SDB

Hi All

I have reached a point where I have absolutely no doubt that Powerstation are the Daddies when it comes to setting up scooby suspension.

I had the opportunity to drive Jon Hughes' Car today at MIRA which was the third scooby I'd driven with the Powerstation Bump steer set-up.

Again, head and shoulders above any other Scoobies.

I am not saying I would recomend it to everybody because it makes the car a touch less forgiving. But if you are fed up with understeer and know what you're doing behind the wheel, I would have no hesitation in advising you to go or it.

(I should get one for free after all this publicity )

I have never been there myself but intend to make my first journey in my Type R to be in their direction. I understand they have a background in motorsport in a big way, and this shows in the set-up work they do.

I can't rave about it enough. It brings the real car out from under the layers of idiot proofing, etc. It makes the impreza the car it was born to be! (Must be in line for a free one after that comment )

Thank Jon...

Regards

Simon

BHORT

Simon,

I have been toying with the idea of going to powerstation since a thread on the driving techniques BBS about car setup some time ago. My concern is that there are several comments about eliminating bump steer making the car less forgiving especially for people such as myself who are only average drivers (always hoping to improve of course). What exactly in idiot terms are the changes that make the car less forgiving? I am going to do the wetter the better soon would it be best to go to powerstation before or after?

I would certainly like less understeer but not if my own abilities are going to be exposed! I certainly know my own limitations at the moment but would like 'better handling'

Brendan

Rich_R

Simon,

I envy your Sundays - what a hard life

How do they actually remove the bump steer? Are there any other changes they make apart from removing bump steer + adjusting camber and toe?

When you say less forgiving - in what way?

Cheers,
Rich.

JON HUGHES

Simon
Powerstation are the Daddies when it comes to most things with cars!!

When it comes to sliding an impreza around the wet handling track..we all know who the Daddie is

All you people worrying that you won't be able to control your car once the idiot proofing has been removed,fear not becuase I'm an idiot and I had great fun today

Thanks again simon/Don/Colin for a superb day!

Jon

Big Bear

I`ve had my car set up by Powerstation on the after talking to Moray and I have to admit they are very nice friendly people who do know there stuff . They also encourage you to see what they are doing so you can see where your money is being spent .
Rich to answer your quetion they shim out the steering rack by approx 5mm they also set the toe in ,the camber and made sure the rear was parrallel . They are well worth going to .
Hope this helps Dave

MorayMackenzie

Guys,

The powerstation bump steer removal is not simply a case of shimming the rack by a fixed amount. They put the car on their digital alignment system and find out through various measurements exactly how they need to adjust the steering gear to remove the bump-steer. Don't assume that the settings for one car, e.g. Dave/BigBear's will work for another, e.g, mine.

Moray

SDB

Hiya Chaps

In terms of what Powerstation are doing, I think it is important to be clear on something.

I had never heard of another company paying so much attecntion to bump steer for road cars. Everybody seems to be pretending (and some succeeding) to set-up your geometry for you, but the bump-steer thing just happens to be the thing I have latched onto in terms of the Powerstation set-up.

Beleive me I have spent considerable time finding REALLY GOOD places for geometry set-ups and these places are extremely hard to find (I would guess less than 10 in the country).

The thing I think we should recognise is that Powerstation came up with the idea. This means that it is just one part of their process for 'improving' your car's handling. There are undoubtedly countless other tiny ways they are superior to many other organisations, but they have one major thing we can all recognise as different (which is the bump steer thing).

What this means is that you can take you car to them and tell them exactly what you want in terms of an end result. They should then be able to use their experience and skills to produce that. I think they send you out for a test run for your comments / requests before they send you on your way (not sure).

Less Forgiving
--------------
Ok, this is not a simple thing to answer as it tackles the use of the words "better", "improved", etc. These are subjective words. One persons "Better" may be someone elses "Worse".

When a scooby leaves the factory it has been tuned to produce bump steer (the front wheels splay out (toe-out) when the suspension compresses. The reason for this is that when a Scoob is under heavy breaking the resulting weight difference between front and rear makes the back of the car very loose.

This is why lifting off the throttle mid-bend can cause HUGE oversteer and is probably the biggest cause of prangs in AWD cars.

