Castelli Aero Race 5.0 jersey

The Aero Race 5.0 jersey from Castelli is all about performance, and specifically keeping your air resistance to a minimum. It's far from cheap, but Castelli claims that it offers even better aerodynamics than last year's San Remo speedsuit, which was pretty damn aero. To restore the natural order of things, therefore, this year's San Remo incorporates the latest iteration of this jersey. Mat tested it recently and was impressed by the combination of comfort and performance, so how does the jersey fare on its own?

I tested an XL, which appeared almost comically small when I first took it out of the packet. Castelli tend to size a little smaller than some brands, and here the goal is definitely a skin-tight fit, so there's no way I could have got into a smaller size.

The material is pretty stretchy, as it needs to be, and sure enough there was just enough give for me to climb in. There's a decent full-length YKK zip with a Camlock pull, which is A Good Thing, as the tight fit means that there's more stress on the zip than in other less-tight jerseys. I found that the last couple of inches in particular were a bit difficult to close, and needed to coax the sleeves a little further up my (skinny) arms in order to bring the zip pull up to the neck. The zip operated reliably throughout the testing, though.

The neckline is one of the major changes from last year's Aero Race jersey - it is cut low with a minimal collar, like a skinsuit. The goal, Castelli told us, is to eliminate any folds of material in the area behind the neck, where it can disrupt airflow. Once you've poured yourself in you can certainly see the results - it sits very flat on the torso with next to no folds or flaps (assuming that the same can be said of your torso).

"Er, I don't think you should go out in public in that" came the encouraging comment from my other half, the first time I put it on. The combination of ultra lightweight fabric and the extremely close fit doesn't leave a lot to the imagination. Castelli has managed a neat trick, however, as despite being tight this is not a restrictive jersey and is pretty comfortable in use.

When riding, the fabric around the arms and neck sits smoothly against the skin for minimum drag, but I did notice that the jersey would still sometimes bunch up a bit in the area over the belly and chest. This is really where the idealised sphere of perfect posture and wind tunnels deviates from the real world - when you're thrashing on the pedals, grabbing gels from the pockets and so on, no jersey will remain in quite the perfect position.

This jersey does better than most, though. The lower section around the torso - the black bit - has extra compression, with the specific goal of keeping things in the right place, particularly when you've loaded up the rear pockets. As the jersey is so tight, you can't fit as much in these pockets as on some looser tops - certainly you won't be chucking three bidons in there for your teammates up the road.

I found I could just about squeeze in a lightweight gilet in, plus a spare tube, CO2 inflator and my phone, and having done so, they certainly stayed put. Access to the contents of the pockets is a little more fiddly than on some jerseys, simply because this one is designed to be so tight.

I used the jersey in a few races and some longer road rides on hotter days and it felt fast. Castelli claims a saving of 20 watts at 40kph, compared to a normal race-fit jersey. That sounds like quite a lot to me, but I don't have any data to prove or disprove it, and presumably Castelli do. Certainly, when your goal is to go as fast as possible, having a jersey that doesn't flap around must be a good thing.

There are a number of different fabrics used here, with exciting names like 'Velocity Dry'. They're all very fast-drying, so Castelli say the Aero Race 5.0 is also a good choice for cool and wet-weather racing. Relatively-speaking, of course; cool in Castelli speak is 17 degrees or more. I'd go along with this - any colder and I'd probably want something slightly more substantial.

Around the bottom of the sleeves are wide stretchy bands which are very comfortable and do a good job of holding position. Finally there's a couple of reflective tabs on the back, which I am glad to see. They're sewn in, so they won't peel off.

So, should you buy it? Well, if you're not a skinsuit person then this jersey offers you near enough the same aerodynamic advantage when paired with some suitable bibs. You'd probably not pick it out the drawer for an all-dayer - it's definitely race gear - but assuming that you've already nailed the other contributory factors in your drag equation (and you have the money) this might make you a little bit faster.

Verdict

Lightweight, super close-fitting aero jersey to make you a little bit faster, if you can fit in it