The use of an adjustable coil-over type strut is desirable because it allows for easy adjustment of ride height and spring rate. I don't know of any aftermarket vendors who supply coil-over struts for the 128 (not in the US anyway) so I set out to make my own. I acquired a set of Ground Control threaded aluminum perches and Eibach springs (from a junkyard Honda) which I used for this conversion. The springs have a 2.5" ID. The price was right - I paid less than $20 for the perches and springs! The springs were too stiff for my use (300lb/in) but my friend had a pair of 200lb/in which I was able to use. The struts are rear '74-78 X1/9. They can be disassembled so various cartridge inserts can be used in them. These were also junkyard units, which to my surprise came with a set of decent KYB gas inserts. The X1/9 strut has a shorter piston than the 128, so a 128 can be lowered significantly without risk of bottoming the strut.
I have written the following instructions for building your own coil-over struts:
| 1. Disassemble the strut. Drain all fluid and remove all internal parts. Disassembling the strut allows you to grind and weld on the strut tube without damaging the internal parts or risking the possibility of the strut exploding from the heat generated by those processes. | |
| 2. Remove stock spring perch. I cut the perch from the outer edge to the strut tube in two places. Then I carefully ground off the weld bead that holds the perch to the strut tube. Once the bead had been ground down, the two perch halves came off easily. |  |
| 3. Machine spacers for threaded aluminum tube. In order to fit the threaded aluminum tube to the strut, spacers had to be fabricated. I machined these on a lathe. Material was simply mild steel tube. The top spacer serves only to locate the aluminum tube with respect to the strut tube. The bottom spacer locates the aluminum tube and positions it vertically on the strut tube. |  |
| 4. Weld spacers on to strut tube. I cut the spacers in half and welded them to the strut tube. I positioned the spacers so the top of the aluminum tube would be flush with the top of the strut tube. I was particularly careful about making sure the weld on the bottom spacer had good penetration and went all the way around the spacer since it would be taking transferring all of the load from the aluminum perch & tube to the strut tube. The top spacer wasn't as important as it would only be taking loads normal (perpendicular) to it, effectively pressing it against the strut tube. |  |
| 5. Install threaded aluminum tube and perch. Before I could install the aluminum tube, I had to do some finish grinding on the spacers to make the aluminum tube fit properly. I made sure it was a snug fit so it wouldn't rattle while driving down the road. |  |
| Another view of the strut with aluminum tube and perch installed. |  |
| 6. Machine upper spring perch. The Honda I pulled the coil-overs off of had an "interesting" setup where the upper end of the spring actually perched on the body, with a rubber pad to keep it from rattling around. My suspension is quite a bit different, so I had to machine some upper spring perches. I designed it to use the stock Fiat upper mounting hardware. Material is 6061-T6 aluminum. |  |
| 7. Install spring, upper perch, and mounting hardware. The fiber washers that the whole top mount assembleis pivot on were cracked as usual. I replaced them with a custom unit designed by Mark Plaia, which uses a roller bearing. The unit would fit a stock strut assembly as well and it really makes the steering smooth and responsive! |  |
| Another shot of the final assembly. |  |
| Here is the assembly installed in my Rally! |  |