Castelli Alpha ROS 2 Jacket Review

By Brandon Bilyeu

Hot!

• Windproof front and breathable back construction
• Front facing insulation for warmth
• Excellent temperature control due to zippers, vents, and materials
• Highly water-resistant material with strategically placed taped seams
• Snug fit with just enough room for layering
• Three standard rear pockets plus one zippered

Not!

• No truly hi-viz colors, but a couple non-dark colors are available
• Sealed wrist openings can make for hot arms
• Expensive

Cost: $370

How obtained: review sample from company

Available: online, retail

Colors: Light Black, Dark Gray, Savile Blue, Pro Red, Fiery Red

Website: Alpha ROS 2 Jacket

RBR Sponsor: no

Tested: 20+ hours

Sizing: S-XXXL

Reviewer Measurements and Fit Comments: 5’10” (178cm), 150 lbs (68 kgs), 33″ (84cm) waist, 38” (96.5cm) hips, 33″ (84cm) inseam, 37″ (94cm) chest. I tested size Medium and the fit was very good, form fitting but enough room for layering underneath. Front waist seems a little long and bunches up when bent over on the bike. 

Castelli Rain or Shine (ROS)

Castelli’s Rain or Shine concept is to design cold weather kit for dry conditions and then add functional rain protection that doesn’t detracted from the dry performance, namely don’t be a steamy hot mess like most full-on rain jackets. The Alpha ROS 2’s dry and cold performance is achieved with a combination of GORE-TEX INFINIUM WINDSTOPPER 150 fabric and strategically placed 3D waffle insulation. The insulation is placed on all forward-facing surfaces of the jacket behind the WINDSTOPPER and the combination does a great job of stopping all the wind and holding in heat. 

The difference in front and rear construction is most obvious on at the start of a cold ride before you are fully warmed up and your front feels nothing from the icy wind, but you can feel some cold on your back. For moisture management the back lacks the heavy waffle insulation and instead has a thin mesh liner (similar to a base layer) that holds some heat and makes for excellent breathability/wicking so you stay dry in addition to warm. 

To maximize moisture management and temperature control Castelli separated the WINDSTOPPER and insulation layers over the chest. Unzip the wind protection layer and underneath the insulation still covers your chest with its own zipper. This dual layer system, combined with vents on the upper back, gives you a massive amount of control over temperature and moisture. The images below of the jacket worn inside-out are a great visualization of the whole system showing the locations of the insulation (red).

Rain protection is provided by a DWR coating on the outer WINDSTOPPER fabric.  To further improve water resistance Castelli used hidden seams and taped the seams on top of the shoulders (red tape on blue jacket shown below). While only water resistant I found it to be very effective against snow, light drizzle, and road spray. Castelli calls it “essentially waterproof”, but when it’s threatening to rain and the temperature is almost freezing it’s probably best to bring a back-up shell that is 100% waterproof.

ROS = Super Comfortable Winter Jacket

I run hot and sweaty so for me winter riding is a constant battle to stay warm, but not overheat and get soaked by sweat. This requires clothing that provides wind protection, insulation, breathability, and venting. It also requires constant attention on my part to make sure I am frequently adjusting the thermostat knob known as the zipper. I’ve worn lots of jackets over the years and the Alpha ROS 2 Jacket is one of the best at keeping me warm and dry.

Castelli rates the Alpha ROS 2 for 23 to 50 F (-5 to 10 C) and I have worn the jacket in perfect comfort in the mid-20s with only a thin base layer underneath. At the other end this jacket is too warm for me at 50 degrees, but temperature ranges are very personal. The dual zipper system works great for dumping heat/moisture and adjusting the level of insulation. When unzipping other jackets, the icy wind directly on a base layer covered chest can be locally very cold while the rest of the torso is warm. But the ROS system insulation layer cuts some of the wind to keep the torso temperature more even. The outer zipper has a big pull tab for ease of use, but the inner insulation zipper has only a small pull tab that can be a little challenging to grasp with thick winter gloves. I easily fixed this by adding a bit of string, but it’s a simple detail that Castelli should have noticed during cold weather testing.

A high and soft double collar keeps the neck warm without the need for a buff/neck gaiter and a stout waistband with grippers seals out cold air from below. The dropped tail provides good rear coverage, but the front waist is also dropped quite low and bunches up when bent forward over the bike. The sleeves are plenty long for reaching the drops and the wrists are well-sealed with an inner and outer cuff creating a labyrinth to keep wind and water out. The sealed wrist does mean no airflow in the sleeves and this is the only place where the jacket got a little sweaty for me. An adjustable wrist opening or small zippered vent would improve air flow and comfort here.

Finally, the Alpha ROS 2 does have external rear pockets so you can access your goodies without opening the jacket and losing the precious heat. Three standard pockets are good sized with moderate stretch and drain holes with reflective accents are included for wet rides. There is a fourth zippered pocket on the left side for valuables, though not deep enough for today’s big phones.

Bottom Line

The Alpha ROS 2 is unquestionably an expensive jacket, but also unquestionably good at keeping you warm and dry on very cold days. The layered design and superb breathability/venting provides comfort even for heavy sweaters and high intensity riding.