-nick

The 964 factory manual clearly shows the ball joint bolting up below the a-arm, with the caster eccentric head facing the ground.

Here is a pic from DC Automotive-


Then I come across this photo on Patrick Motorsports website which shows the ball joint mounted above the a-arm. This is on a 993, but it's the same in front as the 964 as far as I know-


Is there an advantage to flipping the a-arms over and swapping the left and right to mount the ball joint above the a-arm? Does it even matter?

Vandit

Wow, good catch. Never seen it done like that. It would be interesting to hear what folks like Bill Verburg and perelet say about this.

As far as swapping the arms, there's no need for that. Both arms are identical. You would have to flip the pressed bolt/stud on the arm tho. So I guess if you're already removing the arms, swapping them side-to-side would be easier than pressing the pin out and back in going the other way.

AOW162435

Every one of the dozens I've seen or worked on were mounted as per the diagram shown.



Andreas

sundog

Never mind.

ThomasC2

Mounted as in the picture, doesn't it make the upriight sit higher. Meaning that the tie rod comes even higher, meaning that bump steer gets even worse? Mounted as in the PET diagram must be better. Or?!

Thomas

Vandit

What governs the height of the upright and tie-rod is above the carrier since the strut/spring attach to the carrier not the arm. Doing this change would not affect the car's ride height, but given the same ride height, the change would benefit the geometry equivalent to running a slightly higher ride height.

Flipping the ball joint as pictured would have a roll center correcting effect equivalent to however much the difference in a-arm position is between the lower and upper ball joint installation configuration.

More technical discussion on the topic.
http://www.meganracing.com/tech/faqs...ct=Suspension:

ToSi

No, unless the attachment point to the upright is moved, i.e. ball joint up or down vs. wheel center, there will be no affect on RC or steering geometry. The arm can be shaped like a pretzel, the only thing that matters is the relative location of the pivots..

Angling the arm down like that might provide a bit more clearance to the tub just above the front bushing, protect the caster adjuster, or they just got them mixed up. Someone should ask Patrick, while the rest of us place our bets

Vandit

Think this through. Doing this change would do nothing to affect ride height, or clearance for the tub, or clearance for any sprung weight on the car.

Doing this change would reduce clearance for the brake scoops since they are mounted to the arm and the side of the arm closest to the wheel would be in a lower position.

Vandit

I just thought about this thread while looking at pics of my lower control arms removed from the car.

This alteration in suspension setup can be achieved without having to remove the pressed stud from the lower control arms. Instead, just swap the lower control arms between sides, and that in itself will put the pressed stud facing the opposite direction (upward) and allow you to run the ball joint in the above position.

EDIT: Just realized I said ^this^ in my first reply.

Vandit

I actually sent Patrick Motorsport a Facebook message and a link to this thread some time back, but I never heard back from them.


I still think it's a way to ever so slightly improve the car's roll center geometry and dial out bump steer when running at low low ride height.

dimma man

I emailed him yesterday and no answer yet.

kos11-12

maybe it puts the wishbone more parallel to the tie rod assembly so they move into a more or less the same arc of circle, therefore improve geo and bump steer (on compression & rebound)

ttAmerica RoadsterAWD

Maybe you get more Caster this way???

Porschenut_Lee

Bump. Anyone running this mod to further reduce bump steer? I'm getting ready to remove control arms for refurbish and might consider going this route.

Vandit

Contact this guy and ask.
http://emotionengineering.co

He setup Spyerx's car and put the ball joint above the control arm.