Alberick

Can anybody explain me please waht is the bump steer mod? Is anything being removed from the car and how does it affect the car?
Better handling, more power?

Thank you for any help

Al

Hoppy

Al, bump steer is a 'safety' feature built in to the steering geometry. When cornering hard, the front wheels will toe-out promoting understeer. This is easier to control than oversteer if you over cook it, making the car easier to drive.

But this toe-out also dulls the steering response and impares on the limit handling. Power Station adjust the steering rack to remove this understeer, as well as resetting the geometry on all four wheels.

The result is said to be dramatically improved turn in and steering feel. The downside is that having a sharper front end makes the car more liable to lift-off oversteer at the rear. So not recommended for inexperienced drivers.

I'm having my car's bump steer removed this weekend, soon to be followed by a day on Don Palmer's 'Wetter the Better' handling course.

There's loads more info on the site. Type in bump steer and do a search.

Hoppy

K921SGC

Had it done last Friday and its the best mod ever.Takes a couple of hours, steering rack is lowered using precision shims, and front and rear geometry is setup exactly using an extremely accurate laser aligner.£100+vat less than the price of a tyre, transforms the way your car drives ,no understeer.Give the powerstation a ring .Bob mac

NIGE K

Hi Hoppy
Do you know if this mod would work on a P1 as I would like to sharpen up the front end response.

Cheers

Nige K

PeterPerfect

Gets my vote...along with the ALK.

Trout

iTrader: (1)

In my own experience of living with the revised Bump Steer geom for six months I would say that on road and track the (Sti V) is a much better drive.

Corner to corner it is much more fluent (makes up for my driving) and as an inexperienced driver I have not had a single white knuckle moment attributable to the revised suspension. This includes driving fairly hard at my first ever track day which was very, very wet - at Castle Combe - a track with zero tolerance to errors.

The Bump Steer removal is a significantly greater improvement than the Anti-Lift Kit AND Prodrive geom combined.

The added benefit is that with the Bump Steer removal you can run a lot less negative camber (minus 0.5 deg comapared to inus 1.5!) thus getting more even tyre wear, if this is a consideration.

I would strongly recommend it for the P1, however I also believe that the P1 already has an anti-lift kit style revision to the dynamic castor, so it may be that the ALK is not required.

I have both and they work very well together.

R

Hoppy

Nige K, as far as I'm aware (and I'm no P1 expert!) the bump steer removal and other suspension tweaks should apply to a P1 as much as to any other Scoob.

But I would take things one step at a time. It's very tempting to go to PowerStation and have the bump steer done, anti-lift kit fitted and stiffer roll bars as well. But if you do that you'll never know which component or other is making the difference.

I had the bump steer mod done on Saturday and endorse everything people have said about the PowerStation crew. They are really top flight guys. And the bump steer mod works for sure, though I have to say it isn't the miracle I'd been led to expect.

As I see it, the problem is that Imprezas are prone to understeer, which is no surprise given that it's a front engined car with front biased four-wheel-drive. It's a well balanced package which readily lends itself to going fast in less than ideal conditions.

But it ain't no race car and if you take these modifications to extreme, yes, you will end up with a car which goes exactly where you point it but with a rear end that is clinging on by the skin of its tyres. Make a mistake and it'll snap round on you big time. Every change you make at one end has an effect on the other. It's a simple trade-off and you can't have both.

My car has Prodrive struts and springs, and now the bump steer mod and geometry in place of Prodrive settings. I like it. I feel the front-rear balance is about where I want it - good turn-in but a back end which retains a significant degree of grip. Any further changes will be carefully considered over winter (hopefully, Stef will try them first so we can all learn at his expense!).

But let me say this. Suspension and handling is a fantastically complex science. It's an art form really - and a black art at that! Change one thing and it has a dozen knock-on effects. The single most important change I have done to my car's handling is to change the tyres. I'm now on my fourth set of different rubber and I can't praise them enough. The astonishingly brilliant Bridgestone SO-2 PPs. Best £500 I've spent.

Hoppy

Trout

iTrader: (1)

Hoppy,

and other UK drivers - AFAIK the Bump Steer removal may well have a significantly less dramatic effect on UK cars than it does on Stis (and P1s).

This is the word according to the PS guys - they say that typically there will be an improvement, just not as a dramatic as standard Jap cars are so far out!

I agree about the SO-2s tho, especially on 17in wheels which as a combination actually make the car ride better than SO-1s on 16in.

R

Hoppy

Rannoch, may I first apologise for the rather pompous sounding post I made above? It reads like I know something about steering and suspension! (I know how to set up a kart, but that's it!)

But yes, there may be something in what you say about UK cars. I should have asked more while Rich was doing my car (MY00). I kind of got the impression that the toe changes on my Scoob weren't as large as on some others. And I can't remember the figures it registered as they bounced it up and down! Must pay more attention.

Hoppy

NIGE K

Hoppy

Thanks for the info. I understand exactly what you a saying about making multiple changes and the knock on effect of these.
Karting does help
My previous before the scoob was an Integra Type R shod with Bridgestone S02's, which are the best tyres I have ever come across. Good to here that the same applies when they are on a scoob.
I dont expect to get the same sort of turn in on the P1 as the "R" but would like to improve it since compared to the "R" in every other way the P1 is outstanding.
It's cerainly a change getting back into a 4wd.
I reckon a day with Don Palmer wouldn't go amiss at the Mira Wet Handling Test Site.

Nige K