this helped it was still awful, although I aint Lewis Hamilton I think I am ok? but the ability to just "ATTACK" the track was ruined because of the understeer. The day/s were dominated by trying to over come this issue and trying to change my driving style to drive around this problem > car is 420bhp....? not that much really (See BHP leader board )

I believe that this is an inherent problem with either imprezas or my driving style? I have concluded that my driving style does not help......but the car needs a complete chasis overhaul to avoid understeer see my Time Attack thread in Projects


Lee