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CastelliNanoFlex 2 Bib Short - Men's
Sale 40% Off$59.98 - $74.96

Item # CST008X

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Item # CST008X

Keep the chamois dry.

The insulating warmth and water repellent attributes of Castelli's Nanoflex 2 Bib Shorts are the ideal match for any of the new breed of windproof, rain-resistant super jerseys based on the now-legendary Gabba. Whether worn alone for a bit of fall insulation or to make rainy spring racing endurable or matched with a complementary pair of Nanoflex leg warmers for winter base miles, the Nanoflex Bibs are among the most versatile kit that we own. They don't quite have the second-skin fit of bibs like the Free Aero Race shorts, but the benefits of a dry chamois over the course of a wet ride are impossible to overstate.

The secret to the Nanoflex 2 Bib Shorts' success is hidden subtly in their name. They're made from Castelli's Nanoflex fabric, which is a water-resistant version of Castelli's insulating Thermoflex fabric. Nanoflex is coated with millions of nanofilaments to create a water-repellant surface, compelling rain and road spray to bead up and roll off the surface. Of course, the introduction of those nanofilaments doesn't interfere with Nanoflex's thermal properties, and the brushed interior not only keeps warmth in, but it also wicks moisture away from your skin. The Nanoflex Bib Shorts keep you dry from inside and out, because nothing puts the stop to a cool, damp base mile session faster than the accumulation of clammy moisture on your skin.

The bib straps are made from breathable mesh that won't interfere with your upper-body layering with patches of extra insulation, and compressive, gripping bands at the leg openings maintain water-repelling coverage. The inclusion of Castelli's Kiss Air insert ensures a comfortable cyclist-to-saddle interface with a varying topography of breathable padding and a soft, bacteriostatic cover.



Men's Apparel




















































How to Measure:
For best results, take measurements over your underwear.
Measure under your arms, around the fullest part of your chest.
Measure around your natural waistline, keeping the tape a bit loose.
Measure around the fullest part of your body at the top of your legs.
Using pants that fit well, measure the crotch seam to the bottom of the leg.

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Not made for human bodies

  • Familiarity: I returned this product before using it
  • Size Bought: Large

I am reasonably impressed with the workmanship and quality. I have other Castelli products and have been pleased with them, but recent fitting is quite odd. I have fairly large upper body for a cyclist, and not much of a gut, but slightly long torso, and perhaps slightly shorter thighs (32 inseam, and 42 inch chest). I order a large, and could barely get the straps over my shoulders, and the legs were at my kneecaps. The fit of the short otherwise was quite nice (legs fit suggly, waist and other important parts were quite comfortable. I liked the chamois too. I think these were made for a half-man, half-giraffe.

Castilli Bib Shorts

  • Familiarity: I've used it several times
  • Fit: Runs small
  • Size Bought: Medium

Definitely a cool weather bib short. The fit is a little small, but the comfort of the chamois is perfect. I’ve used these a few times since getting them for Christmas and I’d recommend and would purchase again. However, I live in a warmer climate so probably won’t use them except for a few weeks per year.

Different strokes, different folks!

  • Familiarity: I returned this product before using it
  • Fit: Runs small
  • Size Bought: large

Let me start by saying that Castelli is by far and away my favorite kit in general--but there are outliers for me. I purchased these bibs based and the great reviews and on Castelli's overall quality. However, I have the exact opposite take on their fit as the previous reviewer (and we are almost the same size)! I almost believe that the previous review was for the pro model of Nano bibs, as those are excellent and actually DO have a low waist, THESE BIBS DO NOT HAVE A LOW WAIST--THAT IS EVIDENT IN THE PICTURES. Good luck in the restrooms!! Furthermore, the straps are WAY too tight. The pro version has lycra inserts as the strap tops and that makes them very stretchy/comfortable. The straps on these basic Nano's are not only ultra tight, but the material/hems dig into my shoulders/neck (again not the case with the lycra tops on the pro model straps). The pro model Nono bibs also have a longer leg length (I am NOT talking about the Omloops--those are too long).
And the leg grippers on these are only fair, while the pro version doesn't even have a separate material there--it is entirely their Nano material (i.e., water resistant) all the way down. The pro bibs just have leg grippers attached underneath the Nano material.

simple, great bibs

  • Familiarity: I've used it several times

I used these on a sunny day that started at 53 and ended up closer to 80. They were probably warmer than I needed by the end of the ride but I wasn’t overly hot. What I most enjoyed is that when it was cool at the start of my ride my crotch wasn’t chilly. These are a perfect bib for those days where you don’t need knee warmers but still want something warmer than standard bibs which are almost all quite thin. The straps are comfy and the waist is low which I strongly prefer. The grippers are narrow but they work. I paid $75 which is a great deal although they’re worth the regular $100 price. As usual with Castelli I had to size up to a large. I’m 5’9” and 145 pounds.

