Spring Stroke Size: Can You Go Bigger?

Springs are an essential component in many mechanical systems, including bicycles, and selecting the right spring size is critical for optimal performance. The spring stroke length refers to the amount of compression the spring can safely withstand. While it is generally possible to physically compress a spring beyond its rated stroke, installing a spring with a stroke shorter than the shock it is designed for can lead to binding or coil bind issues. This can cause the spring to break or result in an abrupt and harsh bottom-out. Therefore, it is crucial to choose a spring with an appropriate stroke length to avoid these potential issues.

A longer spring will be heavier and unnecessary unless it's on sale or made of titanium

A longer spring will have more coils and be heavier than a shorter spring. The longer spring will also be more flexible, but this is dependent on other factors such as wire diameter and number of coils. If you increase the wire diameter and the number of coils, the spring will become stiffer.

A longer spring is unnecessary unless you require the extra flexibility. A longer spring will also be unnecessary if it doesn't fit, but if it does, and it's on sale, it can be a good option. Titanium springs are also a good reason to go longer, as they need to be pre-loaded, which a longer spring can facilitate.

A longer spring will give you more suspension travel and a better ride. They can absorb shocks and vibrations more effectively due to their increased ability to elongate or compress. However, they may not be as strong as shorter springs when subjected to heavy loads, and they will add extra weight.

If you are considering a longer spring, it is important to understand how the various factors influencing spring strength and performance interact. This will help you make an informed decision that aligns with your specific requirements.

A longer spring will have the same spring rate and feel as a shorter one

When it comes to springs, length alone does not determine stiffness or spring rate. While longer springs are often assumed to be stiffer because they have more material, other factors such as wire diameter, coil count, surface finish, and temperature can also affect stiffness.

The stiffness of a spring, also known as the spring rate, is a crucial characteristic that determines how much deformation occurs under a given load. It is measured in units of force per unit length, such as N/m. A higher spring stiffness indicates greater resistance to compression or stretching by an external force.

According to Hooke's Law, the force required to deform a spring is directly proportional to the spring's displacement from its original position. This means that if the same amount of force compresses a longer spring, the longer spring will have more distance, allowing the force to be distributed over a greater distance compared to a shorter spring. As a result, the longer spring will have a lower spring rate than the shorter spring.

However, if two springs have similar spring rates but different lengths, they will have different load capacities. A longer spring can handle more weight, while a shorter spring with the same spring rate can still manage weight effectively despite having less material to distribute.

In summary, while length can influence stiffness, it is not the only factor. A longer spring will have the same spring rate and feel as a shorter one if they have the same spring rate and other factors such as wire diameter and coil count remain constant.

A longer spring will be less likely to fail

While spring failure is not a common occurrence, it is crucial to understand the factors that can contribute to spring wear and tear. Cyclic stress, which involves the repeated loading and unloading of a spring, can weaken the material over time, leading to permanent deformation or failure. Material fatigue is another common cause of spring failure, as micro-cracks can form in the spring due to repeated loading and unloading. Corrosion is also a significant factor, as it can weaken the spring material and make it brittle, leading to cracks and fractures.

To mitigate the risk of spring failure, regular maintenance is essential. This includes cleaning, lubrication, and inspection to identify any potential issues. It is also important to replace worn-out springs promptly to avoid safety hazards and equipment malfunctions.

When selecting a spring, it is crucial to consider the specific design requirements and consult with spring manufacturers. Stock springs are typically intended for prototyping, and their use in production may compromise the overall design. Custom springs, on the other hand, can be designed to meet specific load and travel requirements, ensuring optimal performance and longevity.

In summary, a longer spring can provide benefits such as increased preload adjustability and reduced stress, contributing to a lower likelihood of failure. However, it is important to consider the potential trade-offs, such as increased weight, and consult with experts to ensure the spring selection aligns with the specific application's requirements.

A longer spring will have a lower spring index, which will increase costs

A spring's index is a term used in mechanical engineering to describe the ratio of a coil's mean diameter to the diameter of the wire used. This number is important for determining a spring's suitability in the design phase, as it indicates the ease of manufacturing as a function of cost.

A longer spring will have a larger outer diameter, which will increase the mean diameter of the spring. As the spring index is the mean diameter divided by the wire diameter, an increase in the mean diameter will result in a higher spring index.

However, according to the spring index calculations, a spring index of above 25 is considered very expensive and difficult to manufacture. This is because, as the spring index increases, the production costs also increase. This is due to the need for unique equipment or procedures for production. Therefore, a longer spring with a higher spring index will likely increase costs.

It is important to note that the spring index also affects the spring's characteristics such as flexibility and stress distribution. A higher spring index will result in less curvature in the wire, increasing the spring's resistance to bending stress and contributing to a longer service life. On the other hand, a lower spring index will result in a higher tension curve, which can shorten the spring's functional life.

In summary, a longer spring will have a higher spring index, which can increase costs due to the need for specialised manufacturing processes. However, a higher spring index can also provide benefits such as increased resistance to bending stress and a longer service life.

A spring with a higher preload will be stiffer

A spring with a higher preload will have a shorter spring length, which may make it feel stiffer, but it is actually just harsher. Preload increases the amount of energy required to compress the spring. In other words, it takes a bigger bump to start compressing the spring.

The preload adjustment also raises the ride height, making the bike sit higher or lower on the damping part of the shock. However, preload does not change the spring rate. The spring rate of a linear spring is determined by the distance between the coils, with closer coils being easier to move and spread-out coils requiring more energy to compress.

While preload can compensate to a certain extent for a spring that is too soft or too stiff, the best option is to change the spring itself. A spring with a higher preload will not be stiffer, but it may feel stiffer due to the increased force required to initiate compression.

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