Why should you avoid crossing the chain?

In cycling groups, training groups, or from the most experienced riders, you often hear that you should avoid crossing the chain. Why shouldn’t you ride in the small chainring with a small sprocket—or, conversely, the large chainring with a large sprocket? Here are some answers.

By Pierre-Maxime BRANCHE – Photos: @3bikes.fr

First and foremost, know that it’s absolutely not forbidden to cross your chain, whether on the small or large chainring. It won’t stop you from moving forward, and you won’t be taking any particular risks. However, it will affect the wear and performance of your drivetrain—as well as your wallet. Here’s why.

Premature Wear

When you cross your chain, you’re forcing the sprockets to work sideways rather than in a straight line. However, a chain isn’t designed to operate laterally. While the latest chains are flexible enough that you won’t lose too much efficiency due to friction when riding with the large chainring and large sprocket, this isn’t ideal in terms of wear and tear. When the links are positioned sideways, they engage the cassette sprockets and chainrings from the side. They sharpen them—that is, the tip of the sprocket becomes pointed—which weakens it and causes premature wear that wouldn’t occur as soon if the angle of contact had remained straight and in line. This sprocket wear has other consequences: it increases the risk of the chain skipping. Crossing your chain over the small sprocket or the large sprocket has the same consequences. The only difference is that there is a greater risk of the chain skipping on a small sprocket than on a large one; furthermore, the wear consequently affects the chain and the chainrings. There is even a risk of chain breakage, since premature wear is abnormal wear.

There is a higher risk of the chain jumping off a small sprocket than off a large one.

This is even less advisable with a triple chainring setup (which has become very rare) because when you position the chain on the smallest chainring on the left and the smallest sprocket on the right, it will be in an even more crossed position. Riding with a crossed chain should therefore be limited to occasional use, especially since there’s little benefit to it given the equivalent gear ratios provided by the various chainrings and cassette sprockets—which are specifically designed to prevent the chain from crossing and to ensure more consistent gear spacing.

More Stress on the Chain in the Mountains

Once the chain is worn out—even prematurely—it needs to be replaced. A chain is worn out when, laid flat on the ground, it forms an arc. You can then see how much it has stretched sideways. Another tip: when the chain is on the largest chainring, simply pull lightly on a link near the chainring. If it comes off by more than about 5 mm, it’s time to replace it. This is the simplest way to check. Generally, a chain can last for about 5,000 km with proper use on the road. This is an average under normal conditions—that is, on mostly flat routes and in fairly dry weather. Naturally, extreme conditions—such as mud, for example—wear down the equipment much faster. The same goes for mountain riding: on mountain passes, the pressure on the chain is much greater, so it will wear out faster than on flat terrain.

How do you maintain your chain?

The key is to maintain your chain regularly with a light (but consistent!) application of lubricant, as you don’t want it to get too greasy either. If it does, it will become “sticky,” meaning that dust will tend to cling to it, forming a kind of grinding paste that’s abrasive and will very quickly damage the entire drivetrain. When conditions are good and dry, there’s no need to do this systematically. If you ride in wet weather—like in winter, for example—it’s best to get into good habits. Otherwise, you run the risk of damaging your equipment very quickly and having to dig into your wallet. And if you’re also riding with mismatched tires, the bill can quickly get steep.

-> SEE ALSO: All our Coaching articles