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The Castelli Alpha RoS 2 Jacket is an exceptionally good windproof for cold weather with a few tricks up its sleeve – literally, in one case – that add to the performance.
Ash reviewed a previous version of the Alpha RoS a couple of years ago and praised it as an all-in-one winter jacket that's hard to beat. I agree. It has been updated with a handful of genuinely useful new features that I'll come to in a mo.
The exterior is made from Gore-Tex Infinium Windstopper 150 which, as the name suggests, prevents cold air from blowing in. You don't need me to tell you how important that is when the temperature is close to zero and you hit the longest, fastest descent of the day. It stops that wind chill wrecking your fun.
There are a couple of other things you need to know about Infinium Windstopper 150. First, it's highly breathable so you don't get that boil in a bag effect when you hit the climbs.
Second, although Gore doesn't call it waterproof, Infinium Windstopper 150 is way more water-resistant than you might expect, a durable water repellent (DWR) coating helping out the internal membrane in this respect. Castelli has added more external taping to the seams over the shoulders than on previous versions of this jacket, but the other seams aren't taped so water can creep through. Even so, the Alpha RoS does a great job of keeping road spray and short showers out. You can't dispense with a waterproof shell if heavy rain is forecast, but I've stayed perfectly dry in changeable conditions.
Another crucial element of the Alpha RoS 2 is the clever double-layer construction. Opening the front reveals inner panels that attach at the sides of the jacket and zip together in the middle. Effectively, it's like having the front half of a gilet attached in there (check out the pics – they explain it far better).
This inner layer is fleecy polyester that provides extra insulation. The same fabric is used inside the sleeves, extending around about two-thirds of the circumference of your arms.
This double layer at the front gives you a few different options. You can have both closed up when you want maximum warmth and protection. You can open the outer but leave the inner done up when you hit a climb and want to let humid air out and cool air in. You can even push the inner layer to the sides and zip up the outer if you want that windproofing but don't need so much insulation on your chest.
The bottom line is that this structure isn't a gimmick, it works really well, allowing you to adjust things according to the conditions, the terrain, and your riding intensity, without the jacket as a whole flapping about or the need to stop and add/remove layers.
One new feature with this incarnation is the double-layer cuff which is similar to designs you'll find on quite a lot of outdoor coats. Essentially, inside the Infinium Windstopper 150 layer there's a second, more stretchy cuff. The inner cuff goes closest to your arm, tucking inside the top of your glove, and then the Infinium Windstopper 150 layer goes on the outside. The idea is that any water that runs down the outside of the Windstopper fabric doesn't simply get funnelled into the top of your glove. It works really well so it's worth taking a few seconds at the start of your ride to get everything arranged properly.
Up top, the neck is tall with a comfortable fleecy section around the back, while stretchy panels at the waist – made from the same fabric as the inner cuffs – ensure a close fit in that area, and a silicone gripper holds the hem in place.
The Infinium Windstopper 150 itself is also stretchy – particularly across its width – to offer a close fit that doesn't feel at all restrictive or uncomfortable whether you're sitting upright or down on the drops.
I've been using this jacket in all kinds of winter conditions, and it has put in an exceptional performance throughout. Castelli says the Alpha RoS has a temperature range of -5°C to 10°C. The coldest I went in this jacket was -2°C, but it was a really blowy day and the wind chill meant it was considerably colder, so I'd say Castelli is about right. Of course, you can always vary what you wear underneath according to the temperature too.
Castelli has made changes to the pockets on the latest version of the Alpha RoS. The small pocket at the front of the hip has been moved to the side panel which means you can put a little more inside without it becoming annoying when you pedal. Keys and money are fine in there although I must say that the waterproof zip hasn't been the most eager to open and close. It has been a bit of a struggle on occasion.
A bottom panel has been added to the rear pockets so there's now more volume inside. I didn't really notice in use because I tend to travel light anyway, but the extra capacity is there if you need it. The pockets still have laser-cut drainage holes in the bottom to stop water that rolls down your back accumulating in there.
