Ragos Elias

I just fitted today the ALK and tommorow I will go for geometry setting.
I was running with light prodrive suggestion
(camper 0,5 neg, front and 1mm toe in all over).
The ride was better than the standard settings ( reduced understeer and better cornering) and now with the ALK ( 0,5 deg pos.caster)I wonder what setting should I go for.
By changing the rear anti roll bar with bigger one 22mm (20 mm before)from scoobymania the rear is more solid than before.
Your help will be apreciated.

Elias

MorayMackenzie

I think MRT recommend settings for the ALK... I seem to remember (I hope I'm wrong) that they recommend setting a bit of toe out on the rear! So, MRT may like shopping trolley handling!

psyg

Sometime ago I got this mail, maybe it helps a bit:


From: Whiteline Sales <sales@whiteline.com.au>
To: Whiteline-egroups <whiteline@egroups.com>; WRX-egroups <wrx@egroups.com>
Sent: vrijdag 12 november 1999 1:22
Subject: [wrx] To toe or not to toe - Whiteline

Some argue 1-2mm toe in gives the best response etc., others argue toe out for the rear is the way to go. This almost leads me to believe that 0 toe would be best...

Allowing for language translation, response is not the correct word here. Toe-in can not deliver improved response or turn-in either front or rear.

Given the fact that the Scoob is a 4wd rear toe setting can be important too, though I know one setting is always a compromise for various conditions. Answering the following questions could help me in my decision:

The more relevant question is one of stability vs instability, front vs rear. Discussed more later.

What's the reaction of the Scoob when accelerating? Lifting the wheels leading to toe in?

Both front and rear will tend to toe-in marginally under acceleration (torque application), the front more so than the rear. Although fitting the anti-lift kit will also reduce this. The body lift component of accelerative forces will have minimal effect on toe change, albeit towards toe-in.

Friction (resulting from grip under way) will however force some toe-out which is cancelled by drive torque with the net result being close to neutral. ( In a front wheel drive or front wheel drive based all wheel
drive like the WRX)

How doe toe react when acceleration out of a corner?

There are 2 separate forces involved here. With respect to acceleration, refer above.
As for the consequences resulting from roll, rear change is almost immeasurable.
Front change (bump steer by another name) is also negligible. In fact you've got us here as we have never measured it precisely as it is not an issue with the WRX. A precise value would therefore be academic though easily obtainable with a contemporary wheel aligner. Please let me know your vehicles "bump steer" value if you get this done. Meanwhile, we will also check this at our end.

What does toe do for tuning in?

Historically, static toe-in was used to pre-empt dynamic toe out or to deliver a certain "numbness" to the steering, hence the opposite to response. It does also deliver stability at cruise. Toe neutral is a natural state, where as toe-out is an unstable state. This can be harnessed to deliver exaggerated steering or directional change response to either front or rear. Whiteline recommend marginal toe-out on rear to
allow the rear to respond quickly to directional change at the front.

What reaction gives the toe setting when under breaking?
The opposite to acceleration.
Isn't zero toe best for straight-line stability?

Negative scrub radius geometry (only really relevant to front unless Cray computer modelling is your pass time) of WRX leads to toe-out off acceleration or when cruising with low torque. Which type of straight-line stability are we talking about here?

Removing torque from the equation, there is now doubt that toe-in delivers more straight line stability during steady cruise however at the expense of turn-in response. That is why race teams will change the toe values depending on track and race distance. A tight track will see higher values of toe (both in or out depending on driver preference), while endurance races on relatively fast open tracks will see smaller values.

You can conclude from this that you can either promote stability/instability at the front or the rear using toe to deliver a desired result. We can also conclude that in contemporary steering and chassis design, bump steer effect is negligible and only serves to confuse the argument.

I know we have probably given more information here than you wanted, but even this only scratches the surface of the available information and variables that need to be considered. Most importantly, I can not stress enough the fact that alignment settings are NOT an "absolute truth" that can be held up as a undisputed rule. It is a dynamic process that will vary from driver to driver, car to car not to mention the driving environment.

Whiteline has no agenda in publishing it's alignment settings or recommendations as part of its's suspension packages. It is not copyright property that we profit from, it is done to help people get the most out
of our products and their cars. These settings are the result of a lot of time and effort on our behalf and represent an optimum starting point for enthusiastic driving though we strongly encourage people to then monitor tyre wear and balance to fine tune the absolute numbers for individual circumstances.


Bottom line, just follow our recommendations to start with and fine tune later. It won't cost you a cent and it will save you a lot of initial headaches. You've got nothing to loose.

Good luck

Jim Gurieff
Whiteline Automotive