PhilBennett

Hi Simon - :-)

I can see what you are saying but you are still too focused on the "hard on the brakes, turn in" senario.

I was just surprised that increasing front toe in made the car feel better in the initial part of the corner - as it will start to promote corner entry understeer.

This is my interpretation of the Prodrive set-up.

The front toe in is there to reduce the feel of the front bump steer in bump - as I am imagining the front of the car has toe out in bump.

Once the car has taken set - it is the rear toe in that improves the car at the exit, as it helps to contain oversteer under power.

The increased negative camber will simply assist in giving an overall increase in corner stability and grip.

For sure the wild reactions are at the extremes of toe in and toe out; and as you say the only way to get a good set-up is to test. If you feel that the set-up is good then it is good.

Simon, We should do some test work and market our own handling kit!!

Richard Simpson

Well now I am utterly confused.

I have booked in at Power Station in Cheltenham on Saturday for a geometry check and adjustment. When exquiring I was told that it will take about one hour for the geometry check plus another hour if the bump steer is adjusted/removed.

Question:- what should I expect from removal of the Bump Steer?

Will it become somewhat *tricky* or just sharper?

PhilBennett

Question:- what should I expect from removal of the Bump Steer?

Will it become somewhat *tricky* or just sharper?

Hi Richard - Basically it will become more stable under braking and over crests.

A vehicle can have bump steer at the front and rear in both bump (compression) and rebound (extension).

I haven't tested an Impreza and don't know what the values are.

Neil F

This is all too much for me and I am now bowing out of this thread for good. I would love to understand all this fully but I now feel I need to experience far more driving situations and spend hundreds of pounds having my steering geometry adjusted to various settings in order to sample the plethora of handling differences you guys all mention.
The only thing I have to offer by way of correction to Mr de Banke is that "Ackerman" should be spelt with a capital 'a' as it is named after a Mr Ackerman who designed the dual radius steering mechanism.
He also got to number 3 with Stranger by the Shore which he played on a pink oboe.

Neil.

Pete Croney

Simon and Phil

You are both right... and all is apparent if you consider what is happening to the car's suspension.

Toe out will improve turn in, BUT not on an Impreza, because of the loads applied on the suspension location points.

The drag generated by applying slip angles (we'll call it turning in)will swing the wheel backwards, so increasing toe out. In a rose jointed race car, this doesn't happen.

On a Scoob, by applying some toe in, we are reducing the amount of toe out that will occur under load and therein increasing the car's stability.

For the record, I run 2deg 15mins negative with 10mins of toe in, front, and 1deg 30 mins negative set parallel rear. I too have done lots of testing and this set suits my driving best.

At the end of the day, it is about what suits the driver. Some people are very late on the brakes, turning in under heavy braking and they need a car set up which others would find understeers. Other drivers get most if not all of the braking done before turning in and can use a set up which would have our first driver facing the wrong way all the time.

SDB

Stable is not necessarily the best description.

The bump steer is put there to make the car less like to oversteer under braking / lift off...

When you take it away the car feels really tight and accurate at the front. Lots of turn-in bite followed by lots of mid bend bite... At the Front Though...

This means that the car may be more challenging to drive on the limit if you don't know what you're doing. If you DO however, the car is FAR more driveable.

I LOVE the set-up Powerstation do and will definitely have it done to my scoob when I pick it up.

Regards

Simon

Richard Simpson

I had the Power Station treatment for my geometry yesterday, wow it is just fantastic. It wasn't too far out before, but had a fair amount of bumpsteer.

Afterwards.... varstly better turn in and more responsive. It now handles like I thought a Subaru would.

If you are in the area it is definitely worth a visit

stuartl

Would the above also apply to a P1?

JON HUGHES

I also had my car set up at powerstation last week,my settings were not far from the prodrive ones but the removal of the bumpsteer has made a great improvement

I'm at MIRA next sunday,so if what Mr De Bank has been saying is true I should be in for some fun...
Jon

[This message has been edited by JON HUGHES (edited 01-05-2000).]