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Giant's Proshield MTB Jacket offers good casual looks, a hood that engulfs the biggest helmets and great breathability when dry. But the boxy cut, awkward zips and lack of water-repellent coating means the outer shell soaks out quickly, and then can't breathe well at all – leaving you soaked and chilled in sweat.

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In technical terms, the ProTextura Plus fabric has a rating of 10000 g/m2/24hr, and the proofing is 10000 mmH2O. In more familiar terms, it's waterproof for around an hour in heavy rain, and then you get wet.

It breathes well and resists moisture build-up in the dry, but with no DWR coating to bead water and encourage it to roll off, the outer fabric is vulnerable to becoming saturated. Once that happens, it can no longer vent the vapour from inside, and breathability plummets. Your trapped moisture condenses and trickles down. You'd swear the jacket leaks.

It also takes a long time to dry out. The Proshield MTB has ventilation holes and zippered arm pits, but these don't solve the problem. Plus, while the seams are taped throughout, some areas on ours weren't completely sealed down. General wear and tear is unlikely to improve that situation.

The hood is absolutely massive and will happily cover any lid you choose. It’s detachable via a zip and velcro tabbing - good as it tends to billow like a galleon's sails, but bad in that sudden downpours have you fumbling to zip it back on. It would be better to be able to secure it down rather than take it off, though it does at least have drawcords to pull it in somewhat.

The armpit vents are too short, and not easy to open in gloves as they use a small plastic tab rather than a cord. Meanwhile the two front pockets are plenty big, but again suffer from the small tab. There are useful reflective areas on the sides and front, though they're small too.

The zips are waterproof and live behind protective fabric flaps, while the main zip also gets magnets to hold the flap shut. This works well, and beats Velcro by leaving nowhere for filth and fluff to build up.

The cuffs actually do use Velcro – and elastic – for adjustment, and it's a straightforward design that does the job.

At the bottom, the hem can be cinched in via an elasticated cord and toggle, but the square shape of the jacket means there's a lot of fabric to get bunched up if you do. The whole thing also tends to ride up the back unless you're wearing a pack.

That boxy cut and the stretchy fabric means your movements are never inhibited, though it's best worn over long-sleeve tops as the interior feels clammy on bare skin, even when dry.

The Proshield is fine in brief showers, but prolonged rain overwhelms it. And despite the windproofing helping you retain some heat, a couple of hours' wet riding is enough to leave you feeling chilled, damp and unhappy.

It's fine for short showers or mist, and the breathability is really good when it's not raining, but that defeats the point. Yes, it packs down well, and can be stashed for emergencies, but so do plenty of other jackets that work far better.

The harsh truth is, I can't think of any reason to recommend Giant's Proshield MTB Jacket, as it just doesn’t stack up against the competition for performance, fit, build or even – given its flaws – price.

• www.giant-bicycles.com

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