spinconn

Despite loving all things related to cycling I have never really understood the professional racing world. I never raced and never watched racing other than the major network coverage of the Tour de France each year. This year I took advantage of the increased opportunities to watch cycling races afforded by the internet and watched the entire Giro d'Italia. Boy, did I enjoy it, and especially the process of learning a little about it from the expert commentators.

I think I have some idea of what kind of traits it takes to be a good mountain climber, a good sprinter, and a good GC captain or domestique but one thing I have not figured out at all is the time trial. I am not even sure I understand the reason a time trial exists in a grand tour. I have ordered a book about pro cycle racing, which has not yet come, but my google research has not left me very much educated on time trials. What kind of talents make up a good time trial rider?

datlas 

High FTP = big aerobic engine

Broctoon

To be good at time trials, a rider must sustain high continuous power output, and must be able perform in a really aero tucked position, since drag reduction is everything. It's a whole different sport from regular road racing, where teams work together and can strategize in many ways to take advantages of each member's strengths, as well as drafting off other teams' riders.

No climbers vs. sprinters vs. all-rounders. Just who can get really aero and then put out big watts continuously.

They're included in grand tours to give the riders and teams exposure to a whole spectrum of racing challenges. In other words, for the same reasons the tours include big climbing stages, long distance stages, etc.

alcjphil

To win the overall in a grand tour one must be a complete rider in all situations. The time trial is known as "the race of truth", meaning that the rider must be able to put out maximum power for an extended period of time and as well maintain an aerodynamic position on the bike to take maximum advantage of that power output. In an individual time trial, your teammates cannot help you, your result is up to you and you alone. A variation of this is the team time trial where the whole team works together to cover the distance.

surak

Time trials near the end of a grand tour have led to some of the most dramatic GC outcomes - Lemond v. Fignon, Pogacar v. Roglic, Roglic v. Thomas.

While the typical ITT is a bit boring for race watching, TT bikes are less constrained by the UCI than road bikes so there's more tech to geek out about as teams and riders optimize everything they can.

Bah Humbug

In the past decade and change the riders have started to actually pay attention to the TTs, and it shows. When I started watching many would put their heads down and the tail of their TT helmets up into the wind, over and over, a dozen or more times per minute. It used to be very clearly not a thing most cared to improve, at all.

merlinextraligh

Sustained climbs are all about w/kg. A relatively flat TT is all about watts to surface area. Given the relationship of surface to volume as people get bigger ends up with surface area increasing less than volume, ie weight, , larger riders can have a much better power to surface volume ratio than power to weight ratio. See, e.g. Fabio Cancellera.

So TTs are somewhat the equalizer for bigger riders, against the tiny climbers.

On a much smaller stage, it explains why I can be pretty competitive time trialing and racing crits, and get destroyed in a hilly road race.

alcjphil

You forgot Hesjedal vs Rodriguez 2012 Giro

PeteHski

TTs in Grand Tours basically separate GC riders from specialist pure climbers. GC riders have to be very strong climbers and very strong TT riders. Without the TTs Grand Tours would be won by the lightest specialist climbers, who are not true all-rounders.

RChung

Not watts to surface area, watts to drag area.
A composite measurement is watts^2/(kg*CdA). That turns out to be a pretty good predictor of TT performance.

merlinextraligh

ok I stand corrected, however, the biggest determinant of cda is going to be surface area, and with an equally good position on the bike larger riders tend to have an advantage because their power tends to be higher as a percentage of their surface volume compared to smaller riders.

So while your answer is clearly more technically correct, I think my less technical explanation is still basically correct.

RChung

Depends. If you look at the figures on the right side of the page at https://en.wikipedia.org/wiki/Drag_coefficient you'll see that Cd can vary pretty widely with shape (i.e., for the same frontal surface area), like 2 orders of magnitude.

Deep wheels don't affect A, but they affect Cd so CdA decreases.

Wrinkles on the back of your jersey don't affect A, but they affect Cd so CdA decreases.

The angle of your forearms in the wind don't affect A, but they can affect Cd, so CdA can sometimes decrease.

Aero helmet or socks or or wide forks or aero shaped frame tubes can *increase* A, and lower Cd so CdA decreases.