Given that Castelli are the cycling and tri suit atelier of choice for one of the fastest women in triathlon right now (Laura Philipp) you’ve got to assume this is a brand who know a thing or two about aerodynamics. And their new Aero Pro 8S cycling kit range (they say the S stands for “speed”) comes as the result of a decade’s worth of research and innovation on reducing drag and dropping watts. Claiming up to a 6% CdA saving over previous aero jerseys, the Castelli Aero Pro 8S has the potential to bring speedsuit performance to your everyday cycling kit.

But will that come at the cost of comfort? I’ve been testing out the Aero Pro 8S women’s cycling jersey during my long training rides as I get stuck into my key Kona training block to find out!

Key features

Race fit	Lightweight fabric ideal for hot conditions
Bonded sleeve endings	Engineered aero shoulder fabric – up to 6% CdA saving
3 rear cargo-style pockets	Elasticated waist with silicone gripper at the back
YKK® Vislon® zipper – easy to adjust on the move	Colours: Black, Belgian Blue, Silver Grey, Multicolor Purple
Sizes: XS-XL	RRP: £175 GBP / ~$230 USD / ~€200 EUR

Summary: The TL;DR overview

Ultra-aero and super comfortable often don’t go hand in hand. But this is a cycling jersey where almost every detail has been considered. Aero features like the ribbed shoulder material and a second skin fit gives it that race day feel – whenever I wear this jersey it’s like it flips a switch mentally that has me wanting to go hard even when I’m supposed to be riding easy! But finer details, like soft-touch lightweight fabric, bonded seams and a waist elastic that stays put mean that need for speed doesn’t leave you wanting on the comfort front. And where other race jerseys forego practicality, the three rear pockets give you plenty of storage to keep all the essentials handy.

The verdict: it’s giving ‘pretend I’m in the Tour de France Femmes’ performance, with Ned Flanders ‘it’s like I’m wearing nothing at all’ comfort, and I’m here for it.

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First impressions

Fresh out of the box, the first thing that struck me about this cycling jersey is just how soft and lightweight the material is. The sleeves are a slightly more rigid fabric with aero ribbed detailing over around the shoulders – which Castelli say can take up to 6% off your CdA compared to previous jerseys. And then ventilated panels under the arms. The main body of the jersey is an ultra-lightweight almost mesh-like fabric, which is super breathable, really nice and soft – and has the perfect amount of stretch to give a second skin fit without being uncomfortable.

There’s not a scratchy seam in sight, and you’ve got a zip guard at the neck to make sure it’s not going to irritate you, even when you’re riding down on the drops or in the aero bars. The elasticated waist band is subtle but wide enough that it doesn’t dig in, create unflattering lines or pull at the fabric of the jersey. And you’ve also got a gripper on the inside at the back to keep the jersey in place while you ride.

I’ve been testing this jersey out in two of the colour options – the ‘Belgian Blue’ which is a nice deep navy. And the ‘Multicolor Purple’ which with its mix of light and dark purple tones and a marble effect is seriously stunning!

Sizing

I’m generally a UK size 6 (US 2) on top, with not much going on underneath the old sports bra. In other brands, I usually take a size XS cycling jersey. But by Castelli’s size chart I needed to go for a S in this jersey. That fits perfectly, but where a S jersey in other brands might correspond to a UK 8-10, I’d say here it’s definitely more of a 6-8. So don’t be surprised if you need to size up – especially if you’ve been a blessed with more of a chest than I’ve got! Keep in mind it’s an aero/race fit jersey so if you don’t like your kit to fit skin tight you might want to go up two sizes.

The size curve could also do with being a little more inclusive (a running theme for most women’s sports apparel, though there are some brands who are doing this well!). It only goes up to an XL, and the measurements correspond to around a UK size 14 (US 10).

Real world performance

So the at-home try on was a success. But how has this jersey been performing out in the wild? Pretty much all my outdoor rides at the moment are on my TT bike as I’m on the countdown to Kona. And even after multiple hours scrunched up in my TT position, this jersey has been remarkably comfortable. The high stretch fabric means there’s no feeling of ‘pulling’ around the shoulders, and even without much in my pockets (my TT bike has built-in storage for nutrition) the waist band has stayed in place.

For me the sign of a good cycling jersey is the one you forget you’re wearing. If you’re noticing your jersey, it’s probably for the wrong reasons. I’m pleased to report that the Castelli Aero Pro 8S jersey gets the ‘Ned Flanders’ seal of approval. (If you don’t instantly know The Simpsons episode I’m referring to, we probably can’t be friends…)

Fast feeling

Sadly my budget doesn’t stretch to regular wind tunnel sessions (or any wind tunnel sessions for that matter!). So I can’t give you any exact data on whether this jersey knocks anything off my CdA compared to others in my kit drawer. But what I will say, is that I live on the east coast of England where even when it’s “not windy” – it’s always freaking windy (most of my rides do involve me yelling profanities at the head wind at least once). Against those Suffolk coastal winds, this jersey has ‘felt’ fast and there’s certainly been no issues with flapping or bunching.

The race fit and cool design also flips my head into race mode a little bit – I think when your kit feels fast, you naturally want to ride a little faster! So even if it’s purely psychosomatic, the aero fit of this jersey gets a big tick in my books.

Castelli versus the oppressive UK summer heat

Heat? In the UK? Yes my friends, because while these British Isles are known for being cold and rainy. When we do get a summer heat wave like we did recently, it’s the ‘wrong’ kind of heat. The sort of clammy humidity that makes every single room in your house feel like a packed out 6pm underground commuter train carriage, and makes the air outdoors feel like it’s made from gloopy 2-day old soup. I guess at least it’s been good for Kona prep. And despite these steamy conditions we’ve been having recently, this jersey has performed really well on the breathability front. Perfect for summer long rides or high intensity efforts.

So what’s not to like?

Honestly, I’m scratching my head a little here to come up with anything I don’t like about the Castelli Aero Pro 8S women’s cycling jersey. I guess you could maybe say that the lightweight fabric is a little see-through, though that doesn’t bother me and it’s nothing a white sports bra won’t fix. The size curve needs to go beyond an XL to be inclusive. And for some riders, the second skin aero fit won’t be for everyone. Though if you do prefer a more casual fit jersey, it’s unlikely you’d be looking at an aero/race jersey anyway. Other brands, like Stolen Goat with their ‘every day’ range, specifically cater for your easy Sunday riding apparel.

But for me, on the three majors (design, comfort and performance) this jersey passes with flying colours. All the usual minor annoyances you can get in a jersey like a scratchy zip, a neckline that’s too high or too tight, restrictive sleeves that give you Michelin Man arms or a waistband that rides up – so far in my experience anyway, haven’t materialised.

Chapeau Castelli, this is possibly my new favourite cycling jersey!