Chevy Tri-Five Frames - How It Works

Chassis pros dissect the inner workings of aftermarket frames for Tri-Five Chevys

Stephen Kim Dec 29, 2010 0 Comment(s)
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Steve McClenon: When designing a new frame, you don’t have to do much to make it stronger than a stock unit from the ’50s and ’60s. Factory full-frames like those used in Tri-Fives and A-bodies are like wet noodles. They use open-channel ’rails and have very shoddy welds. It makes you wonder how they held together at all, but most people never even realize that since the frame is covered up by the body. In comparison, the frames we build use fully boxed tubing. Our frames are lighter and stronger than stock, but they also take up less space and offer more ground and exhaust clearance. Plus, the rear framerails have been narrowed to allow fitment of 345mm rear tires. One thing to keep in mind is that original Tri-Five frames are nearly 60 years old, so frames that are still in good shape aren’t common, which makes an aftermarket frame more appealing. Our frames are designed to retain all the factory suspension pickup points, and we offer a full line of control arms, springs, shocks, brakes, rearends, steering boxes, and sway bars to go along with them. They’re designed so that you won’t have to hack up the car to install one. Just drop your body onto one of our frames using the stock mounts, and you’re good to go. The improvement in stiffness will make a car feel like it has full ’cage in it.

GT Sport Chassis

Craig Morrison: Art Morrison’s GT Sport frames have several innovative features that can make a Tri-Five Chevy handle like an exotic sports car. We start with an all-new frame built from 2x4-inch rectangular steel tubing. Combined with crossbracing that’s strategically placed throughout the chassis, the result is a frame that’s significantly stiffer than stock. Revised suspension pickup points allow lowering the car 3 to 4 inches while retaining full suspension travel. The body can be lowered even more with our optional drop spindles. The control arms, spindles, coilovers, and sway bars included with our Tri-Five chassis have been designed to take full advantage of the all-new frame design. The control arm angles have been optimized to create an ideal camber curve, while minimizing the side scrub movement of the tires. Furthermore, the control arm angle increases antidive characteristics for improved stability under braking and a smoother ride.

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While factory Tri-Fives came with 2 degrees of positive caster, we set the angle at 5 degrees in our GT Sport chassis. This not only enhances straight-line stability, but it also increases the tire contact patch and optimizes weight distribution during cornering. Likewise, we positioned the steering rack so that the bumpsteer curve closely matches the camber and caster curves. This means that the car will track straightly even on uneven surfaces. Significant time was invested in dialing in the roll center as well. For the first 3 degrees of body roll, the roll center is maintained almost perfectly, and the rate of vertical movement is at a 1:1 ratio with the suspension movement. That’s just another way of saying that the car will remain very stable and predictable during acceleration, braking, and cornering.

When a customer orders up one of our Tri-Five chassis, they get a brand-new frame, tubular upper and lower control arms, lightweight spindles, Strange coilovers, and front and rear sway bars. In the rear, the stock leaf springs are replaced with a triangulated four-link suspension. This offers vast improvements in rearend control under acceleration and cornering. Moreover, eliminating the leaf springs in conjunction with narrowing the framerails frees up enough space for 345mm tires. A power steering rack and 9-inch rearend housing are included with our frames as well.

For the ultimate in flexibility, our Tri-Five frames are available with engine mounts for Mouse motors, big-blocks, and LS series small-blocks. The frame will also accommodate most GM automatic transmissions as well as Tremec and Richmond manuals. Another nice feature are passages built into the crossmembers that allow routing the exhaust through the frame to further improve ground clearance. This frame has been proven to produce 0.94 g in lateral acceleration on the skidpad with street tires.


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