Specialized Trail Alpha jacket review – hot but not sweaty

We’ve been testing Specialized’s Trail Alpha Jacket for a couple of years and it’s proved one of the best biking jackets available in all sorts of situations. That’s primarily down to the Polartec Alpha fabric but also a cut that works on and off the bike or for mixed-use bikepacking. The reduced price for this year makes it comparatively good value too.

Design

The Trail Alpha looks like a lot of other lightweight sports jackets. The cut appears simple at first with squared-off shoulders and a slim/casual fit. The open collar doesn’t have a hood, the sleeve cuffs are just short elastic sections and there’s no snugging cord on the hem. The front zip is two-way with a beard protector flap at the top and you get zipped hand pockets as well. There’s also a zip above the right hip which makes it easier to quickly draw your sidearm or reach around to the back pockets in a jersey or SWAT shorts underneath. The men’s version comes in black (UK) and crimson, slate grey, and oak green in S-XXL, but women get the choice of maroon, black, or crimson in XS to L. All have small reflective S logo and spine stripe details but are plain otherwise.

What separates these jackets from the pack is the use of Polartec Alpha fabric on the inside of the shell everywhere except the underarms and back of the sleeves which are stretch microfleece. This sparse coverage of tufted grey fleece doesn’t look that cozy (in fact it looks a bit threadbare and second-hand even when brand new) but the performance it gives is genuinely remarkable.

Performance

Like most fleeces, it multiplies its warmth by trapping warm air between under layers and the extremely light and stretchy windproof outer shell. It does this remarkably well too so you’ll need to recalibrate your warmth expectations if you’re not going to roast in it. Note that I didn’t say ‘boil in it’ because the other thing Polartec Alpha does brilliantly is wick sweat from skin or base layers and spread it over the outer shell for evaporation. 

Specialized have resisted the temptation to add a DWR water-repellent coating to the shell too. As a result, water soaks through quickly but it’s rarely obvious from the inside. Lack of surface treatment maximizes sweat vapor and drying transfer outwards as well. This means your core stays much drier than normal so you’re not losing heat through damp base layers or wet skin. The uninsulated underarm and arm back panels help heat management too so I’ve been comfortable from hard climbs on milder days and on sub-zero sleet and snow days with significant wind chill. 

You will need a Buff or similar neck tube to seal the open collar and gloves with a decent cuff to seal the open sleeves on the worst days, but otherwise, its weather sealing is awesome. The fact it dries quickly is a real bonus for avoiding chill on changeable weather days and hand pockets are always a win when you’re waiting around. The slow-drying, cold elastic cuffs are a contrast to the rest of the coat, but at least they prove just how well the Polartec Alpha works. They seem to have sorted out the rapid stink-up issues of early Alpha jackets I tested too, as there was nothing noticeably anti-social about it even when I wore it repeatedly for day after day of riding. That obviously plays well in a bike-packing format where the styling is a win too.

The shell fabric is also very quiet and natural in feel and the sleeve length and cut give good coverage without being restrictive. The lack of flapping fabric will also suit faster MTB/gravel riders. Our sample was on the slim side for a medium though so check fit if you're not. It’s well-priced compared to Giro’s Cascade Polartec Alpha option and balances warm and cold areas better for most people too. 

The side zip can be a nasty cold shock on bare skin when pulling it on though and the jacket is so stretchy its usefulness is definitely debatable.

Verdict

Specialized’s Trail Alpha Jacket is an almost perfect example of why I’ll always tell people to choose a tech fleece/softshell jacket over a waterproof one. While it works brilliantly on the bike in a very wide range of weather it doesn’t look weird when you’re not riding either. That adds versatility to an already good value price and confirms it as a superb investment if you can afford it. At the time of going to press it was half price in the US and the women’s version was half price in the UK too.

Tech specs: Specialized Trail Alpha Jacket

• Price: $225 / £150 / €170
• Sizes: Men S-XXL, Women XS - L
• Men's colors: Black, crimson, slate grey, or oak green 
• Women's colors: Maroon, black, or crimson
• Weight: 330g