Below are some instructions I got from Northface. I followed these and used Nikwax, and had only so-so results. I've redone it once. I didn't notice any difference in breathability, but this was not a cycling jacket that I used it on.
One option: Forget about breathability. On a bike you're going to overwhelm that anyway. Just get a non-breathing rain jacket with vents.
I recently got
this jacket, but haven't tried it yet.
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C. My Gore-Tex® jacket by The North Face is leaking. What can I do?
Gore-Tex® garments are made of a nylon outer fabric that has been laminated to a Gore-tex® membrane. This nylon outer fabric is treated at the mill with durable water repellency, called DWR. DWR is a substance like Tectron® or Scotchguard®, only it is much longer lasting. The Gore-Tex® membrane is what keeps raindrops out and allows body vapor to pass through. Once the DWR wears off, water will soak into the nylon layer of the jacket, but Gore-Tex® membrane will keep water from soaking all the way through to your skin.
In order to revive the DWR, the product needs to be thoroughly cleaned with a powder detergent (do not use liquid) in a regular washing machine, in warm water. Put the product through two rinse cycles to ensure there is no detergent residue. Then dry it in a regular clothes dryer, on medium heat. When cleaning your Gore-Tex