JDM_Stig

iTrader: (3)

if its skitish how hard are your BC`s set ?

Linksfahrer

Ahh , again interesting , glad to see you have some progress.

I run Standard roll bars and my BC run Front with 6 maybe 8 clicks if im pushing it around on my own, I don't touch the rears much as I don't feel it makes as much difference as front so these are normally staying on 6.
the reason for not running 8 or more is if Im running slow through towns
it tends to just not to be as comfortable so 6 clicks does the trick.

My car never feels nervous, it does have that capacity on me though.

InTurbo

iTrader: (3)

Tried a few settings so far.
There set at 12 front 10 rear at the moment. This feels the best compromise.

14 front 12 rear makes the steering very light and unstable even on flat roads

10 front 8 rear is a bit soft and rolls on fast corners

8 front 6 rear is very soft and feels dangerous on fast corners

InTurbo

iTrader: (3)

What spring rate and ride height are you running?

InTurbo

iTrader: (3)

Took a photo this morning. As you can see it's not that low. 360 front 350 rear.
Also a pic of the control arms. They are horizontal. Not such a good photo of the front as it's hard to get under there.

JDM_Stig

iTrader: (3)

in the wet I run very close to ur softest setting and its awesome, absorbs the bumps with ease but still feels very planted,

You posted your camber & toe settings,
Front camber is 1.15
Front toe 0.03
Rear camber is 1.30
Rear toe 0.06
Is the camber actually -1.15 front and -1.30 rear ?
I know I run a little more camber then this with no tyre problems.

I run the Eibach ARB`s front and rear which from memory are 25mm rear and 23mm front.

InTurbo

iTrader: (3)

Yeah the camber is negative

Linksfahrer

I just checked my Sales recieipt Im wondering if mine are same rated as yours , Ergo if the spring rate is higher the damping will not be the same.

Mined are coded BC F-02-BR-Ra-6kg/5kg

I am aware that GDB are 4kg rated

http://www.bc-racing.co.uk/applicati...-ra-12956.html

As I have an MYO5 I m not using the
5/4Kg/mm Subaru Impreza GDB (Not 05+ STi) And therefore damper setting comparision is not useful , unless your using the same.

SouthWalesSam

iTrader: (1)

Because, BC coilovers aside, I'm running a similar front setup up to you on my bugeye wagon: Powerstation 'fast road' geo, Whiteline ARBs, Anti-lift kit, uprated brake discs, higher tyre pressures, Goodyear Eagle F1 Asymmetrics, etc.


I have been unhappy with the slow turn in, harder ride and reduced confidence from dulled steering feel.


Last week I chucked away my juddering, heavy-weight 'big brake' kit for a set of AP 6pots and discs.


The lighter weight brake setup saved several kilos at each corner. So, with lower unsprung weight I figured I could run lower pressures and, experimentally, I dropped my pressures back down to 34/33. Instant transformation!


Queue better ride, feel, flow and turn-in through bends and a much more confidence-inspiring steer. It's the closest that the bugeye has felt to my lovely old classic wagon. Just from changing the front brakes and tyre pressures....


So it was just a thought.

InTurbo

iTrader: (3)

Bit of an update. I raised the ride height today and I'm very pleased with the results.
The rear was 350mm from centre of hub to bottom of arch and front was 360mm

I have increased the rear by 10mm and the front by 20mm. (Bonesetters recommendations)
I took the car out for spin and even though my geometry is probably now way out there is a huge improvement.
Roll has reduced massively and the car feels a lot more stable at speed.

It's the best the cars felt since having the Coilovers put on, I was out for nearly an hour enjoying the car.
Really can't wait to get it booked in for another alignment and corner weighting now.

bonesetter

iTrader: (9)

Great news

Yeah, although your car didn't 'look' that low, as you crucially spotted your control arms positioning said otherwise

It always makes me smile knowing how the lower the car goes the more in rolls

-Nic-

iTrader: (4)

The more susceptible to roll it is. It may actually roll less if you've increased spring rates or anti roll bar resistance.

bonesetter

iTrader: (9)

Changing the pick-up points deals with RC lowering, then you don't have to alter arb & springs

2pot

iTrader: (3)

Do you mean fit the, badly named, anti-lift kit?
I don't know why anyone would want an ALK fitted to a primarily road driven car. Anti-lift is built into road car suspension for a number of reasons.
I'm not worried about alleviating flat-out, corner exit understeer - and if I was, I'd get stiffer springs and revised geometry, rather than intentionally introducing an increase in pitching, via an ALK.
Just my opinion; very interesting thread.

bonesetter

iTrader: (9)

Anti-lift and roll centre correction are very different

2pot

iTrader: (3)

You mean the Whiteline roll centre/bump steer kit? - that I do like - ONLY on a thoughtfully lowered car.

InTurbo

iTrader: (3)

This has been a good learning curve.
Done a lot of research today about roll centre and camber curve. And it seems Lowering a MacPherson strut suspension system to far causes more harm than good.

During suspension compression, if the control arms are horizontal suspension camber will go positive pushing the tyre on to its outside edge loosing grip in corners and becoming unstable over bumps.

Also having no downward angle to the control arms moves your roll centre further from your cars centre of gravity causing the lateral forces acting on your car to be greater causing more roll.

InTurbo

iTrader: (3)

As you can see from my earlier photo, I increased the rear ride height by 10mm and its given a obvious downward angle to the rear control arm.

bonesetter

iTrader: (9)

How have you been getting on now that you're on the slippery slop of chassis dynamics?