Of course, £290 is a lot to spend on a cycling jacket, although the Assos Mille GT Winter Jacket Evo we reviewed recently was £225 and Rapha's Classic Winter Gore-Tex Jacket is £270.
What I would say, though, is that the Alpha RoS 2's double-layer construction makes it incredibly versatile so you're getting more for your money than you might think. Plus, anything that makes riding in cold weather more comfortable has to be worthy of consideration. As long as you don't come off and rip it, this jacket will last you several years.
Overall, the Alpha RoS is a great design. The premium-quality fabrics and double-layer construction mean you can stay comfortable across a range of winter temperatures – even freezing and below – without getting too sweaty when you hit the climbs. It'll keep you dry through showers too, meaning that you don't need to mess around with a waterproof shell unless you encounter heavy rain. The all-round performance really is something special.
Exceptionally versatile winter windproof jacket that's warm and highly water resistant
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road.cc test report
Make and model: Castelli Alpha RoS 2 Jacket Mens
Size tested: Large
Tell us what the jacket is for and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
Castelli calls the Alpha RoS 2: "[Our] ultimate jacket, bringing warmth, breathability and a high level of rain protection along with a soft, comfortable fit. With a fresh update in its third generation, this jacket leads the way in demonstrating how a winter jacket should perform."
If you'd like more detail, Castelli offers a huge writeup.
"This jacket is exactly what we think the perfect winter jacket should be. We started with a list of things we didn't like about the current jackets and set out to solve them''and in the process make our best jacket ever.
"The first issue to resolve related to moisture management. Even the best of the currently available fabrics provide a good level of breathability but can't keep up with the sweat generated during high-intensity riding. So we invented a double-layer construction that allows you to open an outer wind-protection layer while keeping the insulation layer closed and thereby allowing airflow inside the jacket to evacuate moisture while avoiding direct contact with the skin.
"On a long climb we'll completely open the outer layer to allow moisture to escape, and when we start the descent we close the outer layer and are completely dry inside. It works so well that sometimes it feels like magic. New for this year is a softer, warmer 3D insulation-layer fabric that provides better warmth, moisture management and fit.
"Next we focused on the openings: neck, waist and, most of all, wrists. The neck comes up high and is shaped to move with you, whether you're standing or in an aero position being a January hero and attacking your mates.
"For the waist we've created a stretch layer with a silicone bead that lies flat and completely seals out wind without bunching or riding up.
"New for this year is a brand-new double-layer wrist opening with an inner layer to go under your glove that seals tight to your wrist, and an outer layer that goes over your glove so that any rain will roll down the outside of the glove and not end up inside.
"Of course, the ultimate jacket will also hold up well in wet conditions, so we used Gore-Tex Infinium WIndstopper fabric along with waterproof seam taping on critical seams around the shoulder. Other seams are hidden out of direct water flow, and the water-repellent treatment on the fabric is sufficient to prevent most moisture from entering. We call it essentially waterproof, using our own subjective judgment to find a balance between water protection, breathability and comfort. It doesn't mean that no drop will ever come in, but we do longish rides in real rain and stay completely dry.
"All these features make it a favourite of the Team Ineos riders, and the most versatile performance jacket for cold-weather training we've ever created."
Castelli lists these features:
Rain or Shine engineering makes this our best jacket ever for dry conditions while also providing significant rain protection
Gore-Tex Infinium Windstopper 150 fabric for wind protection with high breathability and effective rain protection
Reduced seaming with seam sealing on shoulders reduces chances for water to enter through stitching
Double-layer Alpha construction separates insulating layer from wind/water barrier to let you better regulate ventilation
Water-resistant YKK Vislon zipper slides easily for better regulation of airflow
Raw-edge waist with silicone gripper lies flat and seals out wind
Double-layer cuff integrates with glove to prevent cold wind or water from entering at wrist
Stretch fabrics with advanced patterning make for excellent close-to-body fit that still accommodates a wide range of body types
3 rear pockets with reflective laser-cut drain holes
Zippered secure side pocket for valuables
-5°-10 °C / 23°-50°F
Tell us some more about the technical aspects of the jacket?
