The Tour Down Under kicked off today with a prologue that heralds the start of the 2023 World Tour.

However, the Adelaide-based 5.5km sprint race was far from a typical prologue, as it was filled with highly modified road bikes to take advantage of the race's unique ban on time trial bikes.

Due to the logistical difficulties of bringing time trial bikes to Australia along with the teams' road bikes, the race organizers, UCI, and teams agreed to contest this stage on standard road bikes.

Time trial bikes and aero bars were banned, but disc wheels, trispokes, and aero helmets were permitted. As a result, a master class on aero optimization was held with riders and team mechanics.

Many bikes were fitted with time trial wheelsets and shifters, time trial helmets became almost ubiquitous, skinsuits were used by all but a few riders, and aero overshoes were a common sight.

The eventual winner, Alberto Bettiol, with a time of 6:19, filled many aero boxes.

Bettiol did little in his pursuit of aero performance. He removed the bottle from his bike, installed a Vision disc time trial wheel and what appeared to be an 80mm deep front time trial wheel.

He also wore a Rapha time trial speedo, aero overshoes, and aero mitts. On top he wears a POC "Cerebel" time trial helmet, with Vision Metron aero handlebars and Shimano Dura-Ace shifters on the front.

Luke Plapp also took a turn-in-the-hood approach, along with various other aero optimizations. Interestingly, however, newly crowned Australian road champion Luke Plapp has double-wrapped the top of his bars because of the need for padding when running in the "puppy paw" position.

Like the rest of the Ineos Grenadiers team, Plapp's bike was a Princeton Carbon Works time trial wheelset (worth $5700). This wheelset can be seen here mounted on the bike of young Briton Leo Hayter, although it is slightly blurred because it is moving.

Early favorite Rohan Dennis added one more aero optimization. Riding a Cervelo S5 aero bike with a time trial disc in the rear, 80mm deep wheels in the front, TT helmet, skinsuit, overshoes, and mitts, he switched from a conventional double chainset to a single chainring. The removal of the front derailleur and inner chainring was beneficial in terms of both weight and aerodynamics, pushing the two-time TT World Champion to 15th place.

Of all the riders, however, I think Pero Bilbao won with the most aggressively aero optimized setup.

We have already mentioned the turn-in shifter on the Bettiol and Plapp, but Bilbao on the Bahrain Merida took it to the extreme and made it almost horizontal. Moreover, if you look closely, you will see that the top is taped, but the drop of his bar is not.

Bilbao also took the same approach as Rohan Dennis, removing the front derailleur and sticking with a single chainring. Unlike Dennis, he opted for no chain keeper and relied on the clutch of his Dura-Ace rear derailleur to keep the chain in place. Although he was closer to an aero win, the risk of a chain drop on the city course was greater.

All of this in addition to TT wheels, helmets, speedos, mitts, and overshoes, which are ubiquitous.

Bilbao was also one of the only riders to run the course with a team car. There has been much debate about the aerodynamic benefits to riders of following team cars. For this reason, the UCI introduced a rule in 2023 limiting the distance a team car can follow.

Bilbao was also hampered by the weather, finishing in 25th place, 20 seconds behind Bettiol.