If you watch the one-day Classics, you’ll notice that the gap between the breakaway and the peloton rarely follows a smooth pattern. The tempo in the peloton varies and the gap concertinas: at times it tumbles rapidly, while at others it may even increase. One minute the break appears doomed, then five minutes later they suddenly have the upper hand. Why does this variation occur, why is it important, and how does it add to the excitement?

Ebb and flow

This slow-quick-slow-quick tempo seems counter-intuitive at first. After all, the most efficient way to cover a long distance is at an even pace. A car enjoys its lowest fuel consumption at a steady speed. And if you’re running in a race, you will finish most quickly if you settle into a comfortable rhythm rather than, say, alternating sprinting and walking.

Indeed, that is exactly what a well-functioning breakaway does. Each rider shares the load by taking equal pulls on the front (where the most energy is expended) and the group seeks to maintain a stable, efficient power output.

In theory, the peloton should work the same way. By riding steadily 1.5-2kph faster than the smaller group – no problem for a large bunch – even a ten-minute gap can be easily closed before the finish.

In practice, what we often see is rather different as the chess game plays out. The gap can drop rapidly on the flat as teams contribute additional riders to the front of the peloton. Equally it can grow again if teams withdraw support from the chase.

When the going gets tough, the tough speed up

However, it is on the hills and cobbles – and in particular the double-whammy of cobbled hills – which are dotted throughout the Classics where we are most likely to see dramatic changes of pace. It is here where the greatest dangers lie: a split in the bunch on a tricky climb (as occurred on the Taaienberg at Omloop Het Niuewsblad), a touch of wheels or handlebars resulting in a mass crash, or individual misfortune such as a puncture or an unshipped chain.

If you were riding on your own, common sense dictates you should slow down. In a racing situation, however, the opposite is true. It’s a pattern you will see time and again on the approach to a punchy climb or a section of pavé: the peloton speeds up as all the key riders (and their teams) try to muscle their way towards the front to minimise the risk of being caught behind an incident.

In particular, watch what happens on the approaches to the trickiest sections of cobbles in Paris-Roubaix. The teams of top contenders such as OPQS’ Tom Boonen or RadioShack’s Fabian Cancellara will send a train to the front and effectively execute a full-on lead-out to both keep their men out of trouble and potentially split the pack.

The net result of these intense bursts is that the breakaway will generally see its advantage drop significantly. They can easily lose a minute or more in the space of 4-5km, as they themselves will have ridden through at a steady tempo without the need to compete for road position.

Varying tempo drives race-defining tactics

What then happens depends on what has happened through/over the obstacle. If the entire bunch is intact, the pace typically drops as everyone pauses for breath ready for the next hill or cobbles. As a result, the breakaway often recovers some of its lost advantage. If, however, the pack has fractured, teams with multiple riders in the newly formed chase group may choose to attack in an attempt to create a potential race-winning selection of their own.

A typical Classics race situation. What do you do if you’re the chase group: press on or sit up?

This is a difficult decision to make, though, with several variables to consider. Firstly, there is the high level of risk involved in expending energy so soon. Get it wrong, and you may not have the legs to respond later. Then they must rapidly weigh up the composition and the numbers in their group versus both the peloton and the initial breakaway, and the gaps between the respective groups. Go for it with an insufficient number of riders trying to bridge too large a gap, and you will never catch the break or will be easily swallowed up by the peloton. Hesitate, and the narrow window to make your move rapidly closes as the peloton reasserts itself.

These fluctuation of pace – and therefore attacking opportunities – occur multiple times on a Classics parcours, which makes the racing unpredictable and tactically complex. This slow-quick-slow tempo is not the most efficient way to chase down a break and win a race, but it is far more effective in terms of sorting out the contenders from the also-rans, creating an intriguing ebb and flow where one minute it may look as if the peloton has the advantage, then the breakaway appears to hold the upper hand and then all of a sudden one or two riders jump out and ride away to victory.

There is no better example of this than Tom Boonen at Paris-Roubaix last year, where he executed an audacious long-range break from a four-man group after the peloton had already been shattered. Only briefly aided by OPQS teammate Niki Terpstra, the move initially looked foolhardy but turned out to be perfectly judged. The attack occurs shortly after the start of the YouTube video below.

On such fine lines and brave decisions are races won and lost, and legends and heroes created. Boonen gambled that day and it paid off handsomely, and it was the constant changes of tempo which preceded it that created the opportunity which he seized in such glorious fashion. You’ve got to love racing like that.