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Castelli Nanoflex bib tights



Water-resistant bib tights for wet and changeable conditions; a decent price too.

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

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Castelli's Nanoflex bib tights are a water-resistant option for wet and changeable off-season weather, and that means a lot of the time in the British autumn/winter.

Castelli's Nanoflex is clever stuff. It feels like a normal Roubaix-type fabric – it's stretchy, it's warm, it's breathable – but it is also water repellent thanks to a silicone 'nanotechnology treatment'. Water beads up and rolls off the surface. Really, it does.

That's not to say that Nanoflex is entirely waterproof – it's nothing like GoreTex, for example – but I was out on a ride this past weekend, for example, and it started hoofing down. After a few minutes of pretty heavy rain, I glanced down to see thousands of little water droplets on the surface of the Nanoflex tights. Yes, some water had got in, but not nearly as much as would have got through normal tights, so I was a lot drier and warmer than I'd otherwise have been.

The really good bit is that it's all benefit; there's no downside. A hardshell waterproof jacket or overtrousers will stop rain getting in but they'll also compromise breathability to some extent. That's not the case with Nanoflex. It's a lot like a thousand other fabrics used for cycling clothing, just with the added benefit of being water repellent. You're not compromising on other properties here.

We've reviewed plenty of Nanoflex items on before, so check them out too. We've found that the water repellency will gradually diminish over time but you can restore it to virtually as good as new by ironing the fabric periodically. Honestly! Just don't let anyone catch you ironing your cycling kit. They think you're crazy enough already.

The seatpad is Castelli's own Kiss3 design. It's not their top level pad (that's their Progetto x2 which really is a bit special) but it's still pretty darn good. The Kiss3 looks basic but that's largely because Castelli haven't stuck graphics all over it shouting about the various features. It actually uses two different densities of padding and the thickness varies in different areas too, being at its greatest underneath your ischial sit bones.

The pad is stretchy enough to mirror your movement as you pedal and the soft, brushed microfibre layer next to your skin has an antibacterial treatment. It's a really good pad on the quiet, and I didn't give saddle comfort a second thought even on big weekend rides.

Castelli haven't gone for loads of different panels here '' quite the reverse. Each leg is one piece of fabric with a single seam down the back. I can't say I particularly noticed that in use, and I didn't get any trouble from that seam, even though it's not flat-lock stitched. Castelli say they've kept the seams to a minimum in order to maximise water resistance, and that seems like sound thinking to me.

The bib section is a light, breathable mesh with wide shoulder straps to reduce the pressure, while at the bottom of each leg you get a YKK ankle zipper with a camlock puller that locks in place and a reflective flap that sits over the top.

The ankle grippers, which Castelli call Giro3, are super-stretchy. If you're not wearing overshoes, they sit right against your ankles the same as normal, but you can also position them over the top of overshoes rather than tucking them inside. Why? You don't want the water that the Nanoflex won't let in simply rolling down the outside of your tights and funnelling into your shoes. Again, it's good thinking and it does work.

The Nanoflex tights provide a level of warmth similar to other Roubaix-type tights, with the addition of that water resistance. Castelli give a temperature range for these of 6-18°C. Their guidelines are usually pretty accurate, I reckon, but even I wouldn't be wearing fleece-backed full-length tights at 18°C and I'm famous for getting cold at any opportunity. About 6-14°C, I'd say.

Don't get these confused with Castelli's Fluido bib tights from last year, by the way . Those tights did have Nanoflex panels but they were different in several other ways.

The are also available in a bib knicker (three-quarter length) version for £95, and as bib shorts for £85. We've not used either but they both use the same Kiss3 seatpad.


Water-resistant bib tights for wet and changeable conditions; a decent price too.

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Make and model: Castelli Nanoflex Bibtight

Size tested: XL, Black, 2 sent

Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

Castelli say, "Our Nanoflex water-repellent fabric is one of those fabrics that seems miraculous. On a dry day it's as warm and breathable as our normal Thermoflex fabric, but when it rains the water just runs off, thanks to the five-phase nanotechnology treatment. We've used an innovative construction that minimizes seams to keep you as dry as possible. While it's not 100% waterproof, it's the best solution we've ever tried for staying comfortable in any condition.

The KISS3 seat pad features an anatomic shape to conform to your body and ultimately increase your comfort. A continuously variable thickness eliminates the odd sensation of 'thick here, thin there' that you may have seen before with a dual-density pad. The brushed microfiber cover cuts down on chafing and features a bacteriostatic treatment to reduce the likelihood of saddle sores.

Bibtight and knicker: GIRO3 grippers position the tight and seal around the shoecover, while on the knicker the grippers help the fabric stay put without binding. The mesh bib straps help transport moisture to the jersey and make sure the waist stays where it's meant to be. Reflective Castelli print and reflective tape zippers make you more visible in low-light conditions."

Tell us some more about the technical aspects of the product?

The Nanoflex will lose its water repellency but you can rejuvenate it by ironing lightly. Seriously, it works!

Rate the product for quality of construction:
Rate the product for performance:
Rate the product for durability:

As mentioned, ironing the Nanoflex fabric will renew its performance. The printed-on graphics don't last as well as the other features of these tights.

Rate the product for comfort, if applicable:

The seatpad isn't quite as comfy as Castelli's top-level option, but it's not far off.

Rate the product for value:

These are good value. You get high-performing tights regardless of the water repellency. With that added into the equation, the value is high.

Tell us how the product performed overall when used for its designed purpose

They do exactly what is promised, so no complaints.

Tell us what you particularly liked about the product

The effectiveness of the Nanoflex fabric, and a very good seatpad too.

Tell us what you particularly disliked about the product

The only thing we find that lets Castelli down a little in terms of quality is the printed on graphics. They crack and age long before anything else.

Did you enjoy using the product? Yes.

Would you consider buying the product? Yes, certainly.

Would you recommend the product to a friend? Yes.

Overall rating: 8/10

About the tester

Age: 43  Height: 190cm  Weight: 75kg

I usually ride:   My best bike is:

I've been riding for: Over 20 years  I ride: Most days  I would class myself as: Expert

I regularly do the following types of riding: commuting, club rides, sportives, general fitness riding,


Mat has been in cycling media since 1996, on titles including BikeRadar, Total Bike, Total Mountain Bike, What Mountain Bike and Mountain Biking UK, and he has been editor of 220 Triathlon and Cycling Plus. Mat has been technical editor for over a decade, testing bikes, fettling the latest kit, and trying out the most up-to-the-minute clothing. We send him off around the world to get all the news from launches and shows too. He has won his category in Ironman UK 70.3 and finished on the podium in both marathons he has run. Mat is a Cambridge graduate who did a post-grad in magazine journalism, and he is a winner of the Cycling Media Award for Specialist Online Writer. Now over 50, he's riding road and gravel bikes most days for fun and fitness rather than training for competitions.

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