Real tech discussion on design, fabrication, testing, development of custom or adapted parts for Pontiac Fieros. Not questions about the power a CAI will give.
After skimming through several threads written in word salad about rear bump steer, I am trying to clarify the problem and a solution. Is the bump steer issue that the tie rods and lower control arms are of unequal lengths, and due to this the toe moves slightly as the suspension travels away from the center of its range?
If so, this looks like an easy fix as shown in these two pics:
The knuckles have been swapped with each other to swap the sides that the tie rods connect to the engine cradle. This allows for easier placement of the connection point of the tie rods to the engine cradle.
This drawing keeps the knuckles in their original positions, but changes the location that the tie rod connects to the engine cradle. It shortens the length of the tie rods to match the radius/length of the lower control arms.
I can't speak to the particulars, of the change, but I can speak to the fitment. and this won't work on my car, and I suspect several others as well, as the inner mount occupies the same space as the transmission case on the driver's side.
"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
The solution shown in the picture only works for the passenger side only if it clears the crank pulley.
The solution in the drawing looks like an easy fix to move the weldments for the tie rods closer to the knuckles. So easy that I wonder why Pontiac did not just do so. I'm wondering why they didn't. Then again I'm seeing all sorts of odd mashups from the factory designed during a time when CAD was in its infancy and fuel economy had become a big concern.
The pivot axis for the control arm is NOT parallel to the centerline of the car. The forward pivots for the control arms are further apart than the rear pivots. You can see that from your Stock vs Proposed top view above. The original toe link isn't awful... it just isn't great.
It does mount the toe link in single shear, but since the ball joint is taking all the lateral loads, that should be ok.
I'm actually expecting to use that setup with my fabbed hub carriers, but I'll use a spacer so I don't have to cut into the cradle that way.
If I go this route I'll probably cast and then machine.
I want to see how bad it is after all Delrin bushings, coil overs, larged dia rims and lower profile tires. It would be part of stage 2 next year for this car.
CaptainHindsight wrote: ↑Thu Aug 26, 2021 5:28 pm
If I go this route I'll probably cast and then machine.
I want to see how bad it is after all Delrin bushings, coil overs, larged dia rims and lower profile tires. It would be part of stage 2 next year for this car.
whats your casting method? what are you doing for material QC? this could get tricky for parts under the amount of load that a knuckle sees.
"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
I'm very familiar with the process, but how are you going to verify filing without voids/porosity? where are you acquiring material and how are you ensuring it will meat structural requirements? I'm definitely not saying don't do it, but this isn't a part you want to break going down the road.
"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
10-4, that makes this seem like a much more reasonable undertaking now. I was envisioning my backyard setup and cringing.
"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
The rear 84-87 cradle and suspension is really bad. You should look into transplanting an '88 cradle and suspension. Especially if this is your daily.
ericjon262 wrote: ↑Thu Aug 26, 2021 10:28 pm
10-4, that makes this seem like a much more reasonable undertaking now. I was envisioning my backyard setup and cringing.
That little cauldron in your back yard flashed as a mental imagine for me too. Haha. Man that was a long time ago.
he rear 84-87 cradle and suspension is really bad.
What is so really bad about it? The toe changes slightly near the end if its suspension travel with the factory bushings and tie rod mounting locations.
I can argue that whole car is an under powered and twisty and needs a proper frame, wheels, tires and drive train.
Everything. It's a FWD cradle flipped 180* and mounted backwards. It was never designed to be in the back of a car, much less a sports car. The difference between the older suspension and the newer is night and day. My little brother used to own an 86 GT that had a lot of stuff done to the cradle including solid bushings. When I would drive his car after driving mine it felt like a minivan.
You don't have to, entirely your decision. And I'm sure at this point in time finding an 88 for part out would be very difficult. But you can spend a ton of money and time on the older suspension and it won't be as good as the newer stuff right out of the box. There's a Fiero 3 feet from me that's got a cradle swap in it. I would have been mad if I didn't know any better and had tried upgrading the original cradle first. Just sayin'.
