Geo Storm Owners Page - Tuning - Suspension; Chassis Stiffening

Suspension - Chassis Stiffening

Strut Tower Brace (Front and Rear)

The strut tower brace is the most common and visible chassis brace, spanning across the top of thee engine compartment (and trunk) to create a structurally rigid connection between the upper suspension mounting points on the left and right side of the car. The weight of the vehicle is supported on the strut towers, where the spring rests against the chassis, and the stress on these points is significant. The logic behind this brace is solid. The engine compartment (and trunk) is open on top, and lacks a structure to keep it from flexing back and forth with the forces of the suspension moving up and down. Bridging between the two upper suspension mounting points with a rigid brace will prevent the unibody chassis (stamped sheet metal held together with spot welds), from flexing. This will prevent stress on those spot welds, and will also enhance handling and steering response, by restricting all of the movement to the suspension, where it is acted upon by the suspension, instead of being absorbed in chassis flex.
Look for strut braces which have two or more bolt positions on each end. Ideally, three or more. This will prevent the strut brace mounts from becoming their own source of flex. Mounting a brace via a single bolt (such as the common hammered-end and welded-L-bracket type from

Robie the Robot

Isuzuperformance

The Isuzuperformance offered strut braces for both front and rear of the Geo Storm. The front strut brace end plates mount to the strut towers have four bolt holes on each end and mount to all three studs from the upper strut mounts, or all four studs when used with four bolt camber plates. This forms a rigid connection to the suspension, and sandwiches the strut tower between the two brackets to further enhance the structure. The Isuzperformance front strut brace is also the only professional quality front strut brace with a low profile design to fit beneath the lower hood line of the Geo Storm and Isuzu sister car Coupes (Impulse, Gemini Coupe, Piazza, and Asuna Sunfire). The Japanese companies offered front braces that were taller, and fit only the Gemini Sedan. And the Japanese companies' rear strut brace fit the Sedan only, and they did not offer a rear strut brace for the Coupe.

Lower Cross Brace / Tie Brace

The mounting points for the lower control arms are another point that can benefit from bracing. The bottom of the engine compartment (and rear suspension) lacks direct structure between the left and right sides of the car, and this provides an opportunity for flex. Linking the mounting points at the bottom of the suspension will provide more of the same benefits as a strut tower brace does at the top: better steering response and handling.
At the front of the vehicle, a tie brace that connects the fore and aft mounting points of the front lower control arms, reduces flex and improves steering response.
The rear suspension is mounted to the car via a cross brace or sub frame assembly. But the lateral control arms are attached to this cross brace by cantilevered attachment bolt. The mounting bolt threads through one control arm, then through the cross member box beam, then through the other control arm, and a nut secures the assembly together. There is no rigid support point on the outside attachment points of the control arm bushing, and this provides the opportunity for flex. Linking across the front of the forward facing side, and back of the rear side of the control arms, with tie braces, significantly strengthens the rigidity of the rear suspension.

Isuzuperformance

Isuzuperformance made lower tie braces for the Geo Storm and Isuzu cars.

Gacchiri – Cowl Brace

Between the strut tower and the A pillar of the Geo Storm, nine (9) sheet metal body panels come together. These panels are secured in place with spot welds, and make up nine sources of flex in the front unibody structure. The previous generation R-Body car, the Isuzu I-Mark Lotus Suspension and Gemini JT0 Lotus and Irmscher cars, had a cowl brace linking the structure between the A pillar and the frame channel beside the strut tower. Cowl braces are not uncommon as original equipment on many cars, especially sport models. And the same brace, under a new name, “Gacchiri Brace”, is a popular upgrade for drifting, rally, and circuit track use. Aftermarket Gacchiri braces typically mount over the top of the door hinges, providing six secure bolting points, and require the addition of mounting points to the side of the frame channel beside the strut brace. The brace forms a triangle between the three mounting points, preventing movement of the strut tower and flexing between the strut tower and the A pillar.

