Wayne Cook
June 25, 2010

Tech | Suspension Upgrade
As we go through our classic Ford cars, making them better, one of the departments many of us are concerned with is suspension. While the stock underpinnings are adequate for most things when in good repair, there is definitely a lot of room for improvement. A modern wheel and tire selection can make a huge difference in how your vehicle rides and handles, but for further improvement we often delve into suspension modifications. Even if left in a completely stock configuration, there is a lot that can be done to enhance the handling prowess of your classic Mustang or other special interest Ford. Many suspension companies now offer improved stock components that have additions like boxed control arms for increased rigidity or easily replaceable ball joints. Other stock component improvements include the replacement of rubber bushings with urethane units, while others might include heavy-duty versions of a stock part, such as antisway bars. Certainly the replacement of OE shock absorbers with more modern units such as those made by KYB, QA1, Koni, or others will offer improved suspension control.

When we decide to go beyond the parameters of the stock configuration, there are now so many choices that it can be bewildering which direction to choose. Much of your choice should be dictated by what you like to do with your car. Certainly a drag racing fan will have different requirements than someone who is interested in road racing. For example, while many drag racing fans will install 90/10 shocks and remove the front antisway bar to improve weight transfer, these modifications would be the last thing a road racer would want to do (and can be fairly dangerous to drive on the street).

For flat cornering, a larger-than-stock front antisway bar and shocks that control the wheel in both directions (both jounce and rebound) would be much more useful. Still others who are interested in more power in the form of a different engine would go yet another route, allowing the fit of said engine.

Many kits are now available to allow the removal of the original shock towers, thus enabling the installation of a larger-than-stock engine. In the creation of this article we talked to many different suspension manufacturers to get their takes on why these different selections work the way they do and the different advantages they offer. Let's take a look at some of the different suspension options out there and how they offer different advantages over other types of suspension, including the stock setup.

Align It In Time Many of us will choose to do our suspension upgrade project in the home garage with a floor jack and a set of jackstands. Keep in mind that once a front suspension swap is completed, you're going to need an alignment, no matter how careful you've been to retain the old settings. Matter of fact, most aftermarket suspensions come with suggested alignment specs to make use of the better handling inherent in the new suspension's design. In addition, remember that the drive to the alignment shop should be a short one and be done right away. If that's not possible then make arrangements to trailer the car to an alignment shop. Even 25 miles on a set of tires with the front end out of whack can be enough to badly damage a set of new tires; not to mention it's unsafe to drive with such poor alignment settings.

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Track Day Testing
The object of any suspension upgrade is to improve handling performance. For this review we wanted to see exactly what gains could be realized on the ground after a substantial suspension upgrade. It's one thing to say that the car feels better in turns and has less body roll but we wanted to be able to quantify improved suspension performance in a measureable way, so this comparison was envisioned. We put our subject vehicle, a '68 Mustang coupe, through its paces at Mid-America Motorplex in Pacific Junction, Iowa. Before we installed the new suspension components, which included both front and rear direct-fit bolt-on upgrades, we tested our car out on the 2.23-mile road course. While the car handled OK on the stock replacement suspension, we still had our hands full trying to keep up with traffic on the course, such as the late-model Corvette seen here. On our best run we were able to complete one lap of the road course in exactly 1.55.00 minutes.

It should also be noted that at the time of the rebuild the worn stock front springs were replaced with shorter 620-lb/in springs and the front antisway bar was also upgraded to a 11/8-inch. The only other suspension modification was the addition of a rear antisway bar. The old suspension had less than 1,000 miles on it, so our test car wasn't a basket case. Even with the newer control arms and larger-than-stock sway bars, out on the track there was a lot of room for improvement. The front of the car pushed on nearly every corner (understeer) while the rear was somewhat unpredictable. Any bump or extra throttle would cause the rearend to lose traction and begin to oversteer and it would have been easy to spin the car. A big issue with the rear suspension was the amount of lateral movement and the 285mm section width tires rubbed on nearly every corner.

Other than driver impressions, track times and tire temperatures were also recorded. Track times are a simple way to keep tabs on how fast and consistent the car handles going around the course and tire temperatures give us a good idea of how effective the suspension is in keeping the tire's contact patch on the road. In the initial test, the track times were consistently in the 1:55.5 ranges with a best time of 1:55.00. Front tire temperatures were consistent throughout the day. We measured the tire in three sections including inner, middle, and outer. The results indicated that the suspension was not allowing the entire width of the tire to work. The outer tire temperatures throughout the day were nearly 20 degrees warmer than the inside of the tire.

For our track testing we installed new reinforced/boxed upper and lower control arms, new spring perches, and new urethane bushings up front; and new leaf springs and a Panhard bar in the rear. The new suspension components used are based on the stock configuration but were designed to improve both suspension geometry as well as component strength. All of the new equipment included more rigid bushings with most of the parts being direct bolt in.

Once the install was complete, the car went out to Mid-America Motorplex once again and the results were impressive. In our "before" test, the car felt like it was at the edge of its performance envelope at many points on the track. However, after the rather simple bolt-on suspension upgrade, the car felt more solid and confident in every aspect. It was more predictable on turn-in, the car understeered less through each corner, and the rear end remained planted regardless of what was done with the throttle. In the initial test, there was no need for more power. The suspension was clearly the weak link. But, with the new equipment more power could have been utilized. From a numbers point of view, the results were impressive. Average lap time with the new suspension was in the mid 1:52s with a best lap time of 1:51.00. This is a significant gain of more than 4 seconds as a result of changing the suspension. These gains were seen without the use of a rear sway bar, and with the same alignment specs from the initial test.

Average Tire Temperatures Recorded
BeforeInsideMiddleOutside
Left Front160188190
Right Front162186188
After
Left Front164174175
Right Front162170172

Because we were using the same alignment specifications, the temperature scales indicate that we were better able to use the whole tire contact patch with the new suspension. While there is still some room for improvement, it was significantly better than the initial setup. We'd like to offer our thanks to the guys at KR Performance & Restorations [www.krpandr.com; (402) 799-2056] for installation, track testing, and keeping great notes of the day's results.

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