by John Brown, HaveFunBiking.com
In the rains of the fall and early spring, staying dry is the most important and difficult part of riding. The best way to stay dry is to wear waterproof clothing. While most synthetic fabrics still insulate when wet, being wet diminishes their ability to keep you warm. A jacket and pants are a great way to start, but socks and gloves make the outfit complete. In their most basic form, a lot of materials are waterproof, but as soon as they are perforated with stitching, zipped closed with generic zippers, and left to be loose at all the cuffs, their waterproofing goes out the window. Before you go out and buy anything labeled “waterproof,” understand that all waterproofing is not the same.
Waterproof Clothing and Gear To Stay Dry
To keep water out, look for waterproof clothes that have sealed or welded seams (see image). Also, look for waterproof zippers (pictured) or large flaps that prevent water from driving through the zipper. Make sure all the cuffs are adjustable enough to be snugged tight against your skin.
Examples of cycling clothes with taped seams (Left), welded seams (Center), and a waterproof zipper (Right)
A waterproof garment is measured in mm of fluid. For example, a fabric that were 5,000 mm waterproof is tested as follows. Fabric is placed over the end of a long tube. Following that, the tube is filled with 5,000 mm of water and the fabric needs to support the pressure without leaking. For example, take a look at the table below for an quick reference.
| Rating | Resistance | Weather Conditions |
| 0 mm – 1,500 mm | Water resistant/snowproof | Dry conditions or very light rain |
| 1,500 mm – 5,000 mm | Waterproof | Light to average rain |
| 5,000 mm – 10,000 mm | Very Waterproof | Moderate to heavy rain |
| 10,000 mm- 20,000 mm | Highly Waterproof | Heavy rain |
Let Sweat Out
In addition to measuring waterproofness, waterproof materials are also measured for their ability to breath water vapor out. Breathable means that water from the outside cannot penetrate the fabric. However, water vapor (sweat) being produced by your body can escape through the fabric. Breathable fabrics work because water vapor is smaller than water droplets. In order to breath, the material will be perforated with holes small enough to stop water droplets from getting in, but large enough to allow water vapor to escape.
Breathability is important because, as far as insulation is concerned, it’s just as bad to get soaked with sweat as with rain. Therefore, using a breathable material in tandem with base layers designed to pull moisture off your skin is a sure fire way to stay dry and warm.
Breathability is expressed in terms of how many grams (g) of water vapor can pass through a square meter (m2) of the fabric from the inside to the outside in a 24 hour period. To that effect, the larger the number, the more breathable the fabric. For example, if a coat were 5,000 gsm breathable, 5,000 grams of water would be able to pass through a square meter of the fabric in 24 hours.
When Waterproof is Not Important
As the temperature rises, waterproofing becomes less and less important. It’s less important because at a certain temperature, waterproof materials cannot breathe enough to keep you dry. Therefore, if it rains hard enough, and it’s warm enough, you’re going to get wet.
In the spring and fall, be sure to have your waterproof gear ready. The cold temps and wet conditions coupled with the accelerated rate air is pulled away from your body while you ride can be very dangerous if you aren’t prepared. Being dry is the #1 way to maintain your comfort and safety while riding in inclement conditions.