Thanks doublec4! But given the drastic measures needed for the rear of this thing, the jury is still out whether the rear suspension is going to be any better than stock.

Stage 3A - 149 MM Cradle Ground Clearance & 24 MM Fender Mod

Well, with 130 mm gap still left between the top of the tire and the fender, it's apparent that a combination of spring drop and fender mods are going to be needed to get a decent looking car out of this. Rather than make two separate stages, one with a spring drop and the other with a fender mod, I decided to analyze two different spring drops in separate stages combined with fiberglass fender mods in both. The first is this one where I lower the car 30 mm and reshape the rear fender by lowering the edge 1" as Don suggested. This combination results in a 5.9" (149mm) ground clearance with the cradle, and decreases the fender gap to 76 mm (3.0") which is still a bit too much for my liking, but it is worth looking at in depth to weigh the pros and cons of appearance vs performance between this stage and the next.

So here is the drawing for now, the Lotus Suspension Analyzer results will follow after the schematics of both stage 3A and 3B, as long as Zac88GT is still out there. :crosses fingers:



In a rather roundabout way, I achieved the 30 mm drop in the chassis by modifing lower strut adapters. This new design drops the entire chassis by 50mm but when combined with a lengthening of the coilovers by 30 mm, the resultant chassis drop is 30mm. You'd think this would result in a 20mm chassis drop, but the angle of the strut comes into play.

One of the more significant impacts resulting from the redesigned lower strut adapter is the regaining of available jounce travel before the strut bottoms out. During the earlier first stage when the cradle was into the chassis, that used up some of the jounce travel at that time. A further shortening of the springs in this stage without the modified lower strut adapters would have reduced the spring travel in jounce to an unacceptable 50 mm (2"). I took advantage of the space between the top of the CV joint boot and the bottom of the strut to extend the strut bottom downwards. I haven't made the adapter yet, so it's only a concept at this stage but as you can see the jounce travel increases significantly to 110 mm. This idea came to me when 355Fiero (Don) thought at one point that I had installed the HT adapters upside down, which would have resulted in a similar looking adapter (though they wouldn't fit correctly that way). That's what's so great about this forum... so many different views coming together in one place.

This new adapter also has the benefit of offsetting the lower end of the strut further outboard, which moves the strut angle further away from vertical. That isn't always a good thing, but on the Fiero, it's a means to reduce the lateral movement of the roll center (that's one of the reasons the '88 has less distance between the strut tops than the earlier cars). Also remember from an earlier post that as the angle between the strut and the lateral links approach 90 degrees during jounce, the camber gain goes from negative to positive, which is a bad thing. Angling the strut by tipping the bottom outboard (or the top inboard) helps keep the relative angle between the strut and the lateral links under 90 degrees. In this case, the new adapter combined with the somewhat neutralizing effect of the angled lateral links results in a strut to lateral link angle of 71.9 degrees which is slightly better than the stock 73.5 degrees.

To accommodate this new strut angle, I've added a 5.9 degree wedge shaped spacer between the top of the strut and the underside of the strut tower. The upper bushing normally takes into account the angular change in the strut through it's bump travel (about 3.5 degrees total) but I consider 6+ degrees enough to warrant the spacer.

The overall 30mm chassis drop causes the axle and lateral links to angle upwards 3.6 and 4.3 degrees respectively, so they're redrawn in red.

I kept the angle of the trailing link constant by raising the forward trailing link mount on the cradle 30 mm's and so that's why the link isn't redrawn in red but the cradle is.

There are other things that happen as you shorten the springs: the half-track width narrows very slightly (1.1mm) and the CofG lowers as well.

Lastly, this drawing depicts a new profile for the rear fender to close the gap above the wheel. As mentioned before, at this stage it's worth actually having some tires and setting the body at the new ride height to see whether a 3" fender gap is way too much or borderline acceptable since the drawings can be misleading. I knew what tires I wanted, so I ordered them, and they're now in. I spent a couple hours playing with ride heights and the camera, so I've decided that while the 3" gap is still too large for my liking, I will analyze the performance data to see how much I lose by stepping up to stage 3B.

(edit: changed CofG height to account for combined effects of front and rear suspension drops)

[This message has been edited by Bloozberry (edited 08-18-2012).]

Blooz;

Great analysis on the rear suspension.

When looking at the fender height above the wheel, have a good look at the rear bumper and how the front edge of the rear bumper really raises up compared to the rear section. When lining the straight body line up front to rear as on oem, you will see that the front edge of the rear bumper will have to be lowered by about 1.5"-2" IIRC. Given you are at 3" with a 1" drop in the wheel well, you can probably get another 1/2" or more by leveling out the rear bumper to line up down the body.

You will find you need to adjust the rear bumper down, fender well down, body line in front of fender well and on rear clip down, door cut and just about 3/4" at the rear edge and about 1/2" at the front edge down and then rotate the front bumper rear edge down about 1/2" as well. This will line up the body line and lower your rear wheel well down to a better location to the rear wheel.

I will see if I can find my old pics of the body cut up and pasted back together before fiberglassing everything back together. And then try to figure out the pff upload tool again...

Keep up the posts as these are great to read.

Cheers
Don

Edit: Finish my sentences and spelling.... and I took your 3/4 side view and added lines to show how the body ends up being cut and pasted back together to make it acceptable. Red line is where the body line should be from end to end and the black lines are where I cut to reposition the panels to get the straight body line. Made a world of difference to the look of the car.

I put the photo on Photobucket as a start to see if it works. (works....)

[This message has been edited by 355Fiero (edited 07-04-2012).]

I snapped a few pictures the other day to give a better appreciation of approximately what stage 3A would look like. Remember, this isn't the look I want, it's just a better visual of what the drawings above are saying: basically a three inch fender gap is too much. First, here are the newly acquired rear meats... Goodyear Eagle F1 Assymetric2's:



And although this next picture doesn't actually have the fender reprofiling I've lowered the chassis on the wheel to show what 76 mm (3") looks like. From the side:



Edit to add:

And from the rear quarter view:

[This message has been edited by Bloozberry (edited 07-08-2012).]