128 Suspension Modifications
Ok, after scanning through the Tech Questions/Answers and X1/9 Racers Forums, I've compiled the 128 Suspension Modifications FAQ:
Q: How do I lower the FRONT of my 128?
A: There are two practical methods of lowering the front of a 128. The first, and better, method is to install a pair of '74-78 X1/9 rear struts and springs. You will use the top mount of your 128 on these struts as the X1/9 mount is different. This method will lower the front dramatically without stiffening it up too much (like when you cut springs) and maintains the right amount of travel so it won't bottom out the strut (another drawback of cutting springs). Some negative camber will also be introduced, which will improve handling.
The second method is to cut your stock 128 springs. Removing 2-3 coils will lower it significantly. However, a result of cutting the springs is that they will stiffen up, giving a harsher ride. Also, if too many coils are removed, the strut has the chance of bottoming out. I cut 2-1/2 coils off the springs in my 128 sedan and never had any problems however.
If you lower the front of a coupe too much you need to shorten the tie-rods to retain proper toe setting. Watch out for this! One other note is that the coupes have shorter springs than the sedans anyway, so using the X1/9 struts may not have as dramatic an effect on the coupes as the sedans.
Q: How do I cut the springs on my 128?
A: To cut the springs, you need an electric or compressed-air tool with a disc for cutting metal - it will take several years with a hacksaw! Decide how many coils you want to remove (2-1/2 recommended) and cut away. It is best to use a torch to bend the end of the cut spring level enough to sit even in the seat. However, I didn't do that when I cut my springs, and as long as you reassemble them carefully, you shouldn't have any problems with them falling off the perch.
Q: How do I lower the REAR of my 128?
A: Space the spring perch away from the A-arm. You can either make threaded spacer blocks to screw onto the existing studs, which the perch mount on, and then bolt the perch to the bottom, or knock out the studs in the A-arm and put longer bolts through (putting something around the threads as a spacer). The ride-height may be adjusted by using different sized spacers. Here's a photo of the setup:
Make sure you move the brake compensator connection (form "A" to "B" on the photo) so the compensator still functions properly.
It is also possible to lower the rear by removing a leaf from the leaf spring assembly. I do not recommend this as it would make the rear suspension rather soft, making it easier to bottom out, and induce body-roll.
One note of caution: if you lower your 128 and are running wide tires it may be necessary to roll/hammer the wheel arch lip to prevent rubbing
Q: Can I stiffen the rear of my 128?
A: Yes. This can be done by adding a leaf to the leaf spring assembly. The ideal situation would be to find a 128 wagon to donate its rear spring. This has a third, short spring which adds stiffness. Wagon springs are tough to find but a leaf could probably be added from another 128 spring assembly. The clips that hold them together may need modification, but it shouldn't be too difficult an operation.
Q: How can I make my 128 handle better? Would swaybars help?
A: To make your 128 handle better it is best to lower it. If you don't want to change the ride height, then adding/changing a swaybar is your next best option. In stock form the sedans have a small front swaybar, the wagons have a large front swaybar, and the coupes do not have a front swaybar. None of them have a rear swaybar. Adding larger front swaybar, while it will reduce body-roll, will only increase understeer. The better option would be to add a rear swaybar. This will give the car more neutral handling, and decrease body-roll. For racing purposes it may be desirable to add a larger front swaybar in conjunction with a rear swaybar. The larger wagon swaybar will fit on the front of a sedan. Addco Industries (http://www.addcoindustries.com) produces larger diameter front, and rear swaybars for 128s.
Q: What options do I have for performance shocks/struts on my 128?
A: Sadly, the options are rather limited. It seems KYB has stopped producing struts for the X1/9s so they cannot be purchased for the front-end lowering of a 128. If you manage to find someone who has some, snatch them up! Sears sells Gabriel strut cartridge inserts for the '74-78 X1/9s. Those X1/9 struts can be disassembled and the inserts installed. You can rebuild the standard struts by pulling them apart, cleaning them well and putting a multigrade oil like GTX2 in them.
Q: What wheels will fit on my 128? What size tires?
A: Most any Fiat wheel with the 4x98 bolt pattern will fit on a 128. The offset, however, might not be correct for the application, and may create wheel-rub. Lancia Beta wheels work nicely since they are 14x5.5 alloy wheels with a front-wheel-drive offset. They look great on a 128 too!
The largest practical tire size that will fit a 128 is a 185 series. These will require some rolling of the rear wheel well lips if your car is lowered. Anything larger would probably require fender flares or other serious modifications.
The answers in this FAQ were gleaned and butchered from the Forum posts of the following Fiat nuts: Marc Frost, Paul Sutherland, Dwight Varnes, and Courtney Waters.