The bump steer counteracts this by reducing the amount of sharp grip the front tyres can produce, thus reducing the difference in grip levels between front and rear. The draw-back of this is Understeer (This is why the prodrive settings advise toe-in - to counteract the bumpsteer).

The reason the car become slightly less forgiving is that this safety measure is removed. It basically means that the car does what you tell it.

So under heavy braking the car will be more tail happy (this is a good thing if you know what you're doing - this knowledge is only a 'Wetter the Better' course away ), but...

Mid bend is where the neutral bumpsteer set-up comes into its own.

Imaging this..
You are cornering right, fast.
The front left suspension is very compressed. The front right suspension is slightly compressed.
Ignoring the rear wheels.
In a standard car with front toe-in, the bump steer effect is forcing the heavily loaded front left into slight toe-out. The front right however is only slightly loaded so probably still exhibits a touch of toe-in. This cannot be good. This is the low level reason for the wooly feel to the front end when cornering.

With Neural Bump Steer, the front wheel are always pointing in the right direction, so you are going to get the most out of them at ALL times, not just the times when the geometry combined with the current bump-steer dictate it.

I love the Powerstation set-up, but I have learned that each driver has his own preferences and tollerance levels for every aspect of a cars handling. At the end of the day it is up to you.

BHORT
I would recomend getting the set-up before you go to "Wetter the Better" but just take care on the roads. Don't get me wrong, it does not make the car a viscious animal waiting to bite you on every bend, but it is a definate change to your handling, so care should always be taken.

Cheers

Simon

PS. I think I'm going to write an article on

Danny Fisher

I know this is a sad question to ask, but with this setup does the type wear become more of an issue?

An interested Dan

Trout

iTrader: (1)

Question - is the PS approach compatible with ALK? I have ALK fitted, am interested in the PS set up, but don't want to lose the additional benefits of the ALK (Ok I could fit Powerflex bushes, I know!).

R

rupertu

All very interesting chaps - except that in my book, bump steer is just that. The affect that hitting a bump mid-corner has on a car, by way of it's suspension. For example, what my STi did very badly, and what my UK cars have resisted very ably.

In my book, hard suspension is NOT what is required on the backroads of the UK

[This message has been edited by rupertu (edited 08-05-2000).]

SDB

Hi Rupert

You've missed the point mate.

The bump-steer removal does not change the stiffness of the suspension in any way.

Bump-steer is not a term to describe the affect on the car, it is a term to describe what happens to the geomtery of the car.

It is also not directly to do with Bumps in the road, but with the Bump of the suspension (ie oposite of rebound (bump/rebound)). This bump effect happens when the suspension compresses for ANY reason (not just hitting bumps).

In fact, I have no doubt that manufacturers would love to find a way of making bump steer unaffected by actual bumps in the road, and just be affected by load transfers.

Cheers

Simon

DavidG

Rannoch mentioned Powerflex bushes. What difference do they make to the handling? Would fitting them affect the warranty on a UK car?

Thanks,

David

MorayMackenzie

Sorry Rupert, as Simon Says... ( whoops ) you are indeed way off the mark. The bump steer being discussed here is the effect on wheel toe as the suspension moves through it's entire travel. After PS's work, the "bump" related toe in/out effect is reduced to practically nothing... yielding a much more neutral handling balance.

As standard, manufacturers tend to tune this characteristic to dull down the effect of an inexpirienced driver doing something silly mid corner... hence a general tendency for new cars to exhibit more understeer than oversteer.

Moray

MorayMackenzie

PS: Rupert... is "your book" available in softback yet?

[This message has been edited by MorayMackenzie (edited 08-05-2000).]

BHORT

Do any of the Powerstation changes affect the standard Subaru warranty?

Getting more tempted by the minute to have the changes made.

Brendan

Richard Simpson

My tuppences worth

I had teh PowerStation treatment a few weeks ago now and like most I cann't stop raving about it, like Simon said it now feels like I though the Scooby would in the first place.

I am definitely nothing special behind the wheel, average I guess and I have not found the car to be less forgiving. But then I do not drive to the limits of my car, although I am planning a trip to MIRA so we shall see.

In everyday driving it just feels so much sharper and responsive.

