Thanks 5150fauxarri... but I'm a bit of a pack rat when it comes to spare parts. Once this project is done, I'll have 3 roadworthy Fieros to try to maintain!

Well, it's been a while since I posted an update here, but not because I haven't been working my buns off. For starters, as I began piecing the various front suspension component drawings together to create the complete front suspension illustrations, I realized that some pieces weren't fitting exactly right. But I rather expected this since there are so many hundreds of measurements that I was bound to make a mistake or two. Piecing the parts together is sort of like a sanity check... if things don't fit, then there's obviously an error.

For those of you who may be copying some of my drawings to your own computers, you'll want to revisit the four drawings of the front cross member on page 11. I updated the spacing between the lower control arm mounts and tweaked a few other related measurements. Also, I've replaced both ball joint drawings on this page as well since I had forgotten to include the range of movement in the side views.

As for new work, I've drawn up the tie rod recently. There was nothing noteworthy about this drawing (Edit: updated drawing to Version 2):



Now for the part that's taken me eons to get right... the full front suspension illustrations. Just for curiosity's sake, I've been tracking my hours on this build in an Excel spreadsheet since the beginning. (It'll make for some interesting conversation later once it's done, and possibly even help the appraiser determine some value for the time put in it). This next set of drawings has cost me 30 hours to date, and I'm still not finished. I'm posting the side view first as I continue to work on the other two views.

The difficulty so far has been trying to determine the correct angles of the control arms at ride height, and then drawing them at these angles. The earlier 3-view drawings I made of the arms were created at angles that suited the ease of drawing them, not as it turns out, at the actual angles they sit at when the car is at ride height. Here is where having done these in a CAD program would've made things exponentially easier. I can tell you right now that the jounce and rebound drawings later on are going to be stick figures, not illustrations like I did for the rear suspension! (Edit: updated drawing to Version 2)



Anyways, the noteworthy aspects of this side view drawing are that:

1. the tire dimensions were taken from the average between four actual stock-sized, new front tires (P205/60/15) at 32 psi installed on two different '88 GT's, so that's how the rolling circumference was determined;

2. the lower control arm angle was determined by a measurement specified in the '88 service manual on page 3-16. It states that the difference in height between the lower corner of the lower ball joint and the frame rail directly inboard of the joint should be 6.9 mm. Having done this, the upper flat surface of the lower control arm sat at an angle of 7.5 degrees pitched downward towards ball joint end;

3. once the lower control arm was drawn correctly, the knuckle was added after being tilted for 5 degrees of caster; and

4. finally the upper control arm angles could be determined, and the upper arm drawn accordingly.

This side view will be used later on to determine what percentage of anti-dive is built in to the stock '88 suspension. Those of you who are more wiley and ambitious can already figure out this value from the info I've posted here and earlier.

[This message has been edited by Bloozberry (edited 11-19-2011).]

Thanks 17Car for the comments. I wanted the source drawings to be accessible and modifiable by as many people as possible, even those without CAD software, so I chose the very common drawing software tool that comes with the basic the Microsoft Office Suite. I use Microsoft Excel as the backdrop for the images after having forced the gridlines to squares. The resulting image is a vector drawing (scalable), but is essentially a line drawing that isn't renderable into 3D. That's the drawback to making it available to everyone. I haven't yet posted the source files since I continue to find small errors as I piece the components together. Once I feel they're at a stage where they are as good as I am am prepared to draw them, I will look for a site to host the files for anyone to download.

Now on to a few corrections to earlier drawings For those of you following this thread and downloading the drawings, you'll want to update your files with new pictures of the tie rod above, to which I've added the degrees of motion to the side view (you'll note that it's annotated Version 2). Also, I noticed several errors in the original drawing above titled 1988 Fiero Front Suspension LH Side View so I corrected them and annotated it Version 2 as well. The errors consisted of miscalculated front cradle mounting height and the ground clearance to the bottom of the cradle. As well, I noticed that I hadn't completely drawn the lower profile of the lower control arm which further reduces the overall ground clearance. If I discover any other errors I'll just keep changing the Version number and call attention to the changes in future posts. Likewise, if anyone sees any errors, please do not hesistate to let me know so I can correct them.

