The success of Castelli's insulated and extended length Omloop Thermal Bib Short isn't surprising, not is the fact that Castelli made the move to add their Nano Light water repellent treatment to the Omloop concept. Cool and dry is different than cool and wet, so the option is welcome. The added water protection is welcome, especially for those in wetter regions that train for road or cyclocross, but all also commuters and enthusiasts who embrace the conditions as part of the positive experience of cycling. The Castelli Nano Flex Pro Omloop Thermal Bib Short adds a very versatile piece of gear to any cycling wardrobe.

If you start with a concept that riding in the 54-65°F temperature range in shorts or bib shorts is not only feasible, but enjoyable and preferable to knickers, or lighter weight shorts with knee warmers, you have the essence of the Omloop series. By adding a true knee length to the short section, and insulation that not only covers the top of the knee and thighs, but also the lower core muscles, hamstrings and glutes, you have a higher level of consistent insulation and protection without restriction down and over the knee. By adding water protection, you block off penetrating cold from wetness that standard Thermofleece isn'd designed to defend against.

Castelli developed Nano Flex as a system. The base fabric is Thermoflex fleece, with it's brushed, soft fleece inner finish. That fleece adds loft, trapping heat, and releasing moisture off the skin as a byproduct of movement. The woven outer finish blocks a little air, but generally allows the excess and heat and moisture to escape. By adding a coating of millions of nanofilaments to the exterior, water is blocked from penetration, while moisture is still allowed to escape. More heat is held in, and less incoming air means the fabric can be lighter yet still increase thermal properties. That is the premise of Nano Light, which reduces the bulk of the fleece so movement is less restrictive and the wearer doesn't overheat. Rain runs off, but even if the piece is overwhelmed by water and mud, you still get the thermal properties you require.

Using Nano Light instead of the heavier Nano Flex works great for this piece. You get very consistent tension and stretch, with limited panels and seams (which limits entry points for water). The material is conducive to very clean finishing, with the raw-cut edge of the leg openings around the knee the best example. In order to be comfortable and add protection, the front of the leg opening needs to be longer, lay flat, and provide consistent feel. The rear has be cut shorter, to prevent discomfort and rubbing behind this active, constantly changing zone throughout the pedal stroke. The raw-edge finish is smooth, durable, and easily shaped for this purpose. You feel great support from the moderately compressive material throughout the short section, which holds in place the pro-level Progetto X2 Air seat pad. This flexible, breathable pad stays in contact with the stress zones, but moves with the body, limiting friction. The sculpted padding is of variable density, with excellent protection without bulk.

The Nano Light carries up and over the hip bones and lower back, but fades into a full back, short front mesh material through the bib straps. The edges are finished with soft material which increases overall comfort and stability, while the mesh quickly and efficiently removes moisture and excess heat to the next layer. Castelli generally promotes this concept in all but their most heavily insulated bibs, as dressing the upper body with proper layers offers better temperature and moisture management, especially in changing conditions.

The Nano Flex Pro Omloop Thermal Bib Short is truly a performance piece designed and built for the needs of pro cyclists, yet is equally embraced by those who love to ride outside in any and all conditions. By adding rain protection via nanofilament technology, the designers warmed the hearts of cyclists of the Pacific Northwest, NorCal, and New England, but really, unless you live in a desert, temperate North America has plenty of seasonal rain and cool temperatures. If you are a cyclist who has been waiting for a long bib short with light insulation and rain protection, Castelli delivers. We advise sizing up in this piece if you fall into the upper spectrum of each size range.