Giro d'Italia TT Analysis

This year's Giro d'Italia is set to come down to a nail-biting time trial finish between Tom Dumoulin and Nairo Quintana. Using Best Bike Split's Time Analysis Tool, we have some predictions for how this exciting race will end.

Giro d'Italia

The 2017 Giro d'Italia will finish into Milan with a Time Trial pitting one of best time-trialists in the world in Tom Dumoulin against the master climber and current Maglia Rosa-wearer Nairo Quintana. The Giro, with its unrelenting mountains, is traditionally won by a climbing GC specialist, but over the past few seasons Dumoulin has risen to the climbing challenge while still retaining his expert ability against the clock.

This year's edition suited Dumoulin more than in previous years with the inclusion of two pure time trial courses. In the first (stage 10), he proved his dominance and pulled on the Maglia Rosa by putting two minutes and 53 seconds into Quintana, but that course was almost 40 km and came after a rest day.

The final Stage is 10 km shorter at only 29.37 km — and comes after a brutal string of mountain stages. With Quintana back in the lead, let's examine the final stage and see what type of time gap Quintana will likely need to hold off a motivated Dumoulin.

Stage 21: Monza to Milano

The final stage in the Giro d'Italia is a 29.37 km race against the clock starting at the Autodromo Nazionale race track in Monza before traveling southwest into the heart of Milan. The course has a slightly negative gradient and long stretches of straight roads where a specialist can open up the throttle. The real question for Dumoulin will be if there are enough kilometers to make up the time he will need on Quintana.

Giro d'Italia Course

Because we won't know how much time Dumoulin will need until tomorrow's final stage in the mountains, we will instead analyze how much time Quintana will need going into the stage to retain the jersey.

To do that we have done some modeling using Best Bike Split's Time Analysis feature to give some estimates for the two riders from the Stage 10 TT. Based on the results and some estimated CdA (aero data), we came up with the following estimated power values for the stage:

Rider Time Est. Power Est. Watts/Kg
Tom Dumoulin 50:37 425 watts 6.06
Nairo Quintana 53:30 350 watts 5.88

Stage 10 Power Estimates based on Finish Time

What is interesting to note here is that while Quintana's estimated Watts/Kg is a bit lower than Dumoulin, even if he were to bring it up to 6.1 on this course he would gain 50 seconds if it were due to increased power or only 17 seconds if it were due to decreased weight. In a true time trial without much climbing and with similar aerodynamics between riders, it all comes down to FTP (Functional Threshold Power).

To run some "what if analysis" check out the Time Analysis Tool and try adjusting the drag, power and weight sliders.

Using the numbers above we can model out Stage 21 to see the differences between the two riders. Though the course is 10 km shorter, which at world class speeds would typically result in approximately a 1% to 2% power increase on fresh legs, we can expect riders will be hard pressed to get much of an increase due to the fatigue of multiple mountain stages. The following two images show the time difference that could be seen between the two riders:

Quintana Estimates

Estimated Finish Time for Nairo Quintana

Dumoulin's Adjustments

Adjustments for Dumoulin's Estimated Drag, Power, and Weight

This course is perfectly setup for Dumoulin. Despite being shorter than Stage 10 by about 10 km, he should be able to take full advantage of his power disparity and put more than two minutes into Quintana. Because the course is primarily flat with a slight negative overall grade his additional weight has little to no impact and will actually help in some sections.

One major factor on the race that we haven't discussed are wind conditions. While both riders will experience the same conditions, a prevailing strong tailwind will actually help Quintana as it should speed up both riders and narrow the time gap. The current forecast is for low slight head wind to crosswind.

Forecasted Weather

If the wind shifts to more of a direct head wind and increases in strength, Dumoulin could put even more time into Quintana. A quick wind analysis below shows the impact of a stronger 15 km/h head/tail wind along with the current forecasted weather:

Wind Conditions Est. Dumoulin Time Est. Quintana Time Difference
As Forecasted 34:48 37:03 2:15
Head Wind (15 km/h) 36:13 38:41 2:28
Tail Wind (15 km/h) 33:00 35:01 2:01

I believe Quintana needs to gain at least another two minutes in the penultimate stage tomorrow to feel safe, and even then a hard charging, determined Dumoulin might take back the Maglia Rosa on the final day!

View the BBS model for Stage 21 and try some adjustments in the Time Analysis tab to see how changing drag, power, and weight factors could change the race. We will update the forecasted weather right up to race time.