Perfect for shoulder seasons

  • Familiarity: I've used it several times
  • Fit: Runs small
  • Size Bought: XL

These are great. I have a million layering options for my upper body, but have struggled to find intermediate options for my lower body. Pairing these with a set of Defeet Kneekers and Slipstreams is my perfect solution for rides down to the mid-forties, but I'll probably wear them up to the mid-sixties. When I got them, I was concerned that they wouldn't suit my needs because they didn't feel hugely thicker than my summer bibs, but modern textiles are amazing. These are up to the job, without a doubt.

A note on fit: these fit a tiny bit smaller than my other Castelli bibs of the same size. I went up one size.

Great Cool Weather Shorts

  • Familiarity: I've put it through the wringer
  • Fit: Runs small
  • Size Bought: XL

These shorts do really well especially in cooler weather with leg warmers. I'm 5'11" and 177 lbs and according to the size chart I should fit into a L but got the XL and they fit good especially over leg warmers. If you have larger quads the leg grippers could be a little bit tight don't get the right size and then wear them over warmers.

Inclement Weather Bib

  • Fit: Runs small

Castelli tends to have much overlapping within the line from item to item, but these are a standalone bib that every rider should consider. The Nanoflex material delivers what it is designed to do- insulate, reduce wind and moisture penetration. When combined with leg warmers, the Nanoflex bibs will give more flexibility and range of motion than a tight and still provide the insulation needed in temps below 40 (for me, at least). The perfect combo with these bibs would be Nanoflex leg warmers paired with a Gabba or Perfetto jersey for a day out in inclement or colder conditions. The Kiss Air chamois does the job and works well with this level bib. I typically wear a medium in Castelli bottoms and purchased that size, but the nature of Nanoflex doesn't allow for as much flexibility as materials used on other Castelli seasonal bibs.

I find these short to work well between 40 to 55 degrees especially with rain in the forecast. I am 5' 6" and they run long in a medium for me. My friend has a pair and problem. They are about an inch longer than most shorts. The gripper is quite large though so I was able to have it shorten and that worked out great. Also good for sub 40 degree cross races.

Excellent, as advertised

  • Familiarity: I've used it several times
  • Fit: Runs small

These really do work at shedding water, as it will bead up and keep you dry far longer than typical shorts. Several times I was able to do longer rides, and with more comfort, than I could have done without such rain-resistant gear (using the leg warmers as well, and Gabba or Perfetto jersey, as well as neoprene gloves).

They run small: I am just under 5'10" 150 pounds and wear medium in most brands, but usually large in Castelli. That is even more true for these shorts, which I think have less stretch or at least less margin for error than other shorts from them.

These shorts are super comfy, great chamois; and the length and fit is excellent (very long for warmth, but no bagginess at the knees). These are top shorts to use in rain and cold weather, and I liked these so much I bought a second pair not long after. I like these in temps from the mid-40s thru the 60s.

My only 'complaint' would be that they aren't warm enough or windproof enough for me when it is really cold, like sub-40. I don't know if Castelli makes a bib short using the Gabba/Perfetto material, but that would be an upgrade in terms of warmth and wind-resistance to this Nanoflex material.

Great shorts for the cold/damp

  • Familiarity: I've put it through the wringer
  • Fit: True to size
  • Size Bought: Large

These are warm shorts, and I am comfortable wearing these with a good pair of knee warmers down to the low 30s. I've worn them in temps in the upper 50s and over heating is not a problem. Road spray and drizzle is kept out completely. They will get soaked if it's properly raining, although are fairly windproof so won't chill you too much when wet. An absolute bargain when on sale at around $70 or less, and I bought two pairs, but I like them so much I would probably pay full price they're that good.

My Favorite BIB

  • Familiarity: I've put it through the wringer
  • Fit: True to size
  • Size Bought: XL

Very Comfortable Chamois

Everyone should have a pair of these

  • Familiarity: I've used it several times
  • Fit: True to size
  • Size Bought: XL

This weight of bib should be a fundamental part of every cyclists' wardrobe. Frankly, I think if we were all starting from scratch, this would be the "normal" weight for bibs and the lycra ones we all wear would be marketed as "summer" bibs. These are basically the same fabric and thickness as the Nanoflex leg warmers. With these bibs, now your upper thighs and butt can get the same insulation you are putting on the rest of your body on those cool to cold days. After one ride in the mid 50's I was kicking myself for not getting these sooner. They get even better as it gets cooler. I still switch over to tights once it hits the 40's but I could see hardier souls taking these plus leg warmers down into the upper 30's. They really shine on those days where I don't wear tights (for me in the 50's) but where regular weight lycra shorts left my hind end feeling very cold. They don't feel any different than regular bibs while wearing them. I've worn them on a few rides that warmed up into the lower 60's and they are not too hot. As for fit, they fit exactly like all my other Castelli bibs.

