Article by Siroko Tech: Siroko SRX Cycling Vest with Thermal Insulation

Article by Siroko Tech: Siroko SRX Cycling Vest with Thermal Insulation

Siroko Tech (Spain) - When it’s time for cyclists to bundle up, there are many options, but the most versatile garment, easy to put on, take off and tuck in a pocket, is a cycling vest with extra thermal protection such as the Siroko SRX Ultra Warm. Thanks to this accessory, you can keep using your summer or transitional season clothing even in colder periods of the year. More importantly, you get the performance and adaptability difficult to achieve with other garments thanks to the properties of the fabric and the specific features of the vest. At the end of the post, we are going to give you some tips on how to make the most of all these possibilities of our vest, but first, let’s take a closer look at its features:


This cycling vest, apart from the fabric itself, also features the insulation. Both complement each other and, as a result, we get a garment that protects us from rain, wind and cold, maintains thermal comfort and good level of breathability to help us stay dry and comfortable.

Let’s take a closer look at its double-layer fabric with ITTTAI® Waterproof Technology. The outer layer has a water-repellent coating (DWR) and it is made of an elastic fabric blend (85% polyamide, 15% elastane). Underneath the outer layer, there is a membrane (100% polyurethane) with 10,000 mm water column and up to 6,000 g/m²/day breathability (more info here). This membrane provides continuous micro-ventilation to release the water vapor generated during intense activities such as cycling. The vast majority of polyurethane membranes only start to perspire when they are wet. In contrast, the structure of this specific membrane contains billions of pores and does not need to get wet to start breathing – it does so instantly, keeping you dry and providing more comfort. Other key features of this fabric that are particularly relevant for cycling include its light weight and abrasion resistance.

The PrimaLoft® Gold Insulation Eco is made from 100% recycled materials.

This synthetic insulation offers enormous advantages for cycling and other aerobic sports:

  • It uses ultra-fine fibers that create micro air pockets that retain body heat. 
  • Very good insulation-to-weight ratio resulting in lightweight and compact garments.
  • Maintains thermal comfort even in extremely wet weather conditions.
  • Hydrophobic (water-repellent) properties. In order to get soaked, it must be subjected to a heavy downpour or many hours of constant rain.
  • Excellent breathability thanks to ultra-fine fibers.
  • Lightweight and compact, every cyclist’s dream combination.
  • Softness level similar to down jackets.
  • It can be easily washed, following the manufacturer’s instructions on the label (cold wash, do not dry clean, do not soak. Do not use bleach, fabric softener, tumble drier or iron).


The design and construction of the vest also play a key role in making sure that the insulation does its job properly and that body heat does not escape. Therefore, the flat inner seams, high collar, elastic bands at the bottom hem and around the armholes, plus the snug but not excessively tight fit are crucial to make sure this SRX Ultra Warm vest provides proper heat retention and protection against wind and water. It features a drop-tail, meaning that the rear panel is slightly longer than the front panel, adapting to the rider’s position on the bike and protecting the buttocks and lower back from splashing water.


Another aspect to consider in order not to lose the insulating properties of the vest is choosing the right size. Take your body measurements bearing in mind what other garments you are going to wear under the vest. The situation changes depending if we are going to use it over a base layer and a summer long sleeve jersey or if it is going to go over a thermal base layer and a winter jacket. Taking such measurements may take a little longer, but it is worth it because if the vest is too tight, the air pockets of the insulation compress and do not retain body heat well.


The two-way semi-automatic SBS lock means that it does not slide freely unless the pull tab is lifted to a certain point. It allows you to open the zipper as far as you want, and when you lower the pull tab, the zipper stays in place plus it can be unzipped not only at the top, but also at the bottom. Perfect for when we face a climb, we do not need extra protection from the wind and cold, but we are looking for more ventilation. Once we get to the top, all we need to do is close the zipper to face the descent.

The zipper has a garage at the top to prevent chafing at the neck plus a fabric underlay that helps avoid snagging and also blocks the air from entering and stops the zipper from jamming when it is being pulled up or down.

There are two rear pockets on both sides on the back featuring invisible zippers and elastic pull tabs. They’re perfect to keep your phone, keys or wallet as well as energy bars and gels. If the pockets are empty, they can also be used for extra ventilation, but it is better to simply open the front zipper a little lower.


There is a reflective Siroko logo on the left side of the chest plus the SRX logo and the triple crossed line running from top to bottom down the middle of the back. 


The temperature range for wearing this vest is between 5 and 15 °C, so we can use it mainly in transitional seasons and during relatively mild winters. Now, let’s remember that a vest is not a jacket or a winter jersey. It is an accessory, a complement that reinforces and enhances the performance of the other garments. Such a vest, worn over a base layer plus a summer jersey and some arm warmers, will not be enough to keep you warm at 5°C. However, that same combination worn when it’s between 10 and 15 °C outside might be comfortable and warm. 

It all depends on the person, but with an outside temperature of 5 °C, it is recommended to combine this vest with a short or long sleeve base layer and an M4 long sleeve jersey, or a merino base layer and a long sleeve jersey. Wearing this vest at 5°C on top of a short sleeve jersey and a short sleeve merino base layer is an option only if you have a tendency to get very hot on a bike or you are going on a short and intense training session.

The great thing about this SRX Ultra Warm vest, besides the fact that it offers much more thermal comfort and protection than a basic cycling vest, is that it is very light and compact. Not as light as our V1s, but it does fit easily into your rear pockets or, if you’re carrying a lot of things, can be tucked under your jersey. So you can wear it any time of the year whenever you feel you might need it. If summer mornings or afternoons/evenings and transitional seasons are cold in your area, if you have a tendency to get cold or if you are going on a route with long descents in high mountains, take it with you, just in case. As we always say: better safe than sorry. Even more so when talking about a garment that we can take off, put on and store so easily.

For more information about this article from Siroko click here.

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