Happy with the car's handling/grip?

InTurbo

iTrader: (3)

Im booked in for an alignment later in the week, so will let you know how I get on.
Still deciding if to go with my original settings so I can do a direct comparison, or try something a bit more agressive.
Was talking to Simon at Chevron the other day and he runs slightly more Toe and camber on his set ups.

Also commented in me getting a roll centre kit and adjustable roll bar links before having him set the car up. Might do this depending how this next alignment goes.

bonesetter

iTrader: (9)

What sort of use does your car get?

If it's purely a hooner then why not go more aggressive on the geo? More camber and a little more toe-in?

If you're not doing many motorway miles then I would probably go with more negative camber up-front anyway

RC kit is not absolutely needed now your ride height is the way it is, plus the Whiteline kit comes with the bump steer stuff which is questionable whether it works at all (I wouldn't bother with that if it was me), plus it's pricey

There are other upgrades you could consider of course - increasing castor up front is always nice on the Impreza. The kit I would I would go for is the offset bush only and not the one which lowers the pick-up point

InTurbo

iTrader: (3)

The car is more of a weekend toy, but it does the occasional long journey for days out ect..
And I've not noticed any odd tyre wear on the current setting so could be set up slightly more agressive.

I was thinking of maybe
Front toe 0.06
Front camber -1.30
Rear toe 0.08
Rear camber -1.40

Linksfahrer

I run 1.5 camber front , which seems for my BC's to be just ok on motorway , more than this and you will start to sense that you have to hold the wheel , this effect becomes more pronounced in the slow lane where the trucks put tram lines into the tarmac. Id be wary of over doing toe in, although it gives a bit of a self centering effect , the tyre wear can be awful.

bonesetter

iTrader: (9)

For a weekender 'fast road' set-up as a rule of thumb I usually go about .5 deg less camber in the rear than in the front if you want the rear to be a bit more active, or equal. But I wouldn't really go more camber in the rear

I prefer max grip front (zero understeer) and a rear which can be trimmed on throttle to help with a line change etc

I would probably try and max out on front camber, so anything up to 2° will be fine. Your geo tech will need to slacken both clevis bolts front and rear (I believe the BC's have slotted holes for camber adjustment, so make sure your tech knows this)

As the rear suspension compresses on a GC and GD chassis, the wheels toe-out, so you need static toe-in to have zero toe when cornering

Something like this

InTurbo

iTrader: (3)

Thanks for all your input. That geo looks like what I'm after. Will post back when is all done.

piehole1983

iTrader: (7)

Very interesting thread. I'm refreshing a few bits on my GC, refurbing some STI shocks, new cusco anti roll bars, bushes etc and will obviously need to have the toe and camber checked out. I'm not wanting to lower the car at all by the way. My car is a weekend machine and won't be making many long journeys, based on this do any of you have a recommendation for toe and camber angles? Mostly normal driving with the occasional blast around some local twisty roads.

Arnie_1

It's so fun to watch Bonesetter at work. Good info there.

With that said, on a standard car, there is no better bang-for-the-buck upgrade than a larger adjustable rear ARB. You get less understeer, less roll and better rotation for very little money. All good and fun things. And with the adjustability, you can tune your setup for prevailig conditions.

The fun starts when you want to improve things further, when the suspension bug really bites! At this point you need to be honest with yourself and think about what you really want to do with your car before throwing parts at the car. Remember that its all a balancing act between: driveability, safety, maximum cornering, tyre wear, comfort and money.

One thing, back to the purpose of the large swaybar/arb advice ... it is very true that overly large bars combined with stiffly spring coilovers will definitely lead to a skittish, unsettling ride on a B-Road. Just lots of roll stiffness there, and some loss of suspension independence as well. I personally don't like to run big bars and big spring rates on a car that sees bumps and b-roads. They are no fun and are slow.

Using larger swaybars to tune suspension sort of came about because in the past, there weren't as many spring rate options available, i.e. coilovers were pretty pricey for Imprezas. So most folk only had one set spring rate (Eibachs, P1's, TEIN, etc.) and any suspension tuning and adjustment was happening at the ARBs, alignment and tyre pressures. They became the main way to quickly and inexpensively get results. With the advent of the cheap coilover, BC/Megan, etc. the average punter now had access to to spring choice. Unfortunately, the larger ARB philosophy remained and got mixed in with very heavy spring rates. Fine on a glass smooth road/track, absolute crap on a bumpy b-road. The more "mature" tuners out there are now picking milder bars when combined with heavy spring rates, or somewhat stiffer bars when combined with softer spring rates (as a very basic rule of thumb) but always in relation to the type of tyre they are using. The more stick, the higher the spring/roll rate. Of course, as Bonesetter has already aluded to, there are so many other aspects of suspension tuning (geometry, ride height, tyres, pressures, etc. etc.) that its tough to make blanket recommendations. It's why Bonesetter's initial question "what do you want to do with your car" is so important. For example, i would be less critical about handling issues when someone says, its a show car and boulevard cruiser. I#d recommend setup and parts that make his/her car look dope rather than blast them for using 2cm spacers and stretched tyres.

Linksfahrer

"I personally don't like to run big bars and big spring rates on a car that sees bumps and b-roads. They are no fun and are slow. "

Seconded Best regs Linksfahrer

bonesetter

iTrader: (9)

Arnie - good to see a post of yours here - just doing my best to hold the fort in your absence

Arnie_1

My one or two posts during the xmas break. I've been gone too long. Will try to troll the forums more often. I miss it.