The basic leaf-spring-style rear suspension used on early Mustangs is simple, yet it has provided good performance and reliability for many years. There are, however, a few subtle changes that can be implemented to make it even better. I do not get into the full-blown restomod or racing upgrades where the leaf springs are removed in favor of other designs using trailing links, watts links, coilover shocks, and the like. I simply provide a few recommendations on how to enhance the stock rear suspension for a weekend cruiser or even a daily driver. A show car being built with maximum originality will not utilize most of these improvements. Although, in most cases, the tips provided for installation still apply because the process is generally the same.
This Tech Tip is From the Full Book, HOW TO RESTORE YOUR MUSTANG 1964 1/2-1973. For a comprehensive guide on this entire subject you can visit this link:
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Budget-minded restorers can reuse the stock springs if they are in good shape and want no further improvement. They can either use directreplacement bushings and shackles or install upgraded items as budgets and personal priorities dictate.
The options we chose retain the basic factory design yet provide significant improvements in a relatively cost effective manner. They do lower the car a bit, but we like the way it looks. Unless somebody is going to get down on the ground and look under the car, this lowered stance and possibly the color of the Koni shock absorbers are about the only obvious clues that we’ve deviated somewhat from using direct-replacement parts to get better performance.
The Del-A-Lum bushings must be pressed into the spring eyes because they have a very slight interference fit to prevent them from rotating in the spring. The bolt that goes through the bushing, however is free to rotate as needed, and the side/thrust washers made of Delrin also have negligible friction with the shackles when they are properly adjusted. This allows them to also rotate freely within the shackle, thus improving the response of the spring while also reducing both overall ride harshness and initial impact harshness when compared to either rubber or polyurethane bushings. Perhaps, most importantly, the far greater stiffness of these bushings also helps minimize axle hop because these bushings can never get into a resonance with the spring. To the extent the spring may wrap up during a hard launch, either the tire slips or the spring unwinds, but it is almost impossible for the pattern to keep repeating itself with virtually solid bushings like these. Therefore, axle hop is highly unlikely to occur, especially on street tires and even with race tires. We won’t be getting anywhere near that type of test, so our main concern is the tradeoff between ride and handling which, as was stated, really isn’t a tradeoff at all.
A slight increase in noise or vibration over the rubber or polyurethane is about the only downside to using these bushings. Our experience with other vehicles running, these bushings have proven this to be negligible, at worst. After all, we are talking about a vehicle with sporting intent, not a luxury car.
Virtually no car from this era could truly be said to have had very refined ride and handling by today’s standards, and any concerns of a bit more noise and vibration quickly fade in comparison to the greatly improved handling, braking and durability, etc.
Written by Frank Bohanan and Republished with Permission of CarTech Inc