When I bought the partially completed car, the previous owner had permanently bonded the rear fibreglass quarters and roof to the chassis. When I decided to remove these panels for greater access to the underlying frame, one of the surprises that struck me was that he had made no provisions for a rear bumper bar. The rear frame horns weren't connected in any way, and the stock bumper bar had obviously been thrown away. This certainly wouldn't have passed inspection in my province, nor would I have accepted such a modification knowing first-hand what it feels like to be in a rear-end collision in an unmodified Fiero. So the next step was clear: make a new structural bumper bar.
Luckily I had an '85 parts car that I could take some measurements of the stock bumper bar from, to get some idea where to start. Though it was hopelessly rusted, it still offered up the basic dimensions:
I drew it out and added it to my frame drawings for reference. Next up was to get an accurate profile of the rear fascia to know how much room existed between it and the hidden chassis behind it. I mocked up the rear fibreglass quarters to measure where the bumper fascia sat in relation to the frame:
Then I used a small profile gauge and a level to trace the approximate shape of the rear fascia. It wasn't large enough to do it all in one shot but by being careful to hold the gauge perfectly vertical, and by making a bunch of overlapping reference marks, I managed.
After each impression, I traced the profile section onto a large piece of cardboard, then cut out the template and test fitted it to the actual car to make the final adjustments:
Once the shape was about as good as I could get it using this method, I used the data points to draw and locate the fascia's profile electronically on my chassis drawings. With all the pieces of the puzzle laid out it became obvious why the previous owner had removed the bumper bar altogether. Here's how much interference there would be without modifications: the blue shaded pieces represent the plastic honeycomb structure:
Even without the honeycomb material it was clear that the rear fascia and the bumper bar tried to occupy the same space. I considered a few options and decided to keep the stock style bumper bar and recess it only to the extent necessary (50mm) to get the metal bar to clear the fibreglass fascia like this:
With that decision made, I removed the rear quarter panel once again and got cracking on the underlying metal modifications. The rail halves that I got from my friend Graham were already shortened but I still needed to lop off 2" from the original portion of the rails. The left-most black line shows where it needed to be cut back:
It was quick work with the cut-off wheel in the angle grinder:
After some careful cross-checking, I relocated and pinned the bumper bar mounting flanges into their new positions:
Then I fired up the small MIG welder and joined the flanges to the shortened frame horns:
Next up: fabricating a new bumper bar.