suspension engineering.

[Emc209i]

The Elise has a 2000lb curb weight though. Would a setup like that support an additional 1000 lbs? Wouldn't the rear toe control link allow some amount of bump steer of the heavy rear end? That was the problem with the pre-88 setup wasn't it?

[Series8217]

The Elise has a 2000lb curb weight though. Would a setup like that support an additional 1000 lbs? Wouldn't the rear toe control link allow some amount of bump steer of the heavy rear end? That was the problem with the pre-88 setup wasn't it?

I don't see any elements of the design itself that would prevent it from being used on a heavier car.

The Elise has ~1250 lbs over the rear axle, and the Fiero has ~1600. We're not talking orders of magnitude here..

[Emc209i]

What about bump steer?

[ericjon262]

What about bump steer?

C6 vette uses a toe link without crazy bumpsteer problems... the problem isn't the link, it's the placement.

[The Dark Side of Will]

What about bump steer?

The inner pivot of the toe link shares a bolt with the inner pivot of the lower control arm.
It looks like the outer pivot of the toe link is the same elevation as the lower ball joint, and the length of the toe link is the same as that of the lower A-arm.

IOW, the toe link is "in-plane" with the lower A-arm under all circumstances. There should not be any bump steer.

[The Dark Side of Will]

I don't see any elements of the design itself that would prevent it from being used on a heavier car.

The Elise knuckle is not very tall. Shorter knuckles make it easier to achieve camber gain; taller knuckles reduce (upper) control arm loads.

That's just something to consider in the design. The Elise hardware is TINY.
Obviously a design like that could be built for the Fiero, with appropriate design considerations.

[Series8217]

Obviously a design like that could be built for the Fiero, with appropriate design considerations.

Yup.

[The Dark Side of Will]

In doing something from scratch and I decided on control arms instead of a 5 link, I'd look at something more like the Ferrari 308 H-arm pair I linked earlier.

[ericjon262]

well, I think I am going to go with a double "a" arm design. Yesterday, I picked up a set of C5 knuckles, complete with bearings, wheel speed sensors, parking brake drums, and halfshafts.

[The Dark Side of Will]

The acquisition department making engineering decisions... You're assimilating well into the Navy

[ericjon262]

The acquisition department making engineering decisions... You're assimilating well into the Navy

lol, I got a good deal on them, main thing I wanted was the parking brake setup, I'm not dead set on anything yet, but a double A arm should outperform anything I have currently, and is fairly simple

Edit:

Do you feel like the C5 knuckles are a bad idea?

Edit(again): FWIW, it looks as though 98+ Firebird dual piston front calipers will bolt onto the C5 rear knuckles...

[The Dark Side of Will]

The acquisition department making engineering decisions... You're assimilating well into the Navy

Do you feel like the C5 knuckles are a bad idea?

Edit(again): FWIW, it looks as though 98+ Firebird dual piston front calipers will bolt onto the C5 rear knuckles...

FYI, the '98 F-body and C5 Corvette front calipers are dimensionally identical. The only difference aside from the "Corvette" lettering is that the 'Vette units are pressure cast vice gravity case and slightly stronger.

C5 knuckles aren't a bad idea... But you have to design the suspension around them. They're quite tall compared to the Fiero knuckles. For a tall knuckle to have good camber gain, the upper ball joint has to move inward a good bit through the suspension travel. This is difficult when using short control arms, as you may be forced to do when using those knuckles in a Fiero.

The Vette has extremely high offset wheels, which allowed the engineers to push the knuckles further out and end up with longer control arms.

//

I had been thinking for a while that to fix the '84-'87 car's wheel hop and pro-squat, I'd have to equalize the height of the forward and rear pivots of the rear control arms. As delivered, the forward pivot is LOWER than the rear pivot, resulting in pro-squat and wheel hop.
I can't raise the forward pivot because the transmission is right over it.
I'd been thinking that I would end up lowering the rear pivot, but that hurts the camber gain and roll center geometry.

I had also been thinking that I should swap over the 2nd Gen W-body (or N-body or some other modern platform) aluminum knuckles. The steering arm mount on these knuckles is lower... low enough that I could use a bump steer adjustment stud to put the toe link in plane with the control arm and eliminate bump steer.

Combining the two ideas... i realized I just need to built a lower arm that reaches forward of the transmission to raise the forward pivot and re-use (or raise) the rear pivot. The toe link would share a pivot bolt with the rear control arm pivot, so reducing bump steer should end up pretty easy.

[Series8217]

C5 knuckles aren't a bad idea... But you have to design the suspension around them. They're quite tall compared to the Fiero knuckles. For a tall knuckle to have good camber gain, the upper ball joint has to move inward a good bit through the suspension travel. This is difficult when using short control arms, as you may be forced to do when using those knuckles in a Fiero.

Wouldn't shorter upper control arms make it easier to have good camber gain with tall knuckles, since the upper ball joint moves in further for the same suspension travel as a long arm?

[The Dark Side of Will]

For the same camber gain, the ball joint has to move further inboard than with a shorter knuckle. Given a constraint on arm length (frame rail and track width) it's harder to get the camber gain on a taller knuckle.