Tom Wilson
April 1, 2007

Horse Sense: When we arrived at GTR's shop, it didn't take long to recognize the neighborhood. The new place is literally a stone's throw-just over the back wall and across the street-from Kenne Bell's speed emporium.

These days, it just won't do to run around at stock ride height. Credit the lowriders and race-car folks for setting the trend, but today's 'Stangers feel the need for weeds-up around their fender tops, that is.

While there are several ways of getting a Mustang down to the ground, the most effective and adjustable solution is via a coilover spring/shock system. Coilovers are nifty because they were developed by racers to adjust the ride height of race cars. Thus, they are built with a set of threads around the outside of the shock onto which a threaded collar is installed. The coil spring is then lowered over the top of the shock and onto the collar, while the top of the spring is retained by a plate or collar attached to the chassis. So, screw the collar at the bottom of the spring up or down to raise or lower the car body.

For the street Mustanger, this means coilovers are perfect for setting ride height for any need. Will you be jetting around town, running errands, commuting, avoiding that nasty railroad-track crossing, or touring? Then run the ride height up an inch for ground clearance. Doing the lawn-chair laze at a car show? Thread your 'Stang into the grass when you get there. Gonna take the plunge and run an open track or scare cones at a slalom? Set the ride height to where the car needs to be.

We don't mean to say running the ride height up and down is so easy you'll do it on a daily basis. In the real world, setting ride height is something for track days, special car shows, or even just once to get that street look right. And that's OK. Modifying your car means getting it just the way you want it.

For the newest S197 Mustangs, we have the Competition Series coilover system kit from chassis specialist Progress Group. It was shown to us by the always-busy crew at GTR High Performance, and it was installed on a customer's Stage I Roush Mustang.

Despite its name, the Progress Group kit is aimed to at least accommodate the street crowd, as opposed to strictly pandering to racers. It's simpler and less expensive than many coilover kits, yet it provides the adjustable-ride-height people want. But it also features sophisticated damping and is definitely track-worthy, "especially when matched up with our Progress replacement Panhard bar, and front and rear antiroll bars," Jeff Cheechov says, the mainspring at Progress Group. "This system will work well on track days, and be an acceptable daily driver."

In front, the Progress Group kit uses conventional coilovers-there is a strut that's threaded on the outside, an adjusting collar, and a typical 211/42-inch coilover spring that comes in a wonderful variety of spring rates from many sources and is surprisingly inexpensive. For the rear axle, however, Progress Group has gone to a more expedient route. The company retains the stock-style shock and separate coil spring, but by substituting a shorter, smaller-diameter coilover-type spring sitting on a threaded, adjustable perch, the ride height is adjusted the same way as a traditional coilover, making it fully adjustable at all four corners over a 3-inch range. Throwing scrapes sort of lowering is available, if that's your thing, or high-water pants if you insist. Spring rates are 350 pounds front and 250 pounds rear. That's stiffer than stock, but hardly unstreetable.

Because the rear arrangement uses a commonly available, stock-type shock and not an exterior-threaded racing-type shock, costs are contained.

For our article, Progress Group packaged its coilover kit-springs, shocks, front sway-bar links, adapters, and hardware-with its adjustable 35mm tubular front and 24mm solid rear sway bars and adjustable Panhard bar. As it turned out, the subject car provided by GTR High Performance already had Progress Group sway bars installed, so there was no need to change them.

To sum up the parts involved, Progress Group supplied us with the following facts:

Description Part Number MSRP Street Price
Coilovers 75.0807 $1,599 $1,279
Panhard kit 14.0807 249 199
Front adj. sway bar 61.0807 249 199
Rear sway bar 62.0807 229 183

Installing the Progress coilovers is not particularly difficult, but it still takes a pro installation because of the tools involved. The rear springs and shocks are easy to change, and if you have the inclination, you might want to swap those yourself. Up front, the trick is dealing with the stock springs, which are contained under compression by the strut and upper strut bearing/retainer. This combination must be disassembled, and it requires specialized spring compressors. All tire/ alignment/chassis shops have the required tools, and for maximum economy you could remove the stock strut/spring assemblies, bring them to the local tire shop, and professionaly have the springs taken out.

Under no circumstances should you attempt self-directed on-the-job training in spring removal using baling wire and zip ties. Automotive springs contain tremendous energy and are serious business when compressed. Take them to a pro to avoid injury or worse.

As we went to press, Jeff Cheechov advised us that he has moved to his own private-label units. The move was primarily driven by a desire to achieve custom shock rates, he says, yet the ride remains good due to approximately the same high-speed valving. Speaking of ride, we gave the final installation the once-around-the-block trial, and while it's impossible to give a detailed ride and handling report from only that, suffice it to say the coilover kit has an acceptable, daily-driver ride quality, and looks good doing it.

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