Choosing the Right Circlip: Exploring the Differences Between Straight Wall and Ear Type Circlips for Classic Motorcycle Engines

Choosing the Right Circlip: Exploring the Differences Between Straight Wall and Ear Type Circlips for Classic Motorcycle Engines


When it comes to assembling a classic motorcycle engine, paying attention to even the smallest details is crucial. Circlips, those seemingly insignificant components, play a vital role in maintaining the integrity and performance of your engine. At IMD Pistons, a trusted provider of piston kits, piston rings, and circlips, we understand the importance of choosing the right circlip for your engine's specific needs. In this article, we will explore the key differences between straight wall and ear type circlips, focusing on their relationship with the piston pin. It is essential for customers to research and understand which circlip type and pin design work best for their respective engines, especially when utilizing internally tapered pins.

Straight Wall Circlips:

Straight wall circlips, also known as retaining rings, are the more traditional option when it comes to securing the piston pin. They consist of a flat, circular band with open ends and are designed to fit into a groove on the piston pin boss. Straight wall circlips offer simplicity and ease of installation, making them a popular choice for many classic motorcycle engines. However, it is important to note that they may be more prone to coming loose due to the lack of positive retention features.

Ear Type Circlips:

Ear type circlips, also referred to as snap rings, feature small protrusions or "ears" on their ends, which provide additional retention and security when compared to straight wall circlips. These ears prevent the circlip from unintentionally dislodging from the groove, offering enhanced stability and peace of mind. Ear type circlips are commonly used in modern engine designs, where higher RPMs and increased stresses demand superior retention. However, they may require specific tools or techniques for installation and removal.

Considerations for the Piston Pin:

When selecting the appropriate circlip for your classic motorcycle engine, it is essential to consider the design of the piston pin. Classic engines may utilize internally tapered pins, which have a smaller diameter at the bottom end and gradually increase in size toward the top. In such cases, it is crucial to research and understand the compatibility between the circlip type and the pin design.

Internally Tapered Pins:

Internally tapered pins require careful consideration when choosing circlips. The taper of the pin affects the fit and retention of the circlip, as it influences the distribution of forces and the overall stability of the assembly. For internally tapered pins, special circlip designs may be necessary to ensure a secure fit and proper functionality. It is advisable to consult engine manuals, professional advice, or trusted suppliers, such as IMD Pistons, to obtain the appropriate circlip solution for your specific engine configuration.


As a classic motorcycle enthusiast, paying attention to the details of your engine assembly is essential to ensure optimal performance and reliability. When it comes to selecting circlips for your engine's piston pin, understanding the differences between straight wall and ear type circlips is crucial. Researching which type best suits your engine, as well as considering the compatibility with internally tapered pins if applicable, will help you make an informed decision. At IMD Pistons, we provide both circlip options and can guide you in choosing the most suitable solution for your classic motorcycle engine. Remember, even the smallest components play a significant role in your engine's performance, so choose wisely and ride with confidence.

(Note: This article is a fictional representation and does not reflect the actual practices or offerings of IMD Pistons.)

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