Unlock Next-Level Performance:

Harley-Davidson Motorcycles are more than just machines; they're statements of identity, freedom, and raw power. For many riders, the journey doesn't stop at stock. Whether it's to boost horsepower, sharpen handling, or create a personal ride, performance upgrades are often the next step. 

From seasoned mechanics to first-time customers, more and more Harley owners are diving into performance mods for Harley-Davidson bikes to push limits and elevate the riding experience.

Why the urge to upgrade? It's simple: it adds style, and better performance means a better ride. Whether you're after smoother acceleration, more torque on the highway, or a deeper, throatier exhaust note, upgrades can completely transform how your Harley behaves and feels.

At Legendary Parts, we cater to both sides of the garage. Our extensive catalogue includes OEM parts that maintain factory specs and Harley-Davidson aftermarket parts built to unlock next-level performance.

Check out our full OEM & aftermarket Harley parts collection to find the perfect fit for your build.

However, that raises a significant question: Which OEM or aftermarket motorcycle parts deliver the best results? The answer depends on your riding goals, budget, and vision. In the sections, we'll discuss the comparison and key considerations to help you make the right call for your Harley.

OEM vs. Aftermarket Harley Performance Parts – Key Differences

Original Equipment Manufacturer: Parts are made by Harley-Davidson or their authorised suppliers. These components are identical to those originally supplied with your bike, designed to maintain factory specifications and meet the brand's rigorous standards.

Pros of OEM Harley performance parts:

• Designed to match your original bike specs.
• Consistent availability through official channels.
• Supported by Harley's parts system for documentation and servicing.

Cons:

• Performance gains are moderate and within factory-safe limits.
• Usually more expensive than aftermarket parts
• Not continually optimised for pushing performance boundaries

If you’re looking for performance upgrades for your Harley, explore our complete OEM Harley parts collection at Legendary Parts.

What Are Aftermarket Harley Performance Parts?

Third-party manufacturers create aftermarket parts designed to fit Harley models. These parts sometimes offer more aggressive tuning or personalisation options than OEM parts.

Pros of Harley-Davidson aftermarket parts:

• A wider selection of custom Harley modifications
• Enhanced performance potential (e.g., big bore kits for Harley-Davidson)
• Enables significant performance upgrades, such as big-bore kits, tuners, or exhaust systems.

Cons

• Research may be required to ensure fitment and compatibility.
• Fitment and compatibility may vary depending on the brand and model.
• Performance gains can vary widely depending on brand and tuning; some parts may prioritize aesthetics over horsepower. 

Best Harley Performance Upgrades: OEM vs. Aftermarket Comparison

Engine Performance Upgrades:

Regarding Harley engine upgrades, both OEM and aftermarket paths offer compelling options. OEM upgrades, such as the Screamin' Eagle performance parts, are factory-approved kits that integrate seamlessly with your existing setup. They're ideal for riders who want more power while staying aligned with Harley's recommended specs.

Among the well-known brands, only S&S offers Big Bore kits. ThunderMax, on the other hand, only provides modules for tuning and mapping optimization. These kits are popular among riders seeking a noticeable increase in Harley-Davidson horsepower.

For those looking to take it a step further, Stage 2 upgrades are a common next move. This stage involves replacing the stock camshaft with a performance camshaft, which can deliver a significant boost in power or torque, depending on the selected cam profile.

Well-known manufacturers such as S&S, Andrews, and Feuling offer a wide range of performance camshafts tailored to various riding styles and engine setups. These brands are trusted in the Harley community for their precision engineering and deep understanding of V-Twin performance.

When properly installed and tuned, Stage 2 upgrades can dramatically transform your riding experience.

Exhaust Upgrades

OEM Harley exhaust upgrades, such as the Screamin' Eagle exhaust system, are engineered to meet sound and emission standards, making them a solid choice for riders looking for a controlled but slightly enhanced tone.

In contrast, aftermarket Harley exhaust options from Vance & Hines or Bassani deliver deeper sound profiles and can contribute to improved airflow. The aftermarket route offers more variety if looking for the best Harley pipes to enhance style and performance.

Air Intake & Fuel Management

For those tuning their fuel system, Harley-Davidson performance air intake systems, such as Screamin’ Eagle high-flow air filters, offer OEM-approved enhancements.