Chassis Stiffening Foam – Unproven Benefit, Serious Draw Backs

No one has ever published any data on the exact amount of stiffness improvement that chassis stiffening foam provides. This is probably because the type of equipment needed to twist an automobile frame is available only to someone with a budget of a large multi-national corporation, like an automobile manufacturer. All of the marketing claims made by chassis foam vendors are open-floored, meaning they all claim "Up to..." or "As much as...". This type of wording allows the vendor to cite over inflated numbers that they know the product can not possibly deliver, because the statement means "This product will provide between ZERO improvement and the number provided in the text of this statement". And we all know that ZERO is most often the actual number whenever someone phrases their claim this way.
None of the companies making and selling chassis stiffening foam have easily recognizable names of known auto body suppliers. Notice that none of these products are made by 3M, SEM, Dupont, Sherwin Williams, PPG, or any of the other big names in paint and auto body. Certainly, if there were any benefit for chassis foam, all of these companies would have their own products on the market to compete in the market.
The tension and compression forces on a frame section are highest at the outer edge of the skin, and negligible in the middle. Look at somethign simple in building structure like an I-beam and notice that the material is used most at the top edge (compression) and the bottom edge (tension)(It needs only to resist up and down forces). The web joining the two together is just to keep them attached. Take that example to structures that are designed to resist not only up and down forces, but sideways forces, such as in an automobile. Look at a frame section and notice it is not solid, it is a tube. This is because all of the forces it must resist are at the edges, not in the middle. Unibody chassis design is based on folding pieces of sheet metal to form tubes around the perimeter of the passenger and mechanical compartments. Cylindrical shapes and folded edges enhance the strength of the tubes. And the larger the tube is made, the thinner the material required to provide a given stiffness and rigidity. The open area in the middle of the tube is not important to the stiffness of the tube. If it were, automakers would be making vehicles with solid 2 inch by 2 inch square bar in the A, B, and C Pillars and Rockers.
You may or may not be aware that there are several rather important electrical wires run through the Pillars and various frame channels of the vehicle. These wires include the rear window defroster, high mounted third brake light, radio antenna, dome light, door pin switches, and door speakers. Most of these wires transit from the body to the doors and hatch, or are mounted to the body, and have the electrical connector plugs located within the Pillars of the vehicle. Removing the doors or rear hatch, or servicing any of these electrical devices requires pulling the wiring harness through an access hole so that the wire can be unplugged for disassembly, or stuffing the connected wire back through the access hole into the Pillar for reassembly. If the pillar (frame channel) has been filled with foam, foam that is rigid enough to supposedly stiffen the chassis of the vehicle, then there is no way to access these electrical connectors in order to service these items.
In addition to this, should it be needed to either run an additional wire within the Pillars, or replace an original wire within the Pillar, this is impossible to do if the Pillar has been filled with foam.
The Rocker channel running along the right and left sides of the vehicle has drip holes. This is because the automaker knows that there will be water leakage into the chassis of the vehicle, and the automaker has provided a passage for that water to be evacuated from the vehicle, by running down the Pillars and out the drip holes in the Rockers. If the Pillars and Rockers are full of foam, there is no passage for the evacuation of water out of the vehicle chassis. The foam itself MAY OR MAY NOT absorb water like a giant sponge. If it does, then it will hold the water within the unibody chassis where it will cause extreme rust damage. If it does not hold water, it will cause the water to collect and puddle within the Pillars and Rockers. It will hold the water against the sides metal and prevent evaporation by the air within the frame channels, because that air has been displaced by foam. And the foam will impede the flow of water and block the drip holes where the water is meant to evacuate the vehicle.
In the event that the vehicle body must be repaired via welding, such as cutting out a rust hole and welding in a patch, the foam becomes a significant impediment to this. The foam may be described as "non-flammable", but expose just about anything to a fresh bead of molten steel, and it will burn. In order to make a repair weld, the foam will have to be removed from the immediate and adjacent area where it might be exposed to excessive heat.
The flexing in an automobile unibody frame occurs at the seams and connections between the sheets of stamped steel, not at the formed frame channels of the Pillars and the Rockers. These seams are along the edges of the floor pan, the fire wall, outer sides of the strut towers and front suspension structure, and wherever the one sheets of stamped steel is attached to another sheet of stamped steel. Foam inside of the frame channels does nothing to increase the rigidity of these seams. Only supplemental welding will accomplish this goal.

Spot Welding

Seam Welding / Stitch Welding

Seam welding provides for the same improved joint rigidity as spot welding discussed above. Seam welding is a little less subtle and easier to see. But seam welding can be done in areas that a spot welder will not reach. A good quality Mig welder is recommended. This is one situation where the quality of the tool has a large influence on the quality of the result, because a low quality welder will probably just blow holes through the thin sheet metal of the vehicle body, while a good quality machine will run beautiful weld beads.
Welding and Race Rules

Rules for racing classes with limited allowable modifications typically ban chassis reinforcing by welds. However, these same rules do not limit the thoroughness of body damage repairs. If it can be proven that the vehicle was in an accident and required frame repair, or that panels had to be replaced or repaired due to rust restoration, then just how zealously those repairs are performed is not outlined or restricted in the rules.

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