Get it done its worth it (IMHO)

Richard

NITO

Very interesting reading. I wonder how these changes are affected if you are using 215 tyres on 18" alloys. The wider the tyre the more exaggerated the bumpsteer and tramlining. I imagine these changes would reduce this too. Shimming out the rack sounds a bit dodgy to me but if it makes everything much better for all you guys then it must work. Does the turn in improve and the feel of the steering?

I too would like to know their phone number and location if poss..

Thanks,
Nito

Rich_R

Here you go...

(01242) 238400

BHORT

Powerstation are near Cheltenham, they have a website for a map, powerstation.org.uk. Perhaps we should ask for a BBS discount as it seems that they will get a lot of buisness from us.

Any comments from anyone about how these changes affect the warranty.
I was quoted £100 + VAT for the changes a couple of weeks ago for those people that are interested.

Brendan

dsmith

If this is bump steer then what is it when I'm driving my cart-like suspension MG Midget(Semi-Ellipitic leaf springs and Live axle at the back- don't even ask abou the front) and mid corner the back goes over a bump and jumps a few feet sideways (well it feels like a few feet...). Up until now I had thought this was 'bump steer'.

?

Dean

MorayMackenzie

dsmith,

That phenomenon isn't called bump-steer... it's called going too fast!

Sounds more like your "go-cart" suspension is so hard that it doesn't have the controlled travel and possibly roll it needs to keep the tyre in contact with the road... hence your sideways skipping action.

Moray

DavidRB

It's an issue of semantics (words). Bump & rebound are terms used to describe the compression and extension of the suspension components, specifically the spring/damper unit.

Bump steer is simply a deflection in the direction of a wheel (around the vertical axis) and primarily affects the front wheels.

As the suspension is compressed (primarily by cornering forces, but also possibly by bumps), the wheel is deflected slightly outwards. When turning, the effect on the outside front wheel is the same as if the driver slightly reduced the amount of steering lock being used. The end result is understeer.

It's a bit like describing dampers as "shock absorbers" or "shocks". Dampers don't really absorb the shocks at all, the springs do.

What you get with hard suspension is a "loss of steering over bumps", or more correctly, a loss of <I>grip</I> as the suspension is unable to absorb the sudden compression caused by the road and the wheel is pushed up into the air (although it doesn't have to actually leave the road for grip to be reduced).

It's the reason why racing cars set up for smooth racetracks get embarrassed by lesser cars with more appropriate suspension settings (i.e. softer) when out on bumpy, poorly surfaced public roads.

dsmith

I hasten to point out that it was cart-like in the sense of "Horse and ..." and not "Go-..."

Dean

NITO

Wouldn't double wishbone suspension get rid of bump steer altogether?? Why hasn't the scoob got double wishbone suspension, is it a matter of space?

rupertu

DSmith - thank-you, my point exactly, so what is the correct terminology for this phenomenen then oh patronising ones? I now know all this is only semantics DavidRB. Powerstation sound like the peeps though......

johnfelstead

Cars with double wishbone suspension also suffer from bump steer.

The best way to remove it is in the design of the car.

If you look at an F1 car for example, the steering arms run parallel with the wishbone angles, thia means that as the suspension moves up/down the angle between the steering arm and suspension wishbone and therefore upright stays constant.

On a production car, due to packaging/instalation constraints it is rarely possible to get this right on the production line.

There are various ways of fixing this, one is to move the rack position with packers. Another is to move the track rod end position on the front upright up or down, this second method is easier to use when using rose joints for the track rod ends.

Incedentily, bump steer ocures on the rear aswell, some cars use it on purpose, others have it due to poor design.

Finally (thank god you cheer) I did a project with ford utilising very acurate laser sensors to measure the rear geometry on the ford escort production line, based on the readings from the rear, the front toe was set to compensate for the amount the rear was out of true. The left and right toe settings were always diferent. The first trip for a re-track at kwick fit had the car incorectly set for even handleing.

DavidRB

rupertu: Didn't intend to be patronising, just trying to get all the information across.

I prefer it when people spell things out in simple terms, rather than type a couple of "aren't I clever" soundbites, it proves that they know what they're talking about.

Anyways, have we finally established what bump-steer is?

Shaun

Rich "The Butcher - Billy Joel look alike" Benton

rupertu

I didn't mean you DavidRB - but don't worry it's all cleared up now, I now know exactly what bump-steer is. I'm only surprised that I've never heard of the PS boys before, since I've had Imprezas for five years now.