ALFAGTV6.COM

[Tazio]

I have an Alfa 90 V6 which I have just finished and my mate has an Alfa 75 Twin Spark. We both have the same suspension and both suffer from turn in oversteer. This is however not on initial turn in but in the next phase of the turn. We have different wheels and tires (both offset and width) which does not seem to alter the problem.

Suspension:
27mm Pace Torsion Bars and matching rear springs
Koni Yellows fronts revalved (full soft rear halfway front)
Castor Rod Ball joints
Adjustable front Whitleine 27mm Sway bar (set to mid point)
Rear 24mm Whitleine sway bar
Urethane watts linkage, dedion bush and upper wishbones
one degree negative camber 3 degrees castor and zero toe.

Looking for sugestions as I feel it might be too large a rear sway bar combined with need for toe out.

Tazio

[Mats]

What about ride height? Front/Rear.
Cheap way to look for a cure is to raise it a bit in the rear and see what happens.

[Tazio]

Thanks for reply

Ride height is slight increasing rake front to rear of 10mm (measured on ends of sills) with about 130mm at the front chassis rail (ie below where lower wishbone bolts pass through).

Height is due to draconian road rule enforcement dictating 100mm clearance of lowest point of vehicle (engine down pipes).

[Duk]

Easy check, try disconnecting/removing 1 of the rear sway bar links.
When you say matching rear springs, are you saying their rate as increased proportionally to the increase in front spring rate?

[Tazio]

Sorry yes the rear springs come from Pace engineering as well and are sold as a matching set to front torsion bars.

Will try disconnecting sway bar links.

The other reson I thought the rear bar might be too stiff is we had to make up custom links as initially it broke the supplied links.

[Duk]

You could also try setting the front bar to it's stiffest setting.

[Giuliettaevo2]

set the castor to the max so you're upper controlarm just clears the shockabsorber.

[Mats]

Sorry yes the rear springs come from Pace engineering as well and are sold as a matching set to front torsion bars.

Matching on which car? Surely not on such an unusual car as the 90? Likely they are matched on a 75 V6 or GTV6.
Put some weight in the trunk and see what happens. You need to playu around and get an understanding for what gives a certain result in handling characteristics.

[Tazio]

Mats,

I agree.

"You need to playu around and get an understanding for what gives a certain result in handling characteristics"

On Wednesday I am going to start by disconnecting the rear bar and seeing if that removes the oversteer. Then start by fine tuning the adjusment existing on the car.
Front Bar and toe settings. Then create more if required, create rear bar end extensions or switch back to standard 22mm bar.

I was looking for a direction to start and you guys have given me one thanks.

[Tazio]

Thought I should provide an update on this.

I disconnected rear bar and it removed the oversteer.

So I set front bar to its stiffest setting but this made the whole front suspension a lot harsher but did balance the car out. So much so that in my favourite test bends I was able to vary between balanced/understeer/oversteer by playing with the throttle, before this would have ended badly.

I then disconnected both bars and found whole car to be different to drive in compliance of suspension.

Upon further investigation I have a large stiction issue with front sway bar urethane mounts due to angles and bushes and am in the process of converting to ball joint ones.

I also had a slight preload problem with the rear bar and so I am shamelessly copying Daniel's rear sway bar link set up (hope he does not mind too much) and having a slip on rear bar extender made by my cousin (sheet metal worker) equivalent of one hole extra in length so I can go softer there if needed.

It is very good to have it on the road and I may have a second gear problem! It is just too magical to rev it out all the way and with the tall gearing in a 90 it goes a long way.

[Duk]

Upon further investigation I have a large stiction issue with front sway bar urethane mounts due to angles and bushes and am in the process of converting to ball joint ones.

I also had a slight preload problem with the rear bar and so I am shamelessly copying Daniel's rear sway bar link set up (hope he does not mind too much) and having a slip on rear bar extender made by my cousin (sheet metal worker) equivalent of one hole extra in length so I can go softer there if needed.

Photo's?