Radical geometry reccomendations? - GC8 Impreza Turbo..

[Bradw]

Hi guys,

I am looking to ask your technical opinion on wether or not I should
attempt to set my geometry to mimic the hillcimb settings you have
previously published on your project car on the site.

I must stress that the car is primarily a 'daily driver' on UK roads.

I do a lot of fast road, drag and circuit work- now obviously no settings
can be ideal for all situations, but after lengthy discussion with a mate
of mine who hillclimb's a heavily modified TypeRA in the UK (named Graham
who has spoken to your tech team on several occasions regarding his
hillclimbing Impreza setup) I have decided I would like to try some slightly
more radical geometry settings.

Graham assures me with my spec there is a very good chance that the WL
'radical' settings would be close to ideal on my own vehicle and he has
found that day to day driving is not adversely affected by the radical
geometry.
He also drives to and from events in the race car.

Here is my own current suspension spec:
UK Impreza (GC8)
-----------------------------
Whiteline Anti lift kit
Whiteline Rear Fixed 22mm ARB - BSR20xz I think..
OE subaru front ARB
Whiteline Rear drop links
Whiteline Rear camber bolts

Front and rear upper strut brace
Lower front 4 point brace

KYB AGX 8 way dampers
Eibach pro kit springs:
F/lbs To be advised, eibach germany haven't got back to me yet
R/lbs To be advised, eibach germany haven't got back to me yet

MRT/Noltech front adjustable top mounts (street spec Urethane- not solid)

Tyres- Toyo Proxes T1-s
Treadwear:280
Traction:AA
Temp:A

ROAD
34psi front
32psi rear

TRACK
37psi front
35psi rear

DRAG
26 psi front
24 psi rear

So; these are the settings I found on the WL site that Graham has been
using to great effect in competition:

# Front alignment = camber -3:25, toe -2mm, caster +4.2
# Rear alignment = camber -2:5, toe -2.5

Am I likely to be seriously compromising tyre longevity and worse, safety
by employing such extreme geometry day to day??
Penny for your thoughts..

Many thanks!

(also emailed this to wayne directly)

Brad.

[jgevers]

Hi,

Although these settings are great for handling and grip you will wear the inside edges of both front and rear tyres quite a bit when you use them day to day.

Personally, I would use the camber settings but run toe in at +10 minutes for each wheel. This will 'calm' the car when driving straight but still have decent turn-in and front end grip. Tyre wearwill be a lot more acceptable. On the track it will start understeering a bit quicker though.

Regards,

Job

[Bradw]

thanks.

So you are recommending toe IN to be around 0.10' as opposed to -2.5'

or did you mean -2.4' ? :)

(just want to clarify)

thanks,
Brad

[jgevers]

Originally posted by Bradw
thanks.

So you are recommending toe IN to be around 0.10' as opposed to -2.5'

or did you mean -2.4' ? :)

(just want to clarify)

thanks,
Brad

I suggest running the camber as WL advises. The toe settings I would change to toe in +10 minutes each wheel instead of toe out. I realise the whiteline settings are in MM. Unfortuantely my John Bean 901 alignment machine is set on degrees and minutes for toe measurement.

regards,

Job

[Bradw]

argh

so they are in MM??? :eek:
I thought it was degrees/minutes :o

Anyone know how I can convert these to deg/mins then?
Thanks,
Brad


ie: # Front alignment = camber -3:25

'deg:min'?

toe -2mm

So mm then. ok

caster +4.2

deg:min or MM?

[Bradw]

Ok, sorted with a short phone call to Wayne..

Based on above spec and using Toyo road tyres:

F
Camber 1.5'
Caster MAX
Toe 0

R Camber 1.25'
Caster MAX
Toe 0

If I was to change to road legal slicks (and alter spring rate to be much stiffer)


F
Camber 2.5'
Caster MAX
Toe -1mm

R Camber 1.25' - Wayne you forgot to mention the rear camber on slicks! :)
Caster MAX
Toe -1mm


camber is in degrees of course ;)

Thanks to Wayne for making it clear quickly and simply :cool:

[Wayne]

Hello Brad,

As I had mentioned in our telephone conversation with road legal slicks I would recomend camber settings of approximately -2.5 to -3 degree's on the front and -2.25 to -2.5 degree's on the rear.
I would then set the toe at 0.0mm both front and rear, (I would not recomend these types of wheel alignment settings for every day driving).
You may get away with using your existing springs with the slicks, but would find it more advantageous to go for a stiffer spring rate as the tyre is going to provide far more grip loading up the spring a lot more than your current tyres are. If you were to increase the spring rates you will also need to look at increasing your shock absorber valving to suit your chosen spring rates.

The settings that we used on the vehicle in our article was using road legal semi-slick tyres along with 9kg/mm front springs and 8kg/mm rear springs.

I hope this helps you.
Cheers
Wayne
wayne@whiteline.com.au

[Bradw]

Originally posted by Wayne
Hello Brad,

As I had mentioned in our telephone conversation with road legal slicks I would recomend camber settings of approximately
-2.5 to -3 degree's on the front and -2.25 to -2.5 degree's on the rear.
I would then set the toe at 0.0mm both front and rear,
(I would not recomend these types of wheel alignment settings for every day driving).
You may get away with using your existing springs with the slicks, but would find it more advantageous to go for a stiffer spring rate as the tyre is going to provide far more grip loading up the spring a lot more than your current tyres are. If you were to increase the spring rates you will also need to look at increasing your shock absorber valving to suit your chosen spring rates.

Excellent.
Thanks Wayne.
As you can see I still posted the incorrect info on my second reply :rolleyes: - damn time difference
Was half asleep on the phone to you..

[Wayne]

Not a problem Brad.

If you have any further questions that I can help you out with, feel free, and I will do all that I can to help you out.

Cheers
Wayne