alexjc4

Looks like we have an unusual level of consensus here!

Plenty of front camber
Max caster
~zero front toe


I talk about ride height effecting toe in static conditions of naturally it does translate to bumpsteer in dynamic ones.

So when we talk about (in most cases lowered) cars having static toe of 0deg we understand we will effectively have toe out with suspension compressed.

I remembered reading the importance in rear engine cars of differential tyre pressure front/rear to engineer slip angles that reduce oversteer condition. Which mean unusually high rear pressures.


I googled up this power point from michelin no less which has some specific points about 964 tyres on page 40/41 ( and an interesting bit about the benifits of stretched tyres on page 37)
http://www.google.co.uk/url?sa=t&sou...h6-trPZ7IbMOhA

kos11-12

Thanks Frank !

Alex,
This is interesting!
I run those pressure 30/34 cold for road, they go up to 32/36....took me a year to find out....

22 rear sway bar is planned, (TRG sale those)
I am also working on a outer tie road with a ball bearing, and spacers that could fit underneath the 64 arm, fitted with 993 inner tie road (not so convinced on the 993 RS wheel carrier) probably ready next year.....

meek

I thought that MY92> have a larger rear bar than the earlier C4s. Is this not the case? Will have to go and measure mine.

alexjc4

Rear ARB sizes:

18mm -90 C4
20mm 91- C2/4 Manual
21mm 90 C2 Manual
19mm C2 Tip
22mm T3.3 / TLook / T3.6
21mm TLook Tip
18mm RS

Mine came with the 18mm and I've swapped to a 21mm from the 90 C2

alexjc4

Sounds like a good bump steer solution, do you mean a spherical rose joint?


Interesting thread here on a drift forum I visit.
http://www.driftworks.com/forum/tech...dard-hubs.html

What do you not like about the 993 wheel carrier?

BTW I've read that the 993 RS and the standard 993 carrier have the same geometry.

kos11-12

C2 21 ...!?

Mine is 20 mm C4 1992 ( manufacture)

kos11-12

Interesting, well the bolt, spacers rose joint ...., all will fits underneath the 64 wheel carrier, but the straight adjuster do not fit ! I thought and have one made at an angle but the rose joint will eventually fail at the thread....
So decided to try and have made a one piece part CNC with a ball bearing pressed shaped at an angle (similar angle as the 64 original outer tie road)
I may need to make a few....

Porsche964FP

I run: H&R anti roll bars, front 26mm and rear 24mm. KWV3s. 8J and 10J.

Rear axle
Camber: Left -2º05' Right -2º07'
Cross Camber: +0º03'
Total Toe: +0º30'

Front axle
Castor: Left +3º00' Right +2º55'
Camber: Left & Right -0º24'
Cross Camber: -0º01
Total Toe: +0º24'

What do you gents think? Font toe and camber could be tweaked?

alexjc4

Interesting that you dont have any front camber. Are you sure it's 0.24 not 1.24? Not much caster either.

The main thing is; how does it feel? You might find the corner entry / turn in may be more perky with more caster and camber. Caster will move the wheel forward in the arch so you might need to watch for rubbing.

Porsche964FP

Yup definitely -0º24' hmmm looks like more camber at the front would be preferable! Castor, well it used to rub but then I angle grinded the mounting point between the bumper and wing as everyone does... which worked.

It feels great, but there is some bump steer. Whats the advantage of more caster? Is it simply that the wheel base is increased?

freedman

Other way round Frank

24 front, 26 rear

alexjc4

Caster is the angle of the steering axis. Think of the front forks of a bicycle, they lean backwards, thats caster. I gives self centering. It also gives a change in camber as the steering angle increases. If you look at the front wheels of a Mercedes on full lock you see it really clearly as traditionally they favour lots of caster. The geometry is a bit difficult to visualise but like with a bike it kind of makes your wheels lean into a corner.

Porsche964FP

Cheers,

Well it felt like the fronts were 26mm couldn't get them to damn fit - what a nightmare that was! Did you find it difficult?

Cheers Doc PS. Can you pm me your email again, would like to pick your brains!

freedman

My Indy put mine on, so no it was easy

kos11-12

I think more caster helps the wheels to self aligne straight quicker
I have 3,5 with no issues,
Some people mention between 4 to 4,5 (max)
Wonder what could be the right balance between front & rear toe & camber to improve the C4 handling,
Or should it just be like the C2 ....!?

Frank are those H&R bars work well ? ...
we all have more or less bump steer issues (toe out) when lowering the cars to RS or more.