Renold - Troubleshooting Guide: Fatigue

Your classic motorbike is likely your pride and joy. Something you look forward to riding at a weekend. But as a working machine exposed to the elements, you need to take care of it. This means keeping it clean, lubricated, and in good working order. Doing so will prolong the life of your motorbike and ensure it's always ready to ride.

General Tips for Looking After Your Motorbike:

As mentioned in other articles, regular care of your motorbike is always better than fixing issues when they become apparent. This is no different from fatigue.

Here are a few key points on how to keep your bike in the best condition possible:

1. Keep your chain clean and lubricated - This will help reduce friction and wear, making your chain last longer.
2. Inflate your tires regularly - This will help traction and handling.  
3. Inspect your brakes regularly - This is critical for safety!
4. Keep your bike clean - This will help it look nicer but, more importantly, ensures it lasts longer by removing corrosive elements that naturally build up.

Following these tips should help you take care of your motorcycle and keep it running smoothly.

What is Chain Fatigue?

Fatigue typically occurs due to an excessive load being placed on the chain. However, there are three failure modes worth mentioning;

Overload

The chain is subjected to a large, excessive, one-off load. This unreasonable load is so extreme that it causes permanent deformation of various chain elements. This leads to a very short chain life once it occurs.

Fatigue

A chain is subjected to repetitive high load beyond the endurance limit. The load is not as extreme as in cases of Overload, but over time, it weakens the chain until it eventually fractures.

Wear

Typically, this happens over a longer timeframe. While Overload and Fatigue can be avoided by not subjecting a chain to excessive loads, wear is unavoidable as it's the natural process of material in the chain wearing away. As this occurs, the chain stretches beyond its usable limit.

Understanding Overload

Signs of Overload include;

• Deformed material
• Potentially visible stretching of the chain's side plates
• In extreme cases, the chain pins might break

Understanding Fatigue

This is essentially the same as Overload, but when the load is not as extreme. The application of these 'lesser' loads is not usually enough to stretch a chain to the extent of Overload, but damage builds up over time.

Fatigue is more challenging to spot than Overload but no less severe. 

As with Overload, once you spot these signs, it's too late to fix the issue. Instead, the chain must be replaced before a serious accident can happen.

Understanding Wear

As stated above, while Overload and Fatigue can be avoided, wear cannot. Wear is simply the natural process of your motorbike's chain mechanics rubbing against each other. While it cannot be prevented entirely; the following factors can exacerbate wear;

• Higher loads being placed on the chain
• Environmental factors that dry out lubricant or cause debris to enter the chain mechanic, thus increasing the amount of rubbing occurring

What Causes Increased Load On a Chain? 

As can be seen, excessive chain loads are the most significant cause of chain fatigue that we can both control and prevent. So, what adds load to a chain?

The simple answer is anything that forces the chain to work harder. Of course, the load is applied as soon as a motorbike starts moving, but all chains are designed to work under certain load limits without issue.

Problems occur when these limits are exceeded. Below are the common factors that increase the load on a chain;

• Weight – The more a chain must 'pull,' the more significant the load it has.
• Operating in the wrong gear – This can exacerbate the above two issues. Forcing the chain to work in the wrong gear increases the load.
• Friction – A chain that is not well lubricated or has debris stuck in the mechanisms can significantly increase the load on a chain as it's forced to work harder.

Preventing Fatigue

While fatigue can cause serious issues, avoiding it is relatively simple. You just need to do two things, which you likely already do;

• Undertake regular cleaning of your chain, especially after long rides through environments that invite debris into the chain mechanism
• Keep the chain well lubricated to reduce friction and allow for smooth movement between elements.