Ultimate Guide to Fabricated Spindles for Racing - Benefits, Design, and Install Tips

What is a Fabricated Spindle?

A fabricated spindle is a custom machined component used in the suspension system of high performance vehicles like race cars. It replaces the standard spindle found on production vehicles and allows for more adjustability and strength.

Why Choose a Fabricated Spindle?

There are several reasons why serious racers opt for a fabricated spindle over a factory part:

• Strength - A fabricated spindle is typically constructed from a solid billet of aircraft grade aluminum or steel rather than a casting. This makes it much stronger to handle the rigors of racing.
• Adjustability - Fabricated spindles allow for more flexibility in terms of setup geometry. Features like multiple mounting points for the steering arm, adjustable castor/camber, and customizable bolt holes enable racers to fine tune the suspension.
• Lightness - Fabricated parts can be machined to remove unnecessary material, creating a lighter component.
• Durability - The aircraft grade metals and quality manufacturing means fabricated spindles resist bending or cracking under hard racing use.
• Customization - Fabricated spindles can be machined to specification so they work with a particular vehicle and suspension package.

Types of Fabricated Spindles

There are a few main types of fabricated spindles used in racing applications:

Straight Spindle

The most common style, the straight spindle has a single axis design and is used in applications with limited suspension geometry changes. It allows some camber adjustment but no changes to steering geometry. Straight spindles work well for basic lowered street cars and entry level racers.

Drop Spindle

A drop spindle locates the lower ball joint and steering arm lower than the upper mount and hub. This lowers the suspension and provides increased camber gain for improved grip when cornering hard. Drop spindles are popular in dirt oval and high angle drifting setups.

Hub Spindle

Hub spindles integrate the hub bearing into the spindle itself, creating a rigid high strength component. The integrated hub bearing reduces component weight and eliminates flexibility between the hub and spindle. Hub spindles are common in hardcore racing classes like Formula Drift.

Splined Spindle

Splined spindles use a spline and adjuster sleeve arrangement that allows the spindle orientation to be varied. This enables major changes to steering geometry like altering kingpin inclination angle and scrub radius. Splined spindles provide the most adjustment flexibility but are complex and expensive.

Key Design Aspects

There are several important design factors to consider for a fabricated spindle:

Steering Arm Location

Placement of the steering arm relative to the ball joints has a major effect on bump steer characteristics. Bump steer refers to the change in toe angle of the front wheels during suspension travel. Theideal scenario is to have zero bump steer for consistent steering feel. Arm location also impacts Ackermann geometry.

Spindle Offset

Spindle offset or height refers to the vertical distance between the wheel centerline and the upper and lower ball joint locations. Increased offset helps lower the suspension and can improve camber gain for more grip when cornering.

Brake Caliper Mounting

Fabricated spindles allow mounting the brake calipers in an optimal position for the particular suspension setup. Common methods include top mount, front mount, rear mount or a centered dual mount style. This flexibility prevents caliper interference and ensures maximum brake performance.

Steering Axis Inclination

Also known as kingpin angle, SAI refers to the tilt of the steering axis down from vertical. Typical SAI values range from around 8-18 degrees depending on factors like vehicle weight balance. Higher SAI values promote steering feel and stability but limit responsiveness.

Spindle Diameter and Offset

The diameter and offset of the spindle where the wheel hub mounts is critical. Diameter handles wheel bearing loads while offset positions the wheel relative to the ball joints. These must be carefully engineered based on the vehicle, wheel, tire, and suspension geometry.

Fabricated Spindle Manufacturing

The fabrication process for a custom spindle involves several steps including:

Design and Engineering

The spindle is CAD designed to meet the specific suspension, wheel, and brake requirements. FEA analysis optimizes the design for strength, fatigue life, and weight targets.

Material Selection

Most spindles are machined from 6061 or 7075 billet aluminum. Some ultra high strength spindles use stainless steel or titanium. Exotic alloys like magnesium or chromoly are also possible but less common due to cost.

CNC Machining

CNC machining centers carve the spindle from the raw material billet into the engineered design. Precise tolerances and finishes are achieved through step-by-step tool paths programmed into the CNC.

Finishing Operations

The spindle goes through various finishing steps like CNC engraving of the logo, tapping bolt holes, chamfering sharp edges, and polishing. The parts are then inspected to ensure they meet specifications.

Coatings/Treatments

Optional specialty coatings like anodizing or Teflon impregnation can be applied for enhanced corrosion resistance and long term durability.

Installing a Fabricated Spindle

Installing a fabricated spindle involves removing the factory parts, assembling the new spindle, and properly setting the alignment. Here are the key steps:

Remove Existing Components

Use a coil spring compressor to unload the springs and struts. Then disassemble the hub, brake rotor, caliper and all steering/suspension parts from the OEM spindle. If re-using any parts, note original orientation and settings.

Assemble Spindle

Press in new wheel bearings and install seals. Bolt on the steering arm, strut mounts, and brake caliper mount in their required locations with proper torque specs. Grease bearings before final assembly.

Mount Spindle

Position the spindle onto the ball joints and install cotter pins. Torque all mounting bolts to spec. Re-install brake rotors, calipers, and coils springs/struts.

Set Alignment

With the weight of the car on the wheels, check and adjust camber, caster, and toe settings. An alignment rack is ideal for this but on car adjustments are also possible. Re-check all bolts after initial road testing.

With everything properly installed and aligned, the fabricated spindle is ready to take your suspension performance to the next level!

Conclusion

Fabricated spindles are an excellent upgrade for racers seeking increased strength, adjustability, and performance from their suspension systems. The ability to customize the design opens up possibilities not available with factory parts. However, they do require careful engineering and expert installation to realize their full benefits. Overall, fabricated spindles are one of the best upgrades for optimizing handling on a race car.

FAQs

What vehicles use a fabricated spindle?

Fabricated spindles are most commonly used on heavily modified vehicles for racing applications like drag racing, drifting, rally racing, and off-road racing. They are an upgrade over the factory spindle to handle the demands of racing.

What are the disadvantages of a fabricated spindle?

Potential disadvantages include higher cost compared to factory parts, more difficult installation, and the need for custom engineering and fabrication. If not properly designed or installed, performance could suffer.

How much camber can you get with a fabricated spindle?

It depends on the specific spindle design, but fabricated spindles allow far more static and dynamic camber adjustment than factory spindles. Over -5 degrees of static camber is possible, with additional camber gain on compression.

Do I need special tools to install a fabricated spindle?

You may need some specialty tools like a coil spring compressor, ball joint separator, and alignment equipment. But many fabricated spindles reuse standard hardware and can be installed with common hand tools.

Should I upgrade anything else when installing new spindles?

It's advisable to install new wheel bearings, ball joints, and alignment components when fitting new spindles. Consider upgrading brake calipers, rotors, and lines too for optimal performance.