Peloton Shapes

[quixoticgeek]

Ok, todays trying to understand grand tour racing question:

I know that different conditions create different shaped pelotons, such as Echelons coming from cross winds. But I'm wondering, what conditions create the really long single file line like we've got in todays stage?

J

[LittleWheelsandBig]

No crosswind (probably no wind or headwind), lots of power at the front.

[ScumOfTheRoad]

Not really relevant to your question. But interesting. Here is a Computational Fluid Dynamics simulation of a peleton with 121 riders
https://www.sciencedirect.com/science/article/pii/S0167610518303751

[Samuel D]

Yeah. Fast riding at the front combined with a lack of reason for the GC guys to compete for position at the front.

Tailwinds are more likely to create a strung-out peloton than headwinds, since they make the racing harder for the people behind.

(As anyone who’s ridden in a large group knows, drag in the middle is low but a lot higher than 5–10% of a rider on their own. I think that CFD simulation merely shows the limits of CFD modelling, as do the claims of manufacturers of aerodynamic wheels and the like.)

[LittleWheelsandBig]

I didn't find tailwinds strung out the field more than headwinds when I was racing but YMMV. In a block headwind, you'd be scrabbling for the wheel in front as the slightest bit out of position would be like hitting a brick wall. When you're on the rivet just sitting on a wheel, you can't afford any waste of effort.

[Frank9755]

Peloton width could be more to do with tactics and stage of the race than conditions.  eg if several teams are pushing for the front, such as in the run up to a sprint, it can be 10-wide.  If one team is putting a lot of pressure on on their own, such as chasing down a break which is threatening their guy's GC position, likely to be long and narrow as everyone else tucks in behind and lets them work.

[LittleWheelsandBig]

That situation usually doesn't force a peloton into a single line though, unless everybody is on the rivet. It is too easy for a rider to open a gap (deliberately or otherwise) and split the field when it is completely strung out. Usually a peloton chasing hard will widen out into 3-5 wide not too far from the front, so that riders are more likely to be in front of gaps or crashes.

[Exit Stage Left]

The heyday of 'Cipo' saw the peloton drawn out to its greatest extent. His lead-out train would sit on the front at 60km for the run-in to the sprint. That was before the advent of 'traffic-calming'.

I wonder if the GC teams like the idea of a narrow peloton to thread their way through all the street furniture we have now. Relinquishing control to the dominant leader's team has safety benefits. The last 3 kilometres are a bit different, as accidents there won't lose time for the GC contenders.

[Mr Larrington]

Not much wind at all today, thereby depriving *** and Super D of about 35% of their subject matter.

[gonzo]

Not really relevant to your question. But interesting. Here is a Computational Fluid Dynamics simulation of a peleton with 121 riders
https://www.sciencedirect.com/science/article/pii/S0167610518303751

This is amazing!

[LittleWheelsandBig]

Like SamD, I don't believe there is THAT much reduction in drag (though there certainly is a big drop).

[ScumOfTheRoad]

Here is the same CFD study, explained a bit better
https://www.ansys-blog.com/executing-successful-peloton-escape/
Sorry if I am getting boring, but I think this is interesting.

[Exit Stage Left]

The peloton is also a social entity. It is possible to save energy within the main group, but someone is still breaking the wind at the front. Those workers are allowed their moment in the sun in a breakaway.

Within the peloton are actors whose understanding of the dynamics is more sophisticated than the computer models. They work out how long the break deserves in the limelight, and when to put the hammer down to force a sprint finish. Their role is diminished by rider radios, but they could still do the same job with information from the motorcycle boards, with less certainty, so wins from breaks were more common in the past.

My favourite ever stage was when Eros Poli staged a break which saw him win over Mont Ventoux. Another rider had tried to stage a break on a hot day, and Poli rode up to police him. Poli was popular enough for no-one to follow, and big enough for a victory to look unlikely.

The Grand Tour Peloton is a symbiosis between workers, sprinters and climbers. Breaks are a reward for the workers, and sometimes they succeed. The cobbled stage was also a gift for the workers, the fact that they emerge looking like they've been down the pit is symbolic of that.