For any serious Pro Touring build, one of the first questions any owner should ask themselves is whether or not to utilize an aftermarket chassis. Even factory unibody cars like the first-gen Camaro and Firebird have the option – and for good reason! One of the primary goals of any Pro Touring build is to equal or surpass the handling of a modern sports car. It is hard to do that if the foundation of the build is over fifty or sixty years old.
Sure, there are ways to strengthen the stock frame, but many enthusiasts also need to notch the frame for rear tire clearance. This can also weaken it. Not to mention, it is quite a bit of labor, and if you aren’t doing it yourself – this is not a cheap affair. At the end of the day, it will still be hard to compare to the advantages you get from going to an aftermarket chassis, which is designed from a clean sheet of paper. We spoke to Dale Schwartz of Schwartz Performance to get a full understanding of why some of the fastest cars (and trucks) in the Pro Touring scene are using their chassis – including our upcoming GM A-body project, aka Project Payback.
There isn’t one aspect that we feel the stock design has going for it, over our chassis. The only things we used off the stock chassis are the body- and bumper-mount locations. Everything else is completely different. – Dale Schwartz, Schwartz Performance
Let’s Talk Torsional Stiffness
The Schwartz Performance A-body chassis boasts a 200% increase in torsional stiffness over a factory frame. Forgetting for a second that your car or truck is trying to laterally accelerate, remember: the engine and drivetrain are rotating. As the crankshaft is spinning, so is the driveshaft and, in turn, the ring-and-pinion–therefore the posi and axles. This creates a twisting force that causes torsional flex or deflection. A 640hp LT4 crate engine, for example, has gobs of chassis-twisting torque nearly off idle, as does your average big-block.
“Flex means there is something being lost. It is not direct,” Schwartz weighed in. “Chassis flex can result in the suspension being unpredictable. Say you hit a bump on one side of the car. The sudden shock may flex the chassis slightly instead of the SHOCK ABSORBER doing its job. In street driving, this may not be very noticeable, but it is in racing. On stock suspensions with rubber bushings, flex is more apparent because it’s bound up by rubber. That’s why you get a performance gain by installing different style bushings, or bearings in the suspension.”
While the stock frames are C-channel, meaning not fully boxed (except convertibles and the longer wheelbase El Caminos and wagons), Schwartz utilizes ⅛- and 3/16-inch structural steel that is mandrel-bent to shape. A series of cross-braces goes beyond the factory design to provide added rigidity. “We gain the most strength through the mid-section and around the rear axle,” Schwartz stated. Typically this is an area that is difficult to re-strengthen when you are talking about clearance for a 12.5-inch wide wheel like the Schwartz GM A-body chassis can fit.
Overall, Schwartz feels this is just a better way to go. “A stock frame with big horsepower and [ample] traction will flex the chassis very easily. Rollcages can be added, which help, along with boxing plates and such. But that is added weight. Ours is stronger but lighter; that’s the key point.”
Too Much Horsepower, Not Enough Traction
There are quite a few suspension systems on the market to upgrade a car or truck with a leaf spring rear suspension to a four-link, three-link, or even an independent rear suspension. By going with an aftermarket chassis, all of the hard work is done for you. Thankfully, GM A-bodies have a simple but incredibly effective triangulated four-link from the factory. Schwartz maintains this design for a very good reason.
“A triangulated four-link is a very simple and all-around suspension style. The main disadvantage of a triangulated four-link is they can bind when one wheel hits a bump when going around a sharp corner where one wheel is moving differently than the other. However, on our four-link, we use Teflon-lined spherical rod ends (aka Heim joints) which eliminate this issue. In turn, it rides closer to how an IRS would feel. Additionally, pinion angle and instant center are easily adjusted (we have adjustable lower link heights on our frame for the latter). You can also easily center the wheel in the quarter-panel opening. We feel by having all of this adjustability, it’s a very universal setup for different types of driving.”
While some think that rod ends should not be used on the street, Schwartz has a very succinct rebuttal. “Spherical rod ends often get a bad reputation, but the only reason is whoever said that, was using cheap rod ends. We’ve experimented with dozens of manufacturers, and have been happy with just a few. The supplier for ours is FK Bearings. They utilize a heavy-duty Teflon liner between the ball and housing. This keeps them quiet for a long time. If one of them eventually goes bad, they’re extremely easy to replace, without use of a press. FK Bearings supplies bearings for the most hardcore racing series: Baja and others. Those racers are extremely tough on their equipment, in the worst of conditions.”
