Ford Mustang Suspension System Technology
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.
If complete adjustability...
If complete adjustability from the cockpit is your desire, then an air suspension from Air Ride Technologies would definitely fill the bill. This compact control panel in the car gives you complete control over ride height and rake at the touch of a button. It's also a great way to go if you have a widely varying load range when using your vehicle. If you've got 100 pounds of luggage in the trunk and three passengers on your way to that long distance car show, adjusting the ride height to compensate is a cinch.
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.
The AirRide system fits in...
The AirRide system fits in this spot in our story because, although it's a radical upgrade, it still uses the stock mounting configuration in the front suspension. This shot shows how the AirRide front unit goes into position in place of the standard shock absorber, between the upper control arm and upper shock tower.
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|
The rear suspension available...
The rear suspension available from AirRide is somewhat more involved. The rear axle is located by upper and lower trailing arms, converting a classic Mustang to a rear four-link system. The system features advanced suspension geometry and the fact that air doesn't transit between shocks means that they have an antiroll function similar to a rear antisway bar.
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.
The next type of suspension...
The next type of suspension we'd like to consider is one where the upper control arm is completely eliminated. This McPherson strut arrangement is very similar to that found on newer Mustangs, and simplicity and fewer moving/wearing parts is a main advantage. Kits are offered from several sources including Fatman Fabrications, Gateway Classic Mustangs, and Anthony Jones Engineering (AJE), which is shown here. The strut system is a bolt-in that requires a solid shock tower, but if you decide to trim the shock towers back for more room, then welding is involved. Rack-and-pinion steering is mandated with this late-model-style front suspension setup as well.
Another strut system that...
Another strut system that tackles a whole bunch of issues with the classic Mustang front suspension is the Performance Suspension Module (PSM) from Fatman Fabrications. The PSM is a complete tubular front suspension assembly that incorporates a new engine compartment "cage," inner fender panels, late-model Mustang struts, brakes, and more. Shipped as a bolt-on component, you have to have the assembly finish-welded after you've bolted it together yourself. The PSM gives you modern steering, suspension, and braking, while offering tons of room for engine swaps, and for those with high horsepower builds it properly channels the power through the firewall and rockers, something the typical Mustang II does not, without additional bracing. All stock sheetmetal bolts directly to the PSM as well.
For those of you who want...
For those of you who want to upgrade your car to front disc brakes, rack-and-pinion steering, and coilover suspension can kill all three birds with one stone using the Mustang II frontend conversion kit from Rod & Custom Motorsports. The fourth big incentive to going this route is the complete elimination of the vehicle's shock towers. For those of you thinking of a way to put a 460 into a Falcon or a 5.4L GT500 engine into a Mustang, this is the way to go. Welding and careful measuring is involved in this installation.
A similar kit from Heidts,...
A similar kit from Heidts, called the Superide II, features a weld-in crossmember, rack-and-pinion steering, coilover shocks for full ride height adjustment, and tubular control arms top and bottom. This photo is from our in-house '68 Mustang project. The substantial under-the-engine crossmember takes the vehicle weight instead of the shock towers, leaving plenty of room for an engine swap/conversion of your choice. Many manufacturers offer a similar system with numerous options like coilovers and power rack-and-pinion steering. Think of Heidts, Rod & Custom Motorsports, and Total Cost Involved (TCI Engineering) when considering an upgrade of this type.
Just about every one of the...
Just about every one of the Mustang II-based front suspension companies offer a bolt-in multi-link rear suspension system, and that includes TCI, Fatman Fabrication, Rod & Custom Motorsports, and Heidts (shown here, again on our project fastback). Utilizing stock mounting points on the classic Mustang's chassis, the axle housing is positioned in the wheel opening and then controlled laterally by either a Panhard bar or other linkage. The Heidts system is a four-link arrangement that uses bolt-in pickup points and a Panhard bar. Some welding is required for the axle housing brackets.
If eliminating the shock towers...
If eliminating the shock towers is on your agenda but you don't care for the Mustang II configuration, then this GR-350 front suspension setup from Griggs Racing may be a good way to go. It's a very sophisticated arrangement designed for road racing and great street performance that also eliminates the towers from underneath the hood. Because it's fully tunable, adjustments can be made for any type of track condition.
The installation is involved...
The installation is involved with the Griggs kit but the results are well worth the effort. The system offers great adjustability, and as you can see it leaves the engine bay unencumbered by shock or spring towers.
This is the Griggs GR-350...
This is the Griggs GR-350 kit for the rear of your classic Mustang. The coilover and trailing arm arrangement also eliminate the leaf springs. Even without the surrounding cage, like some rear suspensions, the GR-350 rear system still manages to incorporate a true Watt's linkage and torque arm for the ultimate in rear axle control.
This photo of the upper control...
This photo of the upper control arms we used shows how they are reinforced with additional plating to increase strength and have the shaft ends welded to prevent loosening or walking off the pivot shafts. They were installed onto the car using the 1-inch drop position, ala the '65 Shelby GT350. Our setup had a revised ball joint location that repositions the upper ball joint to restore complete control arm travel without binding.
Compare the reinforced lower...
Compare the reinforced lower control arm at the top to the stock arm we removed. Together with the improved bushing material the bolstered arm will offer much better control over the position of the wheel.
This photo shows the "racing...
This photo shows the "racing style" rear leaf springs, which are configured as a five-leaf from the front mount to the axle and then three-leaf from the axle rearward. The heavier spring structure in front helps prevent axle windup, like a traction bar, while the lighter weight at the rear of the spring helps ride quality and suspension compliance.
This photo shows the Panhard...
This photo shows the Panhard assembly in place on the car. We felt that the Panhard rod was a big part of the success realized with our suspension upgrade, and the problem of the tire sidewalls contacting the wheelhouses disappeared and the back end of the car became much more controllable.
The rear suspension upgrade...
The rear suspension upgrade also included replacement poly bushings for front eyes as can be seen in this stock versus modified photo. Also included in the upgrade for the rear were poly spring shackles and Bilstein shocks.