sorry if someone already said this but do y’all think with essek being a part of the teaser. we’re gonna see his beacon shenanigans happening concurrently w early m9 shenanigans.

A CNC Designed, Off-The-Shelf Custom Chassis for 1973-1987 C10s

When I first met Phil, Neal, and Jeremy Gerber back in the early aughts, the guys were still cutting their teeth in a small shop in Elgin, Illinois, building chassis for many an early Ford, among others. Fast-forward some 15 years and the guys have grown their little shop into one of the biggest in the business with a laundry list of accolades to boot. Yet while the business grew and the shop got larger, they didn’t simply set their sights on continuing the expansion within their existing catalog. Instead they concentrated on integrating advanced technology to both their manufacturing and engineering sides of the business in order to not only improve upon their existing line but to also grow into segments where their business had not once existed. Gone are the days where chassis are fabricated using multiple sheets cut from templates to create boxed framerails and the like. Today, Roadster Shop uses CNC-based technologies to design and manufacture chassis that are lighter, stronger, and easier to assemble than those of the past. This allows the crew to design a chassis with a specific goal in mind, as opposed to having to modify an existing design to do something which it was never meant to do. But more importantly, this streamlined approach to frame manufacturing results in a lower cost product without sacrifice.

Enter Roadster Shop’s new SPEC-series chassis. Using the aforementioned latest techniques in manufacturing, the SPEC-series chassis are assembled using Roadster Shop’s exclusive CNC laser cut framerails contoured and joined using a series of interlocking keys and slots that, once formed to shape, ensure proper alignment of the frame sections and provide for a consistent welding gap. This procedure not only speeds up manufacturing but results in a stronger, lighter chassis with no kinks, bends, or stressed areas that are prone to flex.

But Roadster Shop’s engineering department didn’t stop there. As we mentioned before, the guys had a particular goal in mind when it came time to design a new C10 chassis and that goal was to get things low. And yet while a pair of dropped spindles and shocks, a couple lowering blocks, or a set of airbags could have done the trick, the boys know all too well that those results often leave other, less desirable results to linger. Lowering a stock-style chassis can result in a ride height where the suspension components were not originally designed to function, putting increased stress on items such as ball joints, shock mounts, and tie rods. Bumpsteer and incorrect camber and alignment situations are also common problems on extremely low applications. The crew was well aware of this, designing the one-off IFS and rear suspension system of their SPEC chassis for the ultralow crowd. With stepped framerails, front and rear, Roadster Shop designed their new SPEC chassis for an aggressive 4.5/5-inch raked ride height, whether equipped with airbags or coilover springs. Equipped with ride height adjustable airbags, this allows the chassis to lay rocker, putting the pinch weld of the truck’s body literally in the weeds.

With the height requirements set in stone, or rather programmed into their CAD program, the engineers at Roadster Shop set out to design a double-wishbone IFS setup using in-house fabricated upper and lower control arms mated to Wilwood Pro Spindles. Eccentric adjusters are utilized on the upper control arms to make alignment adjustments quick, easy, and accurate. Sprung options include an airbag setup or a more traditional coilover shock. A front-mounted power rack-and-pinion and aggressive sway bar ensures the function of the front end reflects the form. Out back, a parallel four-bar setup is utilized, mated to a 9-inch Ford rearend housing. Both upper and lower four-bars are poly bushed, while the heavy-duty lower four-bar features eccentric mounting to make wheelbase and pinion angle adjustments quick, easy, and accurate, just like the front upper control arms. And like the front suspension, the guys designed the rear to perform just as well as it looked, with the allowance of a 12-inch-wide wheel equipped with a 345-series rear tire.

If all of this sounds good to you, we thought the same when the time came to start daydreaming our latest 1980 Chevy C10 build into existence. We knew we wanted to build something that could put those high and mighty muscle car guys in check and that it would require more might than, well, muscle. While the Supercharged LT1 we had hidden away in the tech center should be more than enough to power our square-body, we wanted to be certain that the backbone of our C10 could effectively put the power to the pavement. Given the background on what Roadster Shop guys put together in the form of their SPEC-series chassis, I’m feeling pretty confident that it will live up to our every expectation.

Here’s Roadster Shop co-owner Phil Gerber’s square-body sitting on its rockers, evidence of how low their SPEC chassis is spec’d to sit when equipped with an airbag setup at all four corners.

Stripped to the bare essentials, the details of Gerber’s chassis emerge. Note the kickup in the framerails, which combined with the airbag suspension, allows the truck to lay the rockers in the weeds, if so desired.

This illustration shows in detail the articulation of the suspension components at ride height versus fully compressed.

Our SPEC chassis, fresh from a bath in the powdercoating booth at Eddie Motorsports, is ready for final assembly. While Gerber’s chassis was equipped with airbags to get it down low, we opted to go with a coilover setup to keep things simple. Even so, the geometry of the SPEC chassis is good for a 4.5/5-inch final ride height.

After installing the Polyurethane bushings and pressing in the Moog ball joints, the control arms are ready to be bolted up to the chassis. First, the lower control arm is slid in place. Note the boxed design, which reduces flex and provides a solid foundation for the coilover shock to mount.

The upper control arm is another fabricated piece, though of a more industry standard tubular design, and mounts via two eccentric fasteners, designed to make alignment adjustments quick, easy, and accurate.

A Wilwood Pro Spindle comes as standard fare on all Roadster Shop SPEC series chassis, giving the end user a variety of options for brake components.

With the coilover shock and spindle in place and buttoned down, the front end is starting to come together.

Out back, the upper and lower parallel four-bars are installed on their brackets and torqued to spec. Note the beefy lower four-bars and the triangulated design of the system, which negates the need for a Panhard rod to keep the rearend centered.

Roadster Shop ships their SPEC chassis with a 9-inch Ford rearend housing and a pair of 31-spline axles. All that’s necessary to finish the rearend appointments are a ring-and-pinion, differential, yoke, and third-member housing.

We ordered an assembled third-member from Summit Racing (PN CUR-9TT370S) to fill our empty housing. One of the reasons the 9-inch Ford rearend is so popular in the aftermarket is the fact that the third-member can be removed and installed as a complete unit. This makes installation easy since the pinion preload, backlash, and torque have all been prefigured. We opted for a 3.70:1 gear ratio since we anticipate running an overdrive trans in our C10 mated to an Eaton Detroit Truetrac differential. The Truetrac is a helical-gear style performance differential that maximizes wheel traction by operating as a standard or open differential under normal driving conditions, allowing one wheel to spin faster or slower as necessary. This allows it to operate as an open differential until a loss of traction scenario occurs, in which the helical-shaped gears transfer the torque to the high traction wheel. These gears mesh with increasing force until the wheel spin is eliminated. This operation is smooth, quiet, and automatic with no wearable parts and no required maintenance, unlike posi units of the past.

With the rearend partially assembled, all that’s left is to slide the 31-spline axles in place. We’re going to wait on that until next month when we install the big Baer disc brakes at all four corners as the e-brake/caliper brackets retain the axles. This angle shows the double-adjustable AFCO shock and the eccentric adjuster that the lower four-bar utilizes, which allows for quick, easy, and accurate wheelbase and pinion angle adjustments to be made.

We couldn’t wait to get the chassis rolling, so we skipped ahead and installed the 14-inch Baer disc brakes and slapped on a set of rollers to see how the chassis looked on the ground. Note the beefy front sway bar and front-mounted power rack-and-pinion unit. We’ll take a closer look at the brakes next month, for now consider this a teaser of things to come.

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