Castelli Nano Flex Pro Omloop thermal bib shorts review

The extra-long Castelli thermal shorts put to the test

Castelli Nano Flex Pro Omloop thermal bib shorts
Cycling Weekly Verdict

The Castelli Nano Flex Pro Omloop thermal shorts are clearly a very high-quality piece of kit and one that will deliver almost everything it offers. The fit around the knee could be an issue for some, and could require a lot of trial and error to get the right fit.

Reasons to buy
  • +


  • +

    Lightweight and breathable

  • +

    Great rain protection

  • +

    Really comfortable

Reasons to avoid
  • -

    Length towards the knee could be difficult to get right

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I'm a big fan of thermal bib shorts. Paired with a decent pair of leg warmers, there's nothing more snug on winter or early spring rides and I very often opt for them over a pair of regular bib tights. So let's see how the Castelli Nano Flex Pro Omloop thermal bib shorts fare.

The Castelli Nano Flex Pro Omloop thermal bib shorts presented a slightly alternative take on thermal shorts that I've not encountered before.

Unlike other thermal shorts, which stick to similar shapes and seams as a summer equivalent, the Castelli Nano Flex Pro Omloop thermal bib shorts immediately stand out because of their extra length and lack of seams at the leg opening.

In theory, this'll create a warmer and ultimately better ride. The cut of the legs is longer at the front than at the back, and the shorts are designed to reach just to the top of the kneecap at the front without creating discomfort at the leg bend behind.

In practice, this seems difficult to consistently get right with standard sizing. As a tall rider, I was quite surprised to find the medium size I was wearing came down as far it did. While it wasn't overly intrusive, I would occasionally experience some bunching behind the knee, and I'd be surprised if shorter riders didn't struggle to find the perfect fit from the range of sizes available.

I almost never wear a pair of thermal shorts without leg or knee warmers, but if I did decide to go bare legged with a pair, it wouldn't be these.

Just standing in my bedroom with them on I really didn't like the look of them without warmers. If you're not a fan of three-quarter-length bibs or knee warmers though, and you can tolerate the look, these will do a good job in providing some extra warmth.

Aside from this, there are really very few negatives to report about the Castelli Nano Flex Pro Omloop thermal bib shorts. I've found Castelli to be one of the more consistent brands through its range of shorts and these are as good as any I've used before.

Castelli Nano Flex Pro Omloop thermal bib shorts

They come with a Progetto X2 Air seat pad, a really reliable and comfortable chamois I've always had good rides on. Moreover, the mesh bib straps are comfortable and add to the quality fit of these shorts.

They're fleece lined and felt such good quality on first inspection that I was a bit worried about how they'd come out in the wash. Fortunately, a cold wash at 30°C with the rest of my kit saw them come out as good as new.

They feel wonderfully warm on rides and the Nano Flex fabric means they fit really nicely around your body shape. Minimal seams also means there's no extra constricting: I've found other shorts like the Rapha Pro Team Thermal II shorts can be quite compressive in certain areas.

I only rode these in light rain but they appeared to do the job well in keeping out the wet, beading the water on top of the outer and not letting it soak in. In that respect they still maintained breathability with a lovely lightweight feel.

I'll definitely put these shorts into my winter and bad-weather wardrobe and at £110 RRP (available for much less if you shop around), I reckon you're getting a very good pair of thermal shorts that should last long-term.

That said, there could be some real trial and error in finding the right length and fit around the knee along with getting the rest of the size right. If you can get it spot on though, you'll have a really high-quality pair of shorts to see you confidently through the cold and wet.

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