Jimbo1367

It’s got to be hard to do anything in the garage with temps that high. Yet you still do. Thanks for giving us threads

fieroguru

iTrader: (1)

Yeah, yesterday was a hot one, but at least I wasn't doing any welding!

fieroguru

iTrader: (1)

I didn't spend much time in the garage today, just long enough to cut open upper and lower ball joints and inner/outer tie rods to get precise pivot details. Also detailed out the outer tie rod and upper ball joint. SOme work creating blocks of the geometry and started playing around with the stock setup.

The stock 88 front suspension is pretty good overall - especially at stock ride height. If I can get my custom knuckle/Gen 4 rack setup to be close to the stock 88, I would be very happy.

Stock Geometry with 0.7 degrees of static negative camber:


With 3 Degrees of Roll:


With 1.5" of bump:


Things get worse when you lower the front of an 88 1 1/2" with lowering springs (my current setup). Here is a stock suspension lowered 1.5 inches with lowering springs:
CG is lowered 1.5" and distance between the CG changes to 15.78" from 15.85" so no significant change in roll resistance, because the roll center dropped about as much as the CG changed.


Notice improved camber gain, but at the expense of the roll center moving 2.35" laterally.


Definitely more bump induced toe change.


Most 88 Fieros running autocross or track days with a stock based suspension that have been lowered, are running a geometry setup like above, or worse (geometry gets worse as you lower it further). It works, but definitely not ideal.

Here is the current geometry for the modified knuckle.
The CG was lowered 1.5" and the RC was raised, so the distance between the two becomes 13.64 vs. 15.85 or a 14% increase in the resistance to roll.


With 3 degrees of roll, the loaded wheel still has a smidge of negative camber, the unloaded wheel has just over 2 degrees positive camber and the roll center only shifted 0.394" vs. 2.35" with lowering springs.


Toe change with bump is slightly better than stock with compression, worse than stock with rebound. I still have some options to refine outboard tie rod height, lateral position of inner tie rod pivot, as well as changing the elevation of the rack position.


Getting really close to starting the fabrication process for the knuckles...

Michael Yount

iTrader: (1)

Actual design. What a concept.

Nice work guru.....

JoshHefnerX

What suspension software is that?

fieroguru

iTrader: (1)

I am doing all the drawing as well as suspension layout in AutoCAD. I am not using a suspension analyzer software
This means I have to move/rotate the blocks, realign the pivots based on the arcs of the control arms/tie rod and draw the intersection lines and dimension... I probably have about 8 hrs in laying out the 9 drawings above.

fieroguru

iTrader: (1)

Started to fabricate the knuckles...




Added the bracket for the brembo.




Working on the side plates to enclose the gap between the inboard and outboard plates

fieroguru

iTrader: (1)

Knuckle is about 80% welded... starting to look like something.







Right now it is about 6 oz heavier than the stock 88 front knuckle, which is 5 lbs 2 oz. The finished knuckle will be 1-2 lbs heavier than stock, which I am OK with.

JoshHefnerX

You got a jig or something to help w/ warping?

pdxmotorhead

Have you ever compared your uprights/Knuckles with a Spec Racer Ford?
They use the same ones front and rear, if your out at a track hunt one down,
your design would work in well with the AWD potential. Mostly look at how they use
the same bearing assemblies for both front and rear assembly.

Great fun to watch..

Michael Yount

iTrader: (1)

Is Spec Racer Ford the current iteration of the old Sports Renault/Spec Racer class? You can tell how long it's been since I raced in SCCA..... I used to buy the "hot shoes" 1-race old tires for use on my ITC Corolla. I used the same 185/60 front, 205/60 rear tires on my car. Dirt cheap they still had plenty of life in them.

fieroguru

iTrader: (1)

I welded the bend slots first as I knew they would pull a bit, but I was able to bend back to where they needed to be. After that I assembled the inboard and out board plates and the 5 internal sleeves, bolted tightly to a wheel bearing and installed a ball joint ear brace that kept the upper and lower ball joint ends parallel. Welded all the internal sleeves which really locked the parts together, then made the filler plates and tacked them about every 1". Once the tacks were done, I fully welded the perimeter. Overall these efforts kept any welding distortion to a minimum. Based on what I saw with the first one, I will do the same on #2.

I hadn't until you posted about them. They are somewhat similar to the stock 84-87 rear knuckle (strut based with tie rod. I had played around with adapting an aluminum W-body knuckles front/rear before going down the custom knuckle route. Lots of options, but not sure any method is easier or less work. At least with the custom knuckle, I can design the knuckle assemblies to specifically work together with the fewest # of additional parts.

pdxmotorhead

I was thinking parts availability for the "less fab oriented" folks.. For a AWD it would be interesting/// There is also the ability to use pretty generic bearings and such.. Most just going... What if .. oh crud do not need another project...

fieroguru

iTrader: (1)

Lots of cutting welding and grinding but the other side is about 80% build and the original side now has the tie rod arm complete. I think it took longer to make the fxiture plates to locate the tie rod boss and add the upper and lower plates than it took to make the other knuckle... things always go faster the 2nd time and once you have all the needed tools figured out.

I still need to ream/taper the holes and fit the ball joints/tie rod to the proper installed depth, but maybe one more weekend and the front knuckles will be done. Then I get to move onto crossmember and a-arm mods.

Jimbo1367

I would measure the OD of the tierod arm and right it down with exactly where u measured it from. Use it for a reference to see if it ever flexes. Just a thought

jim

AAIIIC

iTrader: (19)

What is the source of the Brembo calipers, or are you intentionally leaving that unspecified for now while you work out the details?

fieroguru

iTrader: (1)

I am intentionally keeping that information unspecified. When the time comes, it will be shared with appropriate parties.

AspenW41

Sir,
I am thinking about doing the same thing to a 88 formula. My main question is Were you able to install a cataylic converter on your exhaust setup? I live in Maryland, which is a grandson of California's emmision program. So I am trying to keep any possibly of emmission failure when getting the car tested. As a former emission inspector, I am sure the car's new emmission standard would be the donor car, say a 05 Pontiac GXP.

G Atsma

If you really were an emission inspector, you would know for sure how to spell EMISSION. One "M", two "S"
And I don't think Fieroguru put any cats on his car. Read back thru the thread. I think it shows somewhere.

AspenW41

Thanks. It was 3am in the morning when I was writting this out. Yes, I was doing the half of the Inspections in Aspen, Colorado in the 90s. Sorry for the mistake...