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Chassis Heeltoe Explains

About Chassis Braces

Chassis bracing may be the most under-rated and misunderstood modifications available to a vehicle. If the chassis accounts for the frame, steering, and suspension pick-up points; then this assembly must be as rigid as practical to perform at its best. Some compliance in the chassis helps dampen noise, vibration, and harshness (NVH), and it is not possible to completely eliminate flex. However, using strategic pick-up points, aftermarket chassis braces can be very effective at enhancing the feel of steering and suspension systems, greatly improving driver confidence and, as a byproduct, speed.

Strength

Bracing works by resisting the forces of compression and tension. Keeping two points at a fixed distance apart is the goal. With a rigid mounting between them, two points cannot bend toward each other. Judging a brace by its assembly* or how heavy it is may not be giving credit to the actual function of the part.

Materials

Braces are most commonly made out of steel or aluminum. These materials are inexpensive and strong. Aluminum has a lower weight, but fabricating it to be effective does carry a higher cost than a steel part. The most intricate parts of braces are the mounting points. Some manufacturers will, therefore, use steel for the mounting points and aluminum for the joining bar stock, and attach them with bolts. Carbon fiber and titanium are other materials chosen for their lightweight and strength, in the face of their expense.

Construction

Braces made out of one piece, or being a welded-up assembly, are assumed to be stronger than those made of multiple pieces. This statement is a risky one because it is taking design and quality out of the picture. A well-designed brace made with quality materials that bolts together would be preferable to a cheap, flexible brace made to be one-piece. It is generally true that brace which is installed as one piece would be more rigid, but unless the brace is then welded to the chassis itself, this point is largely irrelevant if the brace made is of high quality.

Placement

In general, bars mounted laterally (side-to-side) are effective at reducing twist in the chassis. Twisting movements cause the center points of the frame to move closer together. By fixing these points, the twist is resisted. Also, subframes and uni-bodies are made to accommodate the installation and mounting of other vehicle systems (exhausts, suspension parts, and drivetrain assembly) and closing these open areas “boxes” them in making the entire chassis stronger in that area. Lateral bracing will be felt more in turns where there is a high load.

Longitudinal braces help resist bending in the chassis as the front and rear traverse bumps in the road. The front and rear work together more than most would assume. By simply going over a bump, the chassis will bend, and in these bending moments, there is a numbness that reduces confidence. It’s not as apparent at road-speeds, but at highway or HPDE speeds, confidence is very important. Also, keeping the chassis flat reduces unwanted changes in wheelbase that can make the vehicle hard to set in turns after high-braking zones.

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Chassis Heeltoe Explains

What is the “Chassis?”

When speaking about the vehicle as a whole, the chassis is the first major component that is considered. The frame or unibody is the large structural unit that is the base of the vehicle’s assembly. The wheels, suspension, body, engine, and other vital parts of a vehicle all must attach to a base assembly; referred to collectively as the chassis.

Rolling Chassis

There are differing opinions as to what is included in a rolling chassis. Some sources include an engine and drivetrain nestled within an otherwise bare vehicle frame. Others claim a rolling chassis is more of a complete vehicle without the drivetrain; which is not accurate as a rolling chassis would not necessarily include any coachwork or comfort items. Body-on-frame cars are easier to visualize as a rolling chassis; it’s the vehicle with the body removed. An engine need not be part of the package as long as the suspension arms, dampers, springs, and hubs are there, along with brakes and wheels.

Chassis versus Frame

To state a chassis as “the frame” may be an over-simplification of what a chassis is. The frame is the major component of the chassis; it acts like a skeleton that provides the backbone of the vehicle. To it, suspension arms with spindles, brakes and wheels are attached. As components are added, the frame becomes a chassis. To put it another way, the chassis is the pure functional component assembly without the body on it.

Chassis versus Shell

It becomes difficult to nail down where the chassis stops and the body starts when the vehicle has a uni-body construction. In these chassis configurations, the body shell serves as the frame. As such it is not practical to visualize the frame without the body. With the aid of auxiliary sub-frames that are affixed to the uni-body, suspension arms are attached to the body, to create a rolling chassis. Commonly, people will refer to this chassis as a shell or a rolling shell. While the body is present, the interior usually would not be. Again, the powertrain is “optional.”

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Chassis Heeltoe Explains You Can Do It! DIYs

Spoon Rigid Collar Bushing Reuse: Are They One Time Use?

The Spoon Rigid Collar Bushings are great pieces for ensuring subframe-to-chassis alignment is correct. If you are not familiar with these awesome bushings, please see a very informative video in this post explaining what they are and how they work.

Here is what the Spoon Rigid Collar Bushing kit looks like:

In a nutshell, the Spoon Rigid Collar Bushings slide over the bolt and deform to fill the tolerance to the bolt hole.

Subframe bolt hole diameter versus bolt diameter.

The irregular mating surface between the subframe and chassis is made more rigid which really does dramatically improve the chassis feel.

Spoon Rigid Collars Bushings deform to fill tolerance between the subframe, chassis, and bolts.

The question of the day is, once these rigid collars are installed and deformed, do they need to be replaced if the subframe comes out again?

Heeltoe’s answer is no, these areĀ notĀ one-time use bushings. We have in our own shop #HTSpecTSX removed the subframe twice after initial installation, with plenty of driving stints in between removals. Our observation was that while the bolts are decidedly more finicky to remove and replace after the bushings are in, and that subframe re-installation alignment is more challenging because the bushings are in place, theĀ re-installation of the subframe had gone without issue.

Indeed the additional effort needed to remove and install the subframe, while not excessive by any means, proved that the collars worked and did their job.

No degradation of the effect of the bushings was noted after repeated removal and reassembly.

That being said, we would NOT recommend attempting to remove deformed bushings from one car to install them on another, even of the same model. Once a Spoon Rigid Collar Bushing set is deformed on a specific chassis and subframe we feel this “mates” these items all together and that attempts to move used bushings from one car to another would be an unsuccessful job.

On a final note, Heeltoe DOES recommend that the suspension alignment be adjusted after subframe removal, even with the bushings in place.