Trask Assault Billet Aluminum Swingarm – Harley M8 Softail

Fits: '18-'24 Softail (Gen 1)

**Does not fit wide tire (240mm) applications.** 

The M8 Softail platform has become one of the best foundations for a serious performance Harley build.

So why stop at the motor, suspension, and controls?

The Trask Assault Swingarm for M8 Softail replaces the factory swingarm with a precision-machined billet T6061 aluminum assembly engineered to increase rigidity while reducing weight.

Its race-inspired, pocketed construction eliminates welded joints, while the included titanium axle and hardware take the weight-conscious design even further.

And despite looking anything but stock, it's designed as a 100% bolt-on factory replacement.

Billet aluminum. Titanium hardware. No welded joints. No half measures.

Why Upgrade the M8 Softail Swingarm?

Performance is a system. More power matters. Better suspension matters. Better brakes matter.

But all of those components still depend on the motorcycle's chassis to work together.

The Trask Assault Swingarm is designed to replace the factory M8 Softail swingarm with a lighter, more rigid billet aluminum structure developed around performance riding.

It's the kind of upgrade that makes sense when the goal isn't simply adding another part.

It's building a better overall motorcycle.

Precision Machined From Billet T6061 Aluminum

The Assault Swingarm is precision machined from billet T6061 aluminum.

Trask's race-inspired design focuses on two objectives:

• Increase rigidity. Significantly increases rigidity for a smooth and controlled ride through every corner.

• Reduce weight.Weight: Stock: 26.8 lbs - Trask: 20 lbs = 25% weight reduction

• Adjustable: Easily adjust the swingarm length up to 2” for enhanced control and stability during launches.

The result is a dramatically different approach from the factory swingarm and one that looks right at home on a high-end M8 Softail performance build.

No Welded Joints

Take a closer look at the Assault Swingarm and you'll notice something important.

Pocketed joints eliminate the need for welding.

Rather than relying on welded construction, Trask engineers the pocketed joints for maximum strength as part of the swingarm's modular billet design.

It's functional engineering that also gives the Assault its unmistakable machined appearance.

Titanium Axle & Hardware Included

Trask doesn't stop with the aluminum swingarm.

The Assault kit includes a titanium axle and titanium hardware, providing additional strength while contributing to the overall weight-saving approach of the assembly.

That makes the included axle and hardware an important part of the package—not an afterthought.

100% Bolt-On Factory Replacement

Something this serious looks like it should require an entire fabrication project.

It doesn't.

The Trask Assault is designed as a 100% bolt-on replacement for the factory M8 Softail swingarm, allowing it to integrate into the motorcycle without requiring custom fabrication to mount the swingarm itself.

That's a major advantage for riders building a high-level performance Softail without turning every upgrade into a one-off fabrication project.

Keep Your OEM Brake Caliper

The Assault Swingarm is designed to accept the OEM brake caliper using the supplied bracket.

That allows the factory braking component to integrate with the new swingarm rather than forcing an unnecessary caliper change simply to complete the installation.

New Spherical Bearings Included

The kit also includes new spherical bearings, providing the components necessary for the swingarm assembly rather than requiring you to reuse old bearings from the factory setup.

Raw Machined Finish

The Trask Assault Swingarm arrives unassembled in a raw machined finish.

And that's intentional.

It gives you the opportunity to finish the swingarm specifically for your build rather than paying for a finish you're going to remove anyway.

Black. Contrast finish. Custom anodizing. Or something completely different.

Your bike. Your finish.

IMPORTANT CUSTOM FINISHING INFORMATION

Trask recommends using caution when applying a custom finish to the Assault Swingarm.

Anodizing is recommended.

If powder coating the swingarm, use caution around mating surfaces.

Coating thickness on critical mating surfaces can interfere with proper assembly and fitment.

Make sure your finishing shop understands that this is a precision-machined motorcycle chassis component—not simply another decorative part being powder coated.

Running a Chain Drive?

There's an additional consideration for chain-drive conversions.

If converting your M8 Softail to a chain-drive system, a custom chain slider should be fitted to help prevent the chain from wearing against the swingarm.

CHAIN DRIVE NOTE

Do not run a chain-drive conversion without addressing chain-to-swingarm contact.

A properly fitted custom chain slider should be incorporated into the setup to protect the swingarm from chain wear.

Key Features

• Designed for Harley-Davidson M8 Softail applications

• Race-inspired performance design

• Precision machined from billet T6061 aluminum

• Designed to increase rigidity while reducing weight

• Pocketed joint construction

• No welded joints

• 100% bolt-on factory swingarm replacement

• Titanium axle included

• Titanium hardware included

• Accepts OEM brake caliper

• Brake caliper bracket included

• New spherical bearings included

• Raw machined aluminum finish

• Ships unassembled

• Ready for custom finishing

• Anodizing recommended

• Chain-drive conversions require a properly fitted custom chain slider

Built for Performance M8 Softails

The Assault Swingarm belongs on the kind of M8 Softail where every part has a purpose.

Think:

Trask Assault Swingarm
+
Performance Rear Shock
+
Upgraded Front Suspension
+
Steering Stabilizer
+
Performance Brakes
+
Performance Exhaust & Tuning

It's not about bolting on the most parts.

It's about building a chassis capable of complementing the power, suspension, and riding style of the rest of the motorcycle.

Professional Installation Recommended

The swingarm is a major structural and suspension component of the motorcycle.

Correct assembly, axle installation, drivetrain alignment, brake installation, suspension setup, fastener torque, clearances, and final inspection are critical.

Professional installation by a qualified motorcycle technician is recommended.

If you're converting the motorcycle to chain drive, make sure the required custom chain slider and chain clearance are addressed as part of the installation.

What's Included?

• Trask Assault M8 Softail Swingarm

• Titanium axle

• Titanium hardware

• OEM brake caliper bracket

• New spherical bearings

Swingarm arrives unassembled with a raw machined finish.