In Between Bibs

  • Fit: True to size

Big fan of fall/early winter riding when temps drop into the 40's and 50's and no need for full winter wardrobes. The Castelli Nanoflex 2 bib shorts fall into this category, as sometimes a bib tight is too much. The Nanoflex material is fuzzy and warm on the inside with good wind and moisture repellent on the outside. When paired with Nanoflex arm/leg warmers and either a Perfetto or Gabba jersey I feel like I'm ready for the elements and won't overheat excessively, as I can regulate temps by shedding arm and leg warmers. Kiss Air chamois works well with this category of bibs. My only gripe would be fit due to less elasticity of the fabric compared to non-insulated bibs along with a higher waist. I typically take a medium in Castelli bottoms, but could have gone to a large for this reason. Overall, very pleased with function and design of these

Near-Perfect Cool Weather Bibs

  • Familiarity: I've used it several times
  • Fit: True to size

I road these in several recent 70-90mi. days with 40-50deg. temps and some rain.

They are nearly perfect except for one issue: the seam across the back/bottom of the shorts crosses right where my sit bones contact the saddle. During some of the riding I didn't notice it while at other times I kept thinking that it could be causing some irritation. However at the end of each day's ride I did not have any added saddle soreness. Hopefully the thickness & softness of the Nanoflex material along with the thickly-padded chamois will make this seam a non-issue over the long run. However, it's location did unfortunately put a bug in my head about the possible source of some added butt discomfort...and we all know that this is an unwanted distraction when you're suffering. Castelli may have a reason for putting the seam there (perhaps to "shield" it from rear wheel water spray?); however, I'd happily trade this little bit of ultimate water resistance for not having a seam located in perhaps the worst possible location.

Now for what's great about these shorts:
1) Fit - They fit great like all other Castelli shorts I've owned or tried on which means they're sized for a lean, biker's body. So for me the fit is "true to size" while most other brands run large. The thicker yet-still-very-stretchy material makes them harder to put on vs. a summer-weight short, but while riding they feel like a "normal" race-cut bib to me (i.e., compressive/conforming but not overly tight or restricting).
2) Length - These are longer than your typical summer-weight short, which for me meant they come down to the top of my knee caps. I found this length to be great since I will generally be wearing knee warmers under them (i.e., the added length keeps the knee warmers in place better and allows the knee warmers to be pulled further down if needed).
3) The upgraded Kiss Air chamois seems to work nearly as well as the Progetto X2 (which is one of my 2-3 favorite chamois's). The cushion at my sit bones feels a bit less isolating due to the lack of the Progetto X2's gel inserts. However, I'd still consider it to be as good as or even superior to many other brand's top-end chamois's, which makes it a steal at this price point (so much so that my next summer-weight bib purchase will probably be a lower-end Castelli with the Kiss Air chamois).
4) Warmth - Definitely provides the added warmth in 40-50deg. weather that I was seeking vs. my summer-weight bibs (and I generally don't ride in temps lower than that).
5) Water-Resistance - Definitely fends off light rain and road spray. However I chose to wear rain pants over them during periods of heavy rain (for me the possibility of riding with a wet chamois isn't worth it just for the sake of seeing how water resistant this shorts are).
6) Miscellaneous - The Giro3 leg grippers have worked great for me in the past and so far these do too given that they're tighter than on a summer-weight short (i.e., since they are gripping the narrowest part of my thigh just above the knee). Finally I might complain about the bunchy traditional seamed-mesh bib straps but at this price it's hard to expect much more (and I'll generally be wearing them over an undershirt such that this issue is not really noticeable).

In conclusion, other than than the oddly placed rear seam, these shorts do what they claim to do (and do it better than the thermal shorts from Bontrager or P.I.). They are a steal at this price for something with the Castelli name on it. Buy 'em unless you see value in the extra cash needed for the likes of the Assos or Rapha thermal bib shorts.


  • Familiarity: I've put it through the wringer
  • Fit: Runs small
  • Size Bought: XXL

These are the cold-weather cycling equivalent of a good sourdough starter. I wear them in the high 50s, add knee warmers down to the low 40s, and supplement with a pair of thermal tights over the top in the 30s. Anything colder than 30, and I stay inside and drink whiskey.

The water resistance hasn't faded over a dozen+ washes. While Nanoflex won't keep you dry in a deluge or if you jump into a pool, the material does the trick in sprinkly conditions or if the road's damp. I opted for a slightly more accommodating fit with XXL rather than risk a see-through ass panel on the XL. You're welcome.

Great shorts!

  • Familiarity: I've put it through the wringer
  • Fit: Runs small
  • Size Bought: Large

The shorts provide a lot of extra warmth when the weather gets down into the mid 30s. I have used them with legwarmers down to the mid 30s easily . In cooler weather, or use a heavier tight with these and stay very warm. They are pretty snug, but they xdo not ride up When you're wearing them with tights.

What makes these different to the nanoflex 1 shorts?

Best Answer

The only thing I can see just from reading the product description is nanoflex is a Kiss 3 and the nanoflex 2 is a Kiss Air chamois.