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Will the break survive? Chapatte’s Law might have the answer

Commentators often talk about the break needing one minute per 10 km. But is it that simple?

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Flat stages at professional men’s bike races often follow a similar script. Initially a breakaway will get up the road and build an advantage of a few minutes or more – depending on how much rope the peloton wants to provide. Then, at some point, the peloton will start to tug on that rope, gradually reeling the breakaway in ahead of a sprint finish.

Most of the time the peloton times the chase perfectly. The breakaway is caught with only a few kilometres remaining and the pace is high enough that subsequent attacks aren’t possible. But sometimes the peloton gives the breakaway too much latitude and/or leaves the chase too late. On those rare occasions, the breakaway wins the day.

So how much rope is too much rope? How can the teams of the sprinters – and indeed those of us watching at home – tell whether a breakaway is going to go the distance? Chapatte’s Law can help.

Chapatte’s Law?

Robert Chapatte was a French cyclist who raced as a professional in the 1940s and ’50s before becoming a commentator on radio and TV.

Chapatte’s theory, based on his experience as both a racer and commentator, was that a chasing peloton would need 10 km to close down a gap of one minute to a lone leader. A gap of more than one minute meant the lone leader would survive. Anything less and the peloton would make the catch in time. That rule could then be extrapolated to two minutes at 20 km, three minutes at 30 km, and so on.

To this day you’ll hear TV commentators reference Chapatte’s Law, if not by name, then certainly by the fact the breakaway will need a one-minute gap with 10 km to race.

It should be obvious that this is anything but a hard-and-fast rule. There are a multitude of variables that can determine whether one minute is enough time for the breakaway with 10 km to go.

Terrain and roads

Chapatte’s Law is best applied on flat sprint days without too much climbing. Ups and downs introduce a whole host of variables into the mix.

How much climbing is there? Are the domestiques of the sprinters able to maintain the necessary tempo to catch the break while tackling each and every climb on course? Are the sprinters able to? It’s no coincidence that most breakaway victories happen on hillier days.

Uphill or downhill finishes take things to another level again. A chasing bunch (often heavily reduced in number by that stage) can make up significantly more time on an uphill finish (some estimates suggest as much as two minutes in 10 km).

The reverse is likely true for a downhill finish. The peloton is unlikely to make up significant time on a smaller group while descending, particularly if that descent is technical.

The nature of the roads can have an impact even on flatter stages. On wide straight finishes, the peloton is at an advantage. If the closing kilometres are on narrow roads with lots of twists and turns, where positioning is tricky in the bunch, the breakaway might need slightly less time.

Hills change the equation.

Nature of the breakaway

Of course, the size and composition of the breakaway plays a role as well.

Chapatte believed that a lone rider with a minute’s lead with 10 km to go was more likely to survive than a larger breakaway. His reasoning was that bigger groups are prone to a lack of cooperation in the closing kilometres; that riders tend to attack one another late (those who don’t back themselves in a sprint, say) and watch one another for such attacks. In doing so they reduce the consistency and strength of the effort they’re putting into maintaining a lead.

A lone rider has no such concerns. They’ve got no choice but to commit to a 100% effort all the way to the line.

Chapatte’s reasoning is solid, but the opposite could also be true. If a breakaway is committed for long enough, that means more riders sharing the load, sharing time in the wind.

Again, it’s not clear-cut.

Nature of the peloton

The nature of the peloton is also a factor. How many teams are committed to chasing down the breakaway? Just the one? Five? And how many riders are those teams committing to the chase?

Is it just the sprinters teams on the front? Or are GC teams contributing too?

A more concerted chase behind is only going to increase the peloton’s chances. If it’s just one team trying to reel in the break, that might be a different story.

Modern cycling

It’s worth reiterating that Chapatte’s Law is well over half a century old. Road cycling has come a very long way in that time. Teams are more professional than ever, sprint trains are more organised than ever, and many teams employ riders specifically to keep breakaways in check, and to chase those breakaways down.

What’s the result of that? Well, some have theorised that, nowadays, it’s more likely a peloton can close down as much as 90 seconds in 10 km, rather than one minute. Anecdotal evidence seems to support that theory – just this week, on stage 4 of the 2021 Tour de France, solo leader Brent Van Moer (Lotto Soudal) had a one-minute lead with just 8 km remaining. The Belgian was caught just before the line. At the extraordinary 2019 Amstel Gold Race, a Mathieu van der Poel-led chase group seemingly closed down one minute over the space of just 3 km.

These are just two examples. To make a compelling revision to Chapatte’s Law, more data would be required.

A useful framework

It should be clear by now that Chapatte’s Law is anything but clear-cut. As in all facets of bike racing, there are so many variables that affect whether this ‘law’ holds true in a given instance, all these years later. It should be noted, too, that this law was initially proposed in the context of men’s racing. Whether it holds true in women’s cycling – where race, team, and peloton dynamics are considerably different – is not clear.

In the context of top men’s races like the Tour de France, though, “one minute per 10 km” has a great ring to it. Decades after Chapatte’s Law was first coined, it remains a relatively useful baseline measurement to quickly gauge how a bike race might play out.

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