How much slower is cross-chaining and how can I avoid it?

You’ve probably heard that cross-chaining is inefficient and bad for your bike. In fact, it’s probably not as bad as you think

Clock11:00, Sunday 27th August 2023

The term ‘cross-chaining’ describes those gears where your chain is stretched between the inside and outside cogs. cross-chaining comes in two flavours. First, there’s when you put the bike in the small, inner chainring at the front, and the small, outer cog at the back. Secondly, there’s when you ride in the big, outer chainring at the front and the big, inner cog at the back.

If you find yourself in these gears on a group ride, it’s only a matter of time before your riding buddies call you out on it, because riding in either of these combinations leads to increased friction, reduced efficiency, and increased wear on your components.Or so we’ve always been told.

Cycling wisdom has told us that cross-chaining is a massive waste of energy. In reality though, cross-chaining is nowhere near as inefficient as you might think. Research shows that cross-chaining has a small impact on drivetrain efficiency, although it will accelerate drivetrain wear.

Drivetrain efficiency

In any drivetrain, there’ll always be a certain amount of energy lost to friction, but the straighter a drivetrain can be, the lower this energy loss will be. With a conventional chain-driven drivetrain, the most efficient it can possibly be is about 97%. Singlespeed and fixed gear bikes are the most efficient bikes out there, because their chains are always completely straight.

On geared bikes, the chain moves from side to side as it transfers through the sprockets on the cassette and the chainrings on the chainset. As it moves through the gears, the angle at which the chain is held increases and decreases, and the efficiency in the system changes. This is because the plates on the chain will rub on the teeth as they engage and disengage, creating extra friction.

In 2019, VeloNews and Ceramic Speed did some lab tests on this. They tested the efficiency loss of a drivetrain when cross-chaining in either direction, both ‘big/big’ and ‘small/small’, when riding at 250W. They used a standard 53/39 tooth chainset and an 11/34 tooth cassette.

First of all, they measured the efficiency when the bike was cross-chaining across the smallest chainring and the smallest sprocket. In this gear, there was an efficiency loss of 15W from that 250W that was being put through the pedals.

By comparison, when riding in the equivalent gear, which is the 53 tooth chainring at the front and the 15 tooth sprocket at the back, there was an efficiency loss of 10W, despite the fact that the chain is almost perfectly straight in that gear.

So the efficiency loss from cross-chaining in the smallest cog at the front and the smallest cog at the back is only 5W. That’s about the same as the difference between aero socks vs normal cycling socks, or the difference between having a clean or a dirty chain. Not much at all.

Then, they measured the efficiency of cross-chaining in the other direction, in the biggest chainring at the front and the biggest sprocket at the back. Remarkably, in this gear, the efficiency loss was just 10W, which is only 1W more than in the equivalent, straighter gear of 39/25. How can this be? It’s possible that the efficiency gains from riding in the larger cogs cancelled out the efficiency losses from cross-chaining.

For our discussion of cross-chaining, these results are really interesting: contrary to popular belief, cross-chaining doesn’t slow you down by much at all. The small/small combination costs about 5W over the equivalent gear, and the big/big combination costs only 1W in efficiency.

This explains why we’ll often see the pros cross-chaining in the big chainring. To avoid the hassle of changing up and down in the front gear, many pros stay in the big chainring for as long as possible. It doesn’t cost them much in drivetrain efficiency, and it means they can keep the power down without having to lay off momentarily as they shift between the big and the small chainrings.

What about drivetrain wear?

For many of us, efficiency is far less important than durability and longevity. cross-chaining might be more efficient than we’d have thought, but if it’s going to ruin our chains and cassettes, it’s not a good idea for most riders. So is it bad for our bikes?

In 2022, Road.cc reached out to Shimano, SRAM, Campagnolo and FSA and asked them about the impact of cross-chaining on component life. Granted, these brands might not be the most unbiased people to ask about the performance of their products, but their responses are interesting nonetheless.

Shimano and Campagnolo both said that cross-chaining can add wear and tear to chainrings and cassettes. When cross-chaining, the plates of the chain rub on the teeth, wearing away at the chain and the teeth themselves. Over time, that leads to the degradation of the components and poor shifting performance.

Interestingly, SRAM and FSA were more positive about cross-chaining. FSA said that cross-chaining is increasingly common. Instead of telling customers how to use their products, FSA decided to “invest in the development of much stronger chains”. SRAM went further, encouraging riders to stay in the big ring whenever possible: “we love big-big”. On the durability front, SRAM said “cross-chaining is not a concern for premature component wear unless of course your chain is wearing through your front derailleur.”

With all the component brands singing a different tune, it can be tricky to know what to do. Our recommendation is to avoid cross-chaining if you want to get the maximum amount of miles out of your drivetrain components.

How to avoid cross-chaining

Here’s Alex Paton and Manon Lloyd’s simple rule to avoid cross-chaining: if you’re in the big ring, avoid the three biggest sprockets on the cassette, and if you’re in the small ring, avoid the three smallest sprockets in the cassette. You can do that by changing gear with the front chainring when you start to approach those limits on the cassette.

Long term, you can reduce the chance of cross-chaining by optimising your gear ratios for the kind of speeds you ride at. If your rides are super fast, on smooth flat roads, a bigger chainset will mean you can ride comfortably in the big chainring and the middle of the set.

If you prefer long, steady rides, maybe on gravel or mixed surfaces, a compact or even a super compact chaining can keep you in the big gear and the middle of the cassette for longer.

Other considerations

If your chain is rubbing on your derailleur it’ll give you a far greater efficiency loss.

Changing between the big and small chainring isn’t just about drivetrain efficiency. There are a couple of practical considerations too.

Firstly, there are a few situations where the time loss from changing into and out of the small chainring outweighs the efficiency gain from having a straighter chainline. And if chain wear is your main concern, it’s worth remembering that shifting between the front chainrings puts a lot of stress through the chain. In our experience, a chain snap out on the roads almost always comes during a gear change on the front chainrings.

Secondly, riding in the big chainring can help with chain retention. On cobbles, gravel or just rough roads, changing into the big ring, or cross-chaining to remain in the big ring, can help keep the chain on the teeth. In the big ring, the chain tension is higher, as the derailleur is stretched further on its spring. That means that the chain is held more securely on the teeth, reducing the chance of a dropped chain.

Finally, it’s worth saying that to increase efficiency and the life of your chain, the most important thing is to make sure that your gears are indexed correctly, kept clean, and properly lubricated. If your chain is rubbing on the front derailleur due to incorrect indexing, or if your chain is dirty or lacking chain lube, the wear on your components will be accelerated, and the efficiency of your drivetrain will be reduced. Ultimately, indexing and maintenance will have a far greater impact on your drivetrains health and efficiency than whether you cross-chain or not.

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