john banks

Have started a new thread as we started to discuss this in my other thread, but thought this would open to wider audience.

I have 17" superlegs, Goodyear GSD2 fairly worn 215/40R17 soon to be replaced, bumpsteer removal, Eibachs and std MY00 UK dampers 30000 miles.

Have recently added rear ARB, solid drop links and strut brace to back and front upper brace to the front, plus a lower front brace is coming. 2 days ago fitted ALK and front solid drop links, and now the car stands on its nose during braking in the dry just before triggering the ABS, with the sort of braking you would do on track just before a corner. I have AP 4 pots on the front as I have had for some time.

Either the ALK (or less likely the droplinks) have absolutely murdered the stability under braking with the back end slewing in either direction under firm braking.

T-uk has similar setup but with KW coilovers.

I was quite happy with the standard dampers and Eibachs until this horrendous diving. Now I am stuck between taking the ALK off (assuming resetting the geometry doesn't help) or reluctantly buying stiffer dampers and throwing my ride quality away and making it even worse.

The ALK study that Whiteline commissioned suggested that in fact it completely softens the front end under acceleration and braking, and this is entirely what I do not want.

Anyone else experienced similar? I can see how it is anything to do with the power my car is running and far more to do with the ALK and good brakes not matching each other very well!

MorayMackenzie

IIRC, the Anti-Lift kit counteracts the cars standard Anti-Dive setup, so you have fitted an anti-anti-dive kit... hum... that would be a pro-dive kit!

Was never impressed with the ALK on my previous scooby, hence i wouldn't consider fitting one to this one.

RichiB

John

Did you get the alignment re-set?

Rich

T-uk

rich,

why would alignment affect lift and dive?

john's car is getting done this week ready for the new tyres but is actually handling well and braking in a straight line.

it is turning in better, holding the road better with a better balance with just a little understeer,probably a 1/4 of what it had.

RichiB

John:

I can't belive you are commenting on the handling of your car without getting the alignment done. When you fit an antilift kit it adds over a degree of toe out. "Get it set up"

Rich

john banks

Thanks Rich, will do. Didn't appreciate that it would be that sensitive to geometry. Maybe it will still dive but not squirrel about after it is done. I will report back.

[Edited by john banks - 5/13/2003 10:37:52 AM]

T-uk

well I am still confused why alignment would have anything to do with straight line lift and dive.

as far as I am concerned the car is handling better in corners than it was before (rolls a bit more due to higher corner speed) and will probably only get better once the geometry is done, however the only issue at this stage is straight line lift and dive.

I would also have liked JB to stiffen the ARB as a test just to see if it did balance the car better and loose a bit more understeer, although for john's driving style I think it is spot on at the moment.

GV27

Well it probaly wouldn't have any effect on a perfectly smooth surface. Unfortunately real roads are not perfectly smooth. So small undulations, bumps, cracks, etc will cause the suspension to move and the toe-out induced by the ALK install will make the front end rather unstable and want to dart around over the road imperfections.

The alignment will not effect how much the nose dives and lifts. So if John's goal is simply less front-end dive, then the ALK is the wrong product for him. Subaru built in anti-dive geometry for just that reason - to reduce dive. If, however, the goal is a more stable, grippier feel under braking, then the ALK with proper alignment should do the job for him.

The problem with the anti-dive geometry is that it has the effect of binding the front suspension up a bit under braking so that it doesn't follow small undulations as well as it could. Conversely, it holds the nose down under acceleration by adding a percentage (~33% according to Whiteline IIRC) of the sprung weight of the suspension/wheel/brake system to the unsprung weight of the nose - essentially it tries to lift the tires off the ground, resulting in less grip.

And yeah, I'm sure turn-in is great (maybe to good?) the way it is set-up now. Toeing out the front wheels is a common autocross trick designed to make the car easier to "flick" into tight corners. Unfortunately it makes it kinda squirlly for road use.

I believe that stiffening the rear ARB would make John's current problem worse.

Chris

[Edited by GV27 - 5/13/2003 5:09:26 PM]

john banks

Thanks Chris. Sums it up nicely. So the "softness" to put it simply helps with tyre contact which is a good thing. I don't mind the dive if it doesn't squirm.

T-uk

thanks chris,

the only reason I wanted to stiffen the rear ARB was to see if it dialled out the remaining understeer or caused oversteer although what is left is probably a safety net.

I still feel that the biggest dive /lift problem is due to weak dampers and possibly the progressive springs.

do you think linear springs would help?.

GV27

Yeah, I'm sure linear springs would help the dive situation as it'll squat down on the softer progressive initial rate right away even with gradual application of the brakes. Sudden braking will make this slightly worse as the nose already has downward momentum when it hits the stiffer rate.

Stiffening the ARB is a good way to tune balance, I was just saying to wait until the current situation is resolved - stiffer rear ARB is likely to make the back end skip around even more. A smaller front could also be tried. The STi setups actually incorporate a slightly smaller front ARB.

Wouldn't be surprised if the dampers are starting to give up. I certainly thought my MY'02 (UK MY'01) US dampers were starting to loosen up considerably when I swapped them over to Konis at 25k miles.

