Castelli launches new Free Aero Race 4 Bib short

Team Sky’s new shorts hit the shops today

Italian sportswear brand Castelli has today released the latest version of its pro-level bib short, the Aero Race 4, to the general public.

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The Aero Race 4 is an update to the lightweight, minimalist, aero shorts worn to Tour de France and Giro d’Italia victory by Team Sky’s Geraint Thomas and Chris Froome.

BikeRadar’s very own Content Director, Rob Spedding, had the arduous task of testing the new shorts
Castelli

I’ll be honest, the updates feel pretty subtle, but that’s not surprising considering every iteration of the Free Aero shorts since the first in 2007 has performed well in our tests and, probably more importantly, under the backsides of pro race winners.

Wearers of the previous model will notice a new strap construction — the stripe mesh used is super-thin and featherweight to aid breathability. These are the sort of straps that ruche up when you pull them out of the drawer, but they do lie completely flat and comfortable once on.

Elsewhere, Castelli is, unsurprisingly, continuing with its dual-layer Progetto X2 pad although this has been updated and is now the Progetto X2 Air Seamless. The top layer is a seamless, anti-bacterial fabric that isn’t attached to the pad below, which is thicker where you need it under the sit bones. This means that the pad rather than your skin can move around, reducing friction on delicate areas.

Rob leads out the test ride
Castelli

The shorts themselves are, as you’d expect at this level, of multi-panel construction with flat-lock seams for comfort. The outer panels use dimpled Vortex fabric, which Castelli says offers aerodynamic benefits, while the Giro4 leg grippers use thin vertical strips of silicone to keep the laser cut legs in place.

I wore the new Free Aero Race 4 shorts on two rides at their launch and my initial verdict is that Castelli’s evolution of this model has been successful. They’re comfortable and supportive without feeling restrictive.

It wasn’t warm enough to give an opinion on breathability, but the Progetto X2 seamless pad is excellent.

Castelli Aero Race 4 Bibshort details

Castelli Aero Race 4 Bib short front
Castelli
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  • Weight: 172g (size large, claimed)
  • Sizes: S–3XL
  • Wearable temperatures: 15–35 degrees
  • Construction: Progetto X2 Air seamless seat pad, Giro leg gripper elastic, Forza fabric on inner legs, Vortex damped fabric for aero performance
  • £150 / $199.99  / AU$265.00
Castelli Aero Race 4 Bib short back
Castelli