Gore-Tex says that its Infinium Windstopper garments are totally windproof, water-resistant, and very breathable, and the performance bears that out.
Gore-Tex says, "Created using an ultra-thin protective layer laminated to a lightweight textile, Gore-Tex Infinium Windstopper products are totally windproof. Although textiles such as microfibers, closely woven fabrics and many fleece materials are often termed windproof, even light winds can penetrate most of these fabrics, making you feel chilled and uncomfortable.
"By Gore's standards, a fabric can only be considered truly windproof if its air permeability is 1.0 cfm (< 5 l/m2/s) or less. It's a standard that our products easily meet.
"The membrane technology in Gore-Tex Infinium Windstopper products has billions of pores that are 900 times larger than water vapour molecules, so even though wind can't get in, moisture from sweat vapour can easily get out.
"In addition to the GORE membrane technology, a durable water repellent (DWR) treatment is applied to most of these products. This penetrates a jacket's outer fibres, lowering the surface tension so that water beads up and rolls off. That means less water accumulation, resulting in less wind chill, and less extra weight."
It's a clever construction, especially at the front where the double-layer design gives you different options to suit the conditions, terrain, and your riding tempo.
The new double-layer cuff design is smart too, stopping water from the sleeves going into the top of your gloves.
It puts in an exceptional performance across a range of winter conditions.
The fabrics have proved to be pretty hardwearing so far. I have a previous version of this jacket from a couple of years ago and that one is still looking good too, including the zip which is good news because it's a big problem if that goes.
Windstopper fabrics aren't intended to be fully waterproof. Rain can get inside this jacket eventually – you still need to carry a waterproof jacket if full-on rain is forecast – but water from spray and short showers beads up and rolls away.
The Windstopper fabric isn't as breathable as a non-membrane fabric, obviously, but it is impressively breathable for a windproof fabric.
I found the fit to be excellent – slim with enough stretch to prevent any rucks or ripples.
As described on Castelli's size chart.
The double-layer construction adds a little weight, but I'm not looking to save grams in a winter jacket, I just want it to keep me comfortable in various conditions.
I've found it comfortable in a variety of different conditions.
This is one of the higher-priced winter jackets we've reviewed, but the fabric tech, the construction, and the performance are all exceptional.
How easy is the jacket to care for? How did it respond to being washed?
You wash it in the machine at 30° and it comes out fine.
Tell us how the jacket performed overall when used for its designed purpose
Exceptionally well across a range of winter temperatures; it copes with showers well too.
Tell us what you particularly liked about the jacket
The versatility of the double-layer front, and the performance of the Windstopper fabric.
Tell us what you particularly disliked about the jacket
It's definitely worth the money, but paying this amount on a cycling jacket still hurts.
How does the price compare to that of similar products in the market including ones recently tested on road.cc?
The Assos Mille GT Winter Jacket Evo we reviewed recently was £225, and Rapha's Classic Winter Gore-Tex Jacket is £270.
Did you enjoy using the jacket? Yes
Would you consider buying the jacket? Yes
Would you recommend the jacket to a friend? Yes
Use this box to explain your overall score
The performance is exceptionally good, and that's definitely worth paying for if you ride year-round whatever the conditions.
About the tester
I usually ride: My best bike is:
I've been riding for: Over 20 years I ride: Most days I would class myself as: Expert
I regularly do the following types of riding: commuting, club rides, sportives, general fitness riding,
Mat has been in cycling media since 1996, on titles including BikeRadar, Total Bike, Total Mountain Bike, What Mountain Bike and Mountain Biking UK, and he has been editor of 220 Triathlon and Cycling Plus. Mat has been road.cc technical editor for over a decade, testing bikes, fettling the latest kit, and trying out the most up-to-the-minute clothing. We send him off around the world to get all the news from launches and shows too. He has won his category in Ironman UK 70.3 and finished on the podium in both marathons he has run. Mat is a Cambridge graduate who did a post-grad in magazine journalism, and he is a winner of the Cycling Media Award for Specialist Online Writer. Now over 50, he's riding road and gravel bikes most days for fun and fitness rather than training for competitions.