Chris

VinnyP

I have an almost identical setup but have Leda coilovers and had alignment and Anti bump steer done afterwards, don't get any of the problems you describe.

Vince

RichiB

GV27

"essentially it tries to lift the tires off the ground"

Oh Dear!!!!!!

Did you have any input into the handling of the cars on "Starsky and Hutch"?

Rich

Pavlo

hmmm, I think we've been here before. Last time the conclusion that the anti lift kit wasn't, and in fact was pro-lift and pro-dive, and that any handling enhancements came from increased castor.

At the time, I think Andy and I thought the way forward is not to use the ALK but to use topmounts to give the added caster without changing the lower wishbone angle.

Have you checked the alignment at the front? Toe out in paticular will lead to instability under braking.

Paul

GV27

I dunno about "pro-lift" and "pro-dive" but it certainly does eliminate the anti-lift/anti-dive geometry Subaru built into it. Whiteline has said that they are thinking of changing the name as the name is misleading.

Body dive and lift aren't necessarily bad things, and it is Whiteline's opinion (I concur) that a better way to eliminate body lift and dive is with dampers and springs. As I said above, the stock anti-dive/anti-lift geometry interferes with proper suspension action.

So it's my opinion that the small change in caster is only a small part of the story with the improvements gained with the ALK.

I wish I worked on Starsky and Hutch! I LOVED that show when I was a kid! BTW, we do have a guy here in the US who's highly modded WRX pops wheelies! Well, at least it did 'till his clutch blew up......

Chris

john banks

Original settings:

Front cambers -0.5 deg to 0.75 deg
Front toe in total 2.5mm
Rear cambers -1 deg
Rear toe in total 2mm

Adjusted front to to 1mm total toe out and it runs better in a straight line, the skipping has gone, and it understeers even less. I can feel the tail end starting to work, but under sudden lift off provocation it is friendly enough. Whilst the dive is still there under braking, the g-force under braking seems to have increased considerably with the slight toe out.

Andy F had a play after he set them up and seemed to like it.

Thanks for all the help gents.

vindaloo

John,

Just a thought.. The back end skipping about could be intermittent lockups. If there's more dive with the ALK (as currently fitted), then presumably that leads to a bigger weight transfer. So the back end could be unloading too much, leading to the brakes locking up. Alternatively the rear suspension might be running out of travel. (or a combination of both).

Vindaloo.

Andy.F

The dive under braking is mainly a function of the excellent AP's, good surface and slick tyres Even braking as hard as possible with one wheel on the white line/cats eyes it pulled up straight and stable.

I think the main problem was the excessive toe in (it was 5mm total) Now running with 1mm total toe out the handling is very predictable, instant turn in with mild understeer on power, even a sharp lift off mid bend just tightens the line slightly with no drama from the rear.

Oh, and it also goes like fek in a straight line too !!

Andy

Pavlo

5mm, eeek!

Yes, a fight between the front wheels as to which way to go!

Paul

T-uk

T-uk has similar setup but with KW coilovers. with about 140bhp less and no decent brakes at the moment

never felt this on mine but I did everything at the same time,JB's was done in stages. all I can say is that both cars turn in better and john's understeers less than before,my front end feels like it is on rails, even in the rain trying to provoke understeer I do not have any, the backend oversteers though probably the cr4p tyres on the rear and good years on the front.

as someone once told me "you can't polish a turd", in this case old,worn dampers with big power and good brakes.

you could always sell me the AP's and go back to 250bhp

edit to speak proper after reading it later.

[Edited by T-uk - 5/12/2003 10:47:04 PM]

GV27

The ALK will result in a bit more dive, which is probably accentuated by the progressive Eibach spring. But that shouldn't result in your problem.

My guess is that you're experiencing the effects of toe-out up front combined with a too-stiff ARB. The ALK introduces a bit of toe-out when installed that needs to be rectified - unless you're looking for an unstable ride (e.g. for autocross). A stiff ARB in the back will result in more off-throttle oversteer. Cobine an unstable front with a twitchy rear and you have the symptoms you describe.

To rectify this situation, first get an alignment done like you were saying. You might even want to ask for a slight bit of toe-in up front (like 1mm) to keep things more stable. BTW extra camber in front with a bit of toe-in results in a very stable grippy front end with good wear - the toe-in actually compensates for the extra camber from a wear standpoint (think of a rolling cone).If you have an adjustable ARB in the back try softening it up a bit as well.

BTW, I actually found that my ALK made the car more stable under brakeing -especially over bumps.

I find this link helpful when diagnosing and tuning out handling problems:

http://www.clubsi.com/suspension_tweak_table.shtml

Chris

[Edited by GV27 - 5/12/2003 6:44:00 PM]

john banks

I'll try not to prejudge it any more before the alignment is done then. Perhaps the dive wouldn't be so bad if it didn't skip about at the back. Driving a big French saloon underlines how minor it is in comparison, however, the French saloon's front brakes are pish

[Edited by john banks - 5/12/2003 6:49:20 PM]