Bringing Race Car Tech to the Street & Autocross
Going beyond just the stiffer and lighter chassis, the discussion of rod ends leads us to an overarching concept with the Schwartz Performance chassis. A clean-sheet design allows you to seamlessly outfit your Pro Touring ride with race car technology in a way you can’t with simple retrofits on a stock chassis.
Starting at the front-end, there is a world of difference with the rack-and-pinion steering and suspension geometry. “The front suspension was originally based on circle track-style components and geometry,” Dale stated. “Over the years, we’ve optimized the parts to get the best ride quality using the best components, and have superior handling. The long front shocks used offer a great amount of suspension travel, which helps with ride quality. We fabricate our own spindles out of steel, so they’re very strong compared to a Mustang II spindle. It allows a little more flexibility in wheel choices, too; as a C6 brake kit has a lot of caliper overhang compared to ours.”
Of course, when you design the chassis from scratch, you can use any spindle or shock that you want, instead of being forced to utilize whatever shocks fits your OEM constraints. As such, Schwartz uses RideTech coilovers throughout. “RideTech utilizes shocks manufactured by Fox, a leader in shock manufacturing and technology. The basis around [its] shocks is they’re a monotube. A monotube shock has advantages over a twin-tube shock; one being they are often more predictable since the piston diameter is much larger. The shocks have adjustable valving, 24 clicks of adjustment. The single-adjustable shocks are great for 95% of muscle car builds. They can be softened for street use, or adjusted stiffer for track use. Oftentimes, a driver will reach their limit rather than the shock reaching its limit while racing. Once that shock limit is reached, then RideTech can do a triple-adjustable shock, which is more specifically-valved for the intended use.”
The two most noticeable adaptations of race car technology on the Schwartz chassis are the splined anti-roll bars and the floater rearend. “Our splined bars are manufactured by a leading NASCAR and circle-track supplier. They’re heat treated, which keeps them strong and have a consistent rate throughout use of the bar. They’re lighter weight than a typical bent bar. Since we use a completely different suspension and frame, we are able to fit this bar. A stock frame makes it harder to fit this type of bar into the constraints of the frame/steering setup,” Dale affirmed.
If you are wondering what a floating rearend can do for you, the simple explanation is: “The full-floater system prevents the axle shaft from moving around during hard side loads, which pushes the pistons back into a fixed-mount [brake] caliper.” Simply put: you can have a set of powerful, fixed brakes front and rear with none of the drawbacks. However, we’ll have more information on the Baer full floater we used on Project Payback on Street Muscle soon.
Built to Order & Made to Fit
When it comes to Pro Touring suspension, we live in unprecedented times. There is race car technology that you can mail order and have sent to your house. What sets the Schwartz Performance chassis apart is that it offers this technology and performance in a package that simply bolts up to your stock body. No floor cutting or fabrication is required for the chassis (your engine and transmission choice may be a different story), though a narrowed fuel tank is required since the rear frame is narrower for larger tires. These fuel tanks, as well as engines, transmissions, wheels, and tire packages–and even installation–are available at Schwartz Performance.
“The chassis uses all factory mounting points,” Dale stated. “These chassis are built to order, specifically for the customer and their build. If you told us ‘hey, I have a brand loyalty to X company for X part, can you use it?’ Depending on the part, we can usually accommodate. Powdercoat colors, power versus manual rack-and-pinion… Even the rearend; if a customer just wants a nice ride to and from the local cruise night and isn’t so hard on their car, they don’t necessarily need the added expense and advantage of a full-floater.”
Dale did provide a few bits of warning, though, with such a custom chassis: “The chassis is specifically built for your engine and trans combo. If you change your mind throughout the build, it may require different mounts.” In addition, the chassis does not use factory body mounts. “These bodies are old. They were built a long time ago, and had a large margin of error. If there are any varying points in the body-mount locations on the BODY, the STOCK FRAME makes up for it by flexing. Our chassis doesn’t flex. If the body has any different mounting heights, our chassis will tweak the body. Hence the reason to make your own mounts.”
So there you have it: four reasons we chose a Schwartz G-Machine chassis for our 1968 Pontiac GTO, aka Project Payback. If you are into Pro Touring, GTOs, or just GM A-bodies in general, please follow along and stay tuned for updates in the coming months.