Castelli Alpha Doppio RoS Jacket review

The Castelli Alpha Doppio RoS jacket is designed to be a deep-winter top that can handle the coldest temperatures and a good deal of inclement weather, in a single garment.

It replaces the highly regarded Alpha RoS 2, while I’ve remained wedded to my own first-generation Alpha RoS jacket to this day.

I was hoping for small tweaks to the recipe, rather than an overhaul, and that’s what we’ve got.

Castelli would appear to have listened to customer feedback in making the cut a little looser, the Gore-Tex outer fabric has been updated, while the insulating layer is now made of Polartec Alpha fabric.

The only real fly in the ointment is the heady price tag, plus the fact that with any changes to sizing or fit, you’ll never be able to please everyone.

Castelli Alpha Doppio RoS Jacket details and specifications

The Castelli Alpha Doppio RoS jacket sits beneath the Alpha Ultimate in terms of price, but is very similar in its all-winter weather intentions.

The outer-facing panels are made of Gore-Tex Infinium Windstopper 150 fabric.

As I mentioned when this jacket featured in an edition of First Look Friday, the 150-grade fabric is a little thinner than the 205-grade version found on the venerable Perfetto (née Gabba) long-sleeve jacket.

In theory, this should be a little more breathable (but less insulating) on its own, but underneath the Alpha Doppio there's a Polartec Alpha liner to compensate (and then some).

This liner is separate at the front, and so features its own zip to customise how much insulation you’re getting on your chest and belly.

However, it’s permanently attached over the shoulders, at the back and down the front of the arms. When fully zipped up at the front, only the side panels and backs of the arms are ‘uninsulated’.

The insulation is claimed to be effective down to -5°C and Castelli says it should remain breathable up to 10°C, helped in part by the open-bottomed flap on the upper back.

The pocket formula remains fairly static compared to the previous generation – three cargo pockets are installed on the back and a zipped valuables pocket lives on the front.

These cargo pockets have little reflective tabs for added visibility in low-light conditions, each with three small drainage holes cut out.

The collar and cuffs are double-lined. The inner layers are fleece-lined for comfort and designed to stop draughts sneaking in, while the outer layers largely overlap with the more weather-resistant Gore outer fabric.

At the wrists, this design is also said to create an interlocking interface with the cuffs of winter gloves.

At the bottom, the dropped tail is lined with a flat silicone gripper, which extends right around the waist.

The outer zip is covered by an additional draught guard, but there’s no zip garage at the neck line.

Overall, Castelli has eased the cut of the Alpha Doppio in a similar fashion to its latest Perfetto jackets – it’s now a little looser across the body, shoulders and arms, in order to fit a wider range of riders without having to shop up a size.

Whether you prefer this will be down to your body shape and personal preference. Unlike the Perfetto RoS and its application, where I slightly prefer the old slimmer cut, here I find the extra space a welcome boon for long-ride comfort.

The price will be prohibitively expensive for many, though – at £350, it’s £60 more than the previous-generation Alpha RoS 2 at launch.

That said, there is an argument to make that the Alpha Doppio could be all the winter cycling jacket you ever need, before you’re donning arm warmers and a gilet for springtime.

The Doppio RoS is available in red (as tested), black, ‘Rover’ green and orange, in a wide range of seven sizes (XS-3XL).

Castelli Alpha Doppio RoS Jacket performance

The Castelli Alpha Doppio RoS jacket is impressive in changeable winter weather, excelling especially in freezing temperatures.

On my coldest test ride, measuring 0ºC on my Garmin bike computer (and far below this in windchill factor), the Alpha Doppio jacket kept me warm with just a Merino wool baselayer underneath.

The Polartec insulation worked brilliantly, while it also let a decent amount of moisture through to the Gore-Tex outer layer, which in turn appeared to let a good deal out.

Riding steadily with my heart rate well under control, I was able to stay comfortable and avoid saturating my baselayer.

In mid-single-figure temperatures, it’s easy to get a little overheated and damp when tapping out a tempo (especially, I found, when ambient humidity was higher), but the same could be said for many deep-winter jackets.

Having the inner liner unzipped goes some way to addressing this, but once the temperatures start reaching towards the upper end of Castelli’s claimed range, I found myself looking for an alternative outer layer.

I’m also very impressed with the draught-tackling seals at the wrist and neckline – I never felt a need to wear a neck warmer (contrary to normal) because the neck is so well lined, while the cuffs worked well with Gore C3 Gore-Tex Infinium Stretch Mid gloves.

Thicker-cuffed gloves don’t work quite as smoothly, perhaps understandably.

In the rain, the Gore-Tex Infinium fabric does a great job of keeping ingress at bay, while the DWR (durable water repellent) treatment is effective at beading showers off.

Exposed to heavy prolonged rain, I didn’t detect any water coming through the fabric or seams, but noticed the surface fabric wetting out after a while.

While this didn’t allow water in, it starkly reduced the jacket’s breathability and caused a lot of moisture to build up inside, almost soaking my baselayer.

However, it’s worth noting that technical fabrics such as Gore-Tex, while able to breathe and resist water, can seldom do both as effectively at the same time.

While it performs better than my original Alpha RoS jacket in the rain, this could be down to the fact that the original DWR treatment on my old jacket has degraded over the years.

A DWR reproofing treatment, while usually not as effective as factory-applied treatments, may well be a far better-value option for those who already own one (or one like it) that’s still in good general condition.

For those who don’t, and are considering the Alpha Doppio RoS jacket anew, the £350 / $399.99 price tag is incredibly expensive, even if the performance in poor winter conditions is impressive.

In Europe, it’s slightly cheaper at €319.95 (equivalent to around £275 / $350 at the time of writing).

In terms of similarly designed competitors, Castelli also makes the even more expensive Alpha Ultimate (£390 / $449.99), which Oscar Huckle rated very highly, and the lighter and slightly cheaper Alpha Flight RoS jacket (£290 / $319.99 / €269.95).

You could also consider deep-winter alternatives such as the Assos Mille GT Ultraz Winter Jacket Evo (£300 / $315 / €260).

That said, it’s clear across the board that to combine water resistance and thermal capability in one garment, while incorporating well-regarded brand names such as Gore and Polartec, you'll always be required to shell out a fair wedge of cash.

Castelli Alpha Doppio RoS Jacket bottom line

The Castelli Alpha Doppio RoS jacket is a great one-punch answer to the worst winter conditions.

While a dedicated shell is probably more waterproof, it offers enough protection in this regard to be used in all but the heaviest and most prolonged wintry rain.

In the coldest weather, it’s almost peerless.