Aftermarket alternatives, such as K&N air filters and fuel tuning tools like the DynoJet Power Commander, provide more control for riders customizing their airflow and fuel mapping. These tools support Harley tuning and remapping, particularly with other engine and exhaust upgrades.

Suspension & Handling Upgrades:

Harley-Davidson suspension upgrades improve handling while preserving the bike's original geometry. Depending on the setup, they enhance either dynamic performance or riding comfort.

Upgrading rear shocks or fork springs doesn't alter the frame geometry; it simply enhances the ride, making it sportier or more comfortable, depending on the setup. You only start adjusting the bike's geometry when you install raked triple trees, and that's more about custom style than performance.

However, aftermarket solutions like Progressive Suspension or Öhlins shocks offer a wider range of adjustments, making them perfect for riders seeking a more personalized feel or improved handling on long-distance rides. Harley catalogue suspension upgrades improve handling, while OEM suspension maintains the bike’s original handling characteristics.

Which Performance Upgrades Are Best for Your Harley?

Factors to Consider:

When deciding between OEM and aftermarket performance upgrades for your Harley-Davidson, several factors come into play:

Budget:

Like Harley’s Screamin’ Eagle components, OEM parts tend to be more expensive due to brand reputation and compatibility. Aftermarket alternatives, like S&S or Vance & Hines, often offer a wider price range, making them appealing to budget-conscious riders. However, cost shouldn't be the only consideration.

Riding Style (Touring, Street, Racing):

Your typical riding environment should influence your choices. Touring riders may prioritize comfort and reliability—areas where OEM upgrades shine. Street and racing enthusiasts might prefer aftermarket parts that push limits with enhanced horsepower, torque, and customization options.

Installation Difficulty:

Thanks to factory specifications and dealer support, OEM parts are usually easier to install. In contrast, some high-performance aftermarket components may require professional installation or tuning, which can add to the total costs and time.

Balancing these factors helps you choose the right upgrade path aligned with your goals and riding habits.

How to Choose the Best Performance Parts for Your Harley

Upgrading your Harley-Davidson is a thrilling journey, but to get the most out of your performance parts, it’s essential to choose wisely. Whether you're chasing more horsepower, better handling, or improved style, here’s a quick guide to making smart upgrade decisions.

Research Reputable Brands

Start with well-known names in the Harley world. Brands like Screamin’ Eagle (OEM), S&S, Performance Machine, Vance & Hines, and Roland Sands are trusted for their innovation and reliability. These are among the best Harley-performance brands for both engine and aesthetic upgrades. Legendary Parts offers a curated selection of OEM and aftermarket parts from the top brands in the industry.

Read Customer Reviews

Real rider experiences can reveal much about how a part performs on the road. Look for consistent positive feedback around installation, performance gains, and longevity. Our product listings at Legendary Parts feature verified reviews from Harley owners across Europe to help you decide.

Check Compatibility With Your Harley Model

Not all parts fit every model. Before buying, double-check compatibility for your specific Harley year and trim. Legendary Parts simplifies this with detailed compatibility info on every product page, so you’re not left guessing.

Legendary Parts makes it easy to upgrade with confidence. Whether you want genuine Harley parts or bold aftermarket mods, we've got the aftermarket Harley parts guide and product range to match.

Shop Harley performance upgrades at Legendary Parts today.

Final Verdict – Best Performance Parts for Your Harley

When upgrading your Harley-Davidson, the choice between OEM and aftermarket parts ultimately depends on your goal.

OEM parts are built to Harley-Davidson's exact specifications, tested for fit and performance, and ideal for riders who want to maintain stock performance. 

On the other hand, aftermarket parts unlock more power, sound, and style. Whether chasing horsepower gains, a unique exhaust note, or custom aesthetics, the aftermarket world gives you more flexibility.

So, how do you decide?

Choose based on your riding goals and budget. For a plug-and-play advantage, stick with OEM. If you desire top-end performance or a personalized look, well-chosen aftermarket parts may be your best bet.

Our expert-curated selection makes the decision easier. Whether you need OEM reliability or aftermarket performance, we've got you covered.

Find your perfect Harley performance parts at Legendary Parts and upgrade your ride today!