Top 5 Mistakes to Avoid When Building Your Custom LEGO MOC Cars

Building custom LEGO MOC cars can be an incredibly rewarding experience. Whether you’re a beginner or an experienced builder, there’s always room to improve your skills and avoid common mistakes that can impact the quality of your finished model. As fun as it is to dive straight into a build, knowing what to watch out for can save you time, frustration, and even money.

In this post, we’ll break down the top five mistakes to avoid when building your custom LEGO MOC cars, so you can enjoy a smooth and successful building process.

1. Skipping the Planning Phase

One of the most common mistakes builders make is diving into a MOC car build without proper planning. Custom LEGO MOC models are often more complex than official sets, so it's essential to understand the design, parts list, and building instructions before you start.

Take the time to thoroughly review the instructions, and ensure you have all the pieces laid out. Skipping this step can lead to frustration later on, especially if you find yourself missing a critical part in the middle of the build.

Tip: Organize your pieces by color and type before you begin. This will make it easier to find the parts you need as you work through the build.

2. Using the Wrong Pieces

When building a custom LEGO MOC car, accuracy is key. Using the wrong piece in a crucial step can throw off the entire build, resulting in structural issues or aesthetic problems. Custom MOC cars are often designed with specific parts in mind, and substituting pieces—whether intentionally or by mistake—can compromise the integrity of the final model.

For example, using a different type of axle or gear in our Bugatti Special Edition could affect how smoothly the wheels turn or how the suspension functions. Make sure to double-check the parts list and ensure you’re using the correct components throughout the build.

3. Ignoring Structural Stability

A common mistake for newer builders is focusing too much on the aesthetics and not enough on the structural stability of the model. While custom LEGO MOC cars are designed to look realistic, they still need to be sturdy enough to hold up under their own weight. Failing to reinforce key areas—such as the chassis or axles—can result in a model that’s prone to falling apart or losing functionality.

For instance, our Aston Martin DBRS9 GT3 features a robust frame that ensures durability, even during play or display. Pay close attention to these structural elements, as neglecting them can turn an otherwise beautiful build into a fragile one.

4. Overlooking the Importance of Instructions

Unlike official LEGO sets, which come with highly detailed and easy-to-follow instructions, custom LEGO MOC builds often require more focus and precision. Some MOC instructions may lack the clarity of official LEGO manuals, so it’s important to follow them closely to avoid mistakes.

Take your time, and don’t rush through the steps. Missing a single piece or skipping a step could mean having to disassemble parts of the model later, which can be frustrating. Following the instructions carefully will ensure a smoother building process and a more satisfying final product.

5. Forgetting to Plan for Display

After spending hours on a custom LEGO MOC car build, the last thing you want is to struggle with where or how to display it. Many builders overlook the importance of planning for display space, resulting in models that sit on a cluttered shelf or in an awkward location.

Think about how you want to showcase your finished model—whether it’s in a glass display case, on a dedicated shelf, or even as part of a larger collection.

Tip: Make sure the display area is stable and free from dust or direct sunlight, which can damage the bricks over time.

Conclusion: Build Smart and Enjoy the Process

Building custom LEGO MOC cars is a rewarding experience, but it’s easy to make mistakes if you’re not careful. By avoiding these common pitfalls—like skipping the planning phase, using the wrong parts, or neglecting structural stability—you can ensure a successful build from start to finish.

Looking for your next custom LEGO MOC car project? Check out our collection of sets and get started on your next dream build today!