Finally a new drawing to add to the collection: the rear view of the front suspension (Edit: updated to version 2 - corrected location of outer tie rod end):



There are a few noteworthy details in this drawing:

1. The '88 front track width (59.7" or 1516.5 mm) was taken from an article in Road & Track (Oct '87). I've found the track width reported in several magazines and books to be erroneously listed as 57.8" including Gary Witzenburg's Fiero, Pontiac's Potent Mid-Engine Sports Car;

2. The camber is set to zero degrees in accordance with the alignment specs.

3. The kingpin angle is 6.0 degrees according to Gary Witzenburg's Fiero, Pontiac's Potent Mid-Engine Sports Car;

4. Neither the upper nor lower A arms are horizontal as viewed from the rear (or front) at ride height. The upper A arm is angled at 6.2 degrees upwards, and the lower A arm is angled at 7.5 degrees downward as measured from the top surface;

5. The scrub radius is an unverified 40 mm as I was unable to find any referenced documentation identifying the actual measurement. It's interesting that it's as large as it is despite the front wheels on the '88 being only 6" wide and having a relatively large 37mm offset;

6. As reported earlier, the center of gravity sits at 19.5" above the ground according to Road & Track (Sept 1983). Admittedly this is for the four cylinder cars, but I am assuming the CofG height most likely did not change significantly with the V6. It's longitudinal location did though;

7. The outer tie rod end is situated about 15mm outboard of the plane defined by the upper and lower ball joints. This results in built-in understeer as the roll angle increases. For there to be no effect, all three would have to align in the same plane; and

8. The shock absorber and the sway bar were left out to simplify the drawing

I think that's all that's pertinent about this drawing for now. Next up is the top view, and then on to some basic geometry analysis.

[This message has been edited by Bloozberry (edited 11-19-2011).]

Thanks JFrost for the kind words.

For Yellow87FieroGT: Yes... the front track on the '84-'87's is 57.8 and the rear track is a bit wider at 58.7 according to many different magazine sources.

Edit for speeling

[This message has been edited by Bloozberry (edited 11-18-2011).]

A quick note for those of you saving copies of my drawings: I made an amendment to the drawing above entitled 1988 Fiero Front Suspension Rear View. The latest version (V2) above has the outer tie rod end raised about 5mm higher than Version 1. The reason is because I realized I had not rotated the knuckle to match the built in castor in this view which placed the steering arm on the knuckle lower than it should have been.

Now for the last of the layout drawings, here is the '88 front suspension assembly as viewed from the top:



There aren't many noteworthy aspects to this view except:

1. the difference in control arm lengths is quite apparent;

2. other than a symbolic rack, I didn't include the steering rack and pinion assembly... just too much work for no added value;

3. in the notes, I forgot to mention I left out the sway bar. I'll correct that only if other changes become necessary.

Everything in these three last drawings can pretty much be summed up with the values I've tabulated in the chart below under the heading "Coordinates". The "Static Data" portion of the table contains some measured and some calculated data. All the static data points are directly measured except for the roll center, swing arm length, and anti-dive, which are calculated. I go into how these are calculated in a later post. (Edit: updated chart added).



With the right formulas, this data is all that's needed to calculate the change in caster, camber, tire scrub, toe, front swing arm and side swing arms for any given amount of jounce, rebound, or roll. I know all of this because Herb Adams book tells me so. Too bad Herb doesn't get into the detailed formulas, referring instead to a computer program he uses... great help

[This message has been edited by Bloozberry (edited 12-08-2011).]

[This message has been edited by Zac88GT (edited 11-25-2011).]

As with the front suspension coordinates, I've tabulated the rear suspension coordinates in the same format for anyone to use.



Once again, given the coodinates in the first part of the table, the swing arm, rear roll center height, and anti-squat can be calculated as I've shown on page 9 of this thread for the rear end.

(edited to add updated table)

[This message has been edited by Bloozberry (edited 12-08-2011).]