The Working Principle of Independent Front Suspension (4)

Overall, with the vast plethora of Mustang II-style IFS kits ranging from basic budget setups to fully polished showpieces on the market today, there is very little reason to go with a used Camaro front clip.

PROPER SETUP AND COMMON PROBLEMS

As you set up your new IFS system, the ride height and stance should be roughed out before you install any of the suspension parts. Put the frame on jackstands and position it at the angle and rake you want, then start mocking up parts. Most manufacturers sell pre-cut crossmembers that have a small amount of rake built in, so the member itself sits flat on the frame. Once the crossmember has been bolted or welded in and the suspension pieces are installed, ride height can be estimated by installing the springs and shocks. It is vital to remember at this point that the true ride height of the car cannot be determined until the engine, transmission, and all necessary fluids have been added to the car. Once the full weight of the car is resting on the springs, they will settle over a period of days or weeks. All too often, first-time builders get frustrated when their new IFS system looks like something that belongs on a 4x4 and begin hacking or heating coils, only to find out later that their car now rides like Fred Flinstone's roadster because the suspension has bottomed out.

When choosing and installing IFS, a vital and often overlooked consideration is the location of the rack-and-pinion, which can affect toe change as the suspension moves throughout its range of travel. The lower control arm and the tie rod that connects the rack to the spindle need to work like a parallelogram. If the tie rod is at a different angle because the rack is mounted too high or too low, trouble will follow.

"What happens most often is that a guy will install a rack in the wrong location because it will only fit a certain way, and all of a sudden the car will have terrible bumpsteer," says famed chassis designer Art Morrison, proprietor of Art Morrison Enterprises. "When the suspension is not parallel, every time the tire hits a bump and the spindle goes up or down, the wheel will actually turn." For an in-depth explanation as to why bumpsteer occurs, see illustration number three.

Finally, the experts all warn about the use of power steering on pre-WWII hot rods. While fat fender cars and later-model customs have plenty of mass to move around, early Fords are very light up front and are not heavy enough to put the necessary load on a standard power rack-and-pinion system. As a result, over-correction becomes a problem, and the car will dart around with little or no road feel. Most people do not realize that rack-and-pinion steering requires far less effort to turn than a standard steering box, so power usually isn't necessary anyway. If you absolutely must have assist, there are a few safe options available, including retrofitting a late-model Fox-platform Mustang ('79-93) power rack-and-pinion setup or finding a shop that can reduce the line pressure.

ALIGNMENT

Proper alignment is always vital on any car, but things can get tricky if you aren't prepared when you walk into the alignment shop, especially with an IFS under the fenders. "When swapping suspensions, the heart of the idea is to make the spindle think it's in its original home," VanDervort says. "Believe it or not, I've heard of shops trying to use '40 Ford axle alignment specs on a Mustang II front suspension just because it's in a '40 Ford!"

By using the manufacturer-supplied alignment specs for the spindle, your new IFS should work as well as it does in a brand-new car, if not better. The kit manufacturer should supply all alignment details, and the following information should be used as a loose guideline only. Camber on an IFS-equipped car with radial tires is generally set around 0 to 1 degree positive, which puts the top of the tire slightly outboard of the bottom. This creates a tendency for the tires to turn toward the vehicle centerline, providing straight-line stability.

Toe-in keeps the car tracking straight as it moves down the road, and with radial tires somewhere between 1/16- to 1/8-inch toe-in works pretty well according to VanDervort. While the car is underway, this is usually reduced to 0-inch as any slack in the steering system comes under the pressure of driving.

"Caster is where things get interesting," VanDervort says. "By leaning the kingpin angle back somewhat, an effect is created where turning the wheels raises the car. Therefore, the car's own weight attempts to push the wheels straight again. As you can imagine, more caster provides increased straight-line stability at the expense of harder steering. Bonneville cars often run up to 15 degrees positive caster to gain the stability they need at ultra-high speeds." For a more in-depth look at caster, see illustration number seven.

CONCLUSION

As you can see, there are quite a few different ways to choose and dial in an IFS system, but with the proper research and a little time planning, just about any rod or custom can benefit from modern engineering with better handling, a nicer ride, and an improved driving experience.

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