What I Learned From a Chassis Bracing System

Categories: Collector Cars.


Rebuilding My Totally-Not-Collectible Mustang, Part VIII

The Stephen Cox Blog is Presented by National Parts Depot 

Guess what I just learned after 40 years of driving Mustangs? The stock suspension on an early Fox body Mustang actually isn’t that bad. It’s certainly not great, but I was shocked to learn that it’s actually somewhat serviceable as far as 1980’s technology goes. 

Known as Blue Thunder, my 1980 Mustang has never had anything other than factory-recommended springs and struts. I’ve found them perpetually unsatisfactory with too much body roll, poor turn-in on corner entry and insufficient insulation from the bumps and potholes that sadly characterize what remains of American roads. 

But all that changed when National Parts Depot recommended Stiffler Chassis & Suspension’s FIT System. The in-house designed chassis bracing system is next-generation technology compared to traditional subframe connectors. A steel girder system welds to strategic stress points of the unit body to create a racecar-like feel with the added benefit of being able to use the entire frame length under the rocker panels to jack the car without fear of punching through the floorboard. 

The real treat, however, is the first drive. We began with 55 miles of street testing at average road speeds and my Mustang instantly felt like a different automobile. Not just a newer automobile – but a different car entirely. And a better one. 

Turn in was crisp. The ride was smoother. It didn’t take long to realize that this tired old warhorse (with nearly 250,000 miles on the clock) had so much chassis flex that the suspension hadn’t been working for years. It didn’t need to. The slop in the unit body was absorbing all of the turns, twists and bumps. The stock suspension simply wasn’t working. The springs weren’t compressing and the struts weren’t rebounding. The unit body was flexing to absorb all of the work that the suspension should have been doing. 

WIth the FIT System in place, the unit body was nearly as rigid as most of the race cars I’ve driven. The suspension was working again. Okay, let’s be realistic… no one wants to take a stock Fox suspension to race at LeMans. It’s not great. But surprisingly, it’s not that bad either. 

With our preliminary street work done, we then took Blue Thunder to a designated course for testing at higher speeds where the car’s McGunegill 347 cubic inch Ford V8 easily soared into triple digits. I had the car up to 116 miles per hour – still pulling like a freight train in 4th gear – and was able to maintain speed for nearly half a mile before running out of straightaway. The car was so stable and predictable that I was literally able to rest my left arm on the window sill for a few seconds between corners.  

Before installing the FIT System, the car didn’t really like these speeds. It felt nervous and darty on the straightaways. Steering response was slower. The car tended to wander. But all of that disappeared with the installation of the FIT System. If a longer straightaway can be found, I wouldn’t be afraid to test the limits of the engine and see if we could break 150 mph. The car felt solid enough to give it a try. 

And there’s more. We hope to augment the FIT System with a new cross member, tubular K arms and drive shaft loop in the near future. So stay tuned for the next chapter in this story. It’s gonna get even better.

Stephen Cox 

Driver, FIA EGT Championship, World Racing League, CRS Truck Series 

Co-host, Mecum Auctions on Motor Trend TV 

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