On the track, performance is measured down to hundredths or thousandths of a second. The difference between first and placing off the podium could be the blink of an eye. Every last drop of performance counts, and one way to optimize performance is to optimize the vehicle’s camber.
There are several ways to adjust camber, including the use of control arms with offset bushings. It’s usually easier to remain compliant with track rules using this approach, so offset bushings are a popular option for racers.
Some expert manufacturers produce a variety of control arms with offset bushings already installed. It’s a precision-minded process, and here’s how it’s done.
The Offset Bushing Seating Process
Ideally every control arm is fitted with offset bushings that are individually seated by our technicians. A hydraulic press supplies the seating power, but skilled hands supply the fine adjustments needed to get that perfect fit. Here’s what the process entails:
- A spacer block is placed inside the control arm body, between where the bushings will go. This block stabilizes the body during pressing and ensures the arm’s “spokes” aren’t warped while under intense pressing pressure.
Expert manufacturers have a collection of spacer blocks for a variety of racing vehicles, so the right block can be matched to the right vehicle model. - The bushings are fitted onto the press’s jig using alignment pin holes already drilled into each bushing. The bushings maintain their position during pressing due to the tight fit, but a few taps with a rubber mallet ensures an even tighter, and better fit.
- The spacer block and control arm are placed inside the hydraulic press and aligned with the bushings.
- As soon as the bushings enter the control arm, the press is shut off. At this point, the bushings have not been fully seated, but have been seated enough that the technician can make adjustments to the control arm without losing alignment.
- The most important adjustment is to the control arm’s vertical center line. To ensure the most precise result, a laser level should be used to make the adjustment. This isn’t a major adjustment – a few degrees off the center line is sufficient.
- Once the ideal center line is established, the press is powered on again and the bushings are completely seated.
At this point, the offset bushings are fully seated, but there’s still another step before they’re ready for use.
A Couple of Additional Control Arm Quality Improvements
This offset bushing seating process is precise and reliable, which means reliable performance on the track. However, the seating process is only one factor behind control arm performance. There are additional quality-related improvements that can be made, including:
- The use of a flange in the inner sleeve – Offset bushings may be fitted with a flange that sits inside the bushing’s inner sleeve. The flange reinforces the bushing and also provides an expanded contact surface between the inner sleeve and the subframe. This expanded contact surface spreads the load out and prevents the inner sleeve from digging into the subframe. The flange is threaded onto the long bolt that slots into both control arm bushings, so it remains secure even after the control arm is bolted to the chassis.
- The post-seating milling process – Because these bushings are offset, they have a tendency to go a bit egg-shaped following pressing. This is most noticeable where the bushing holes are drilled, and if not corrected, the very slight warping will reduce clearance and produce a suboptimal fit.
A detail-oriented manufacturer will pass the bushing through a final milling step before it can be installed on a racing vehicle. During milling, the bushing hole is reamed out using a dedicated reaming tool that has a guide bushing on it. This process leaves the bushing with ideal clearance for an ideal slip fit.
ApexPAI is the Material of Choice for High Quality Control Arms
High quality control arms are manufactured using ApexPAI as the primary material. ApexPAI is a proprietary grade of polyamide-imide (PAI) that’s purpose-made for high performance applications. In fact, ApexPAI is the highest performing material for low friction bearings and bushings.
ApexPAI possesses the same impressive qualities of other PAI grades, many of which are in widespread use in aerospace, semiconductor, defense, energy, and other extreme applications. A few of ApexPAI’s advantages include:
- Unsurpassed durability and tribological performance – No non-metal offers the same degree of impact, tensile and compressive strength that ApexPAI does. PAI is also prized for its superior wear characteristics, which are present even when elevated temperatures are also present.
- Excellent processability – PAI is recognized as the best performing thermoplastic that can still be melt-processed. ApexPAI also offers good machinability, so it can be formed and shaped to a nearly endless degree.
- Excellent chemical resistance – ApexPAI can withstand chemical attack from a large variety of sources, including hydrocarbons and acids.
- Excellent thermal stability – PAI maintains its dimensional stability and strength even at extreme temperatures. At 400 degrees Fahrenheit, ApexPAI is stronger than most other engineering polymers at room temperatures.
A Superior Process and Superior Materials Make a Superior Control Arm
Non-metallic racing components that offer comparable (or superior) performance to their metallic counterparts are possible. Racing enthusiasts shouldn’t have to compromise chassis feedback or wear performance with a non-metallic alternative, and ApexPAI offset bushings ensure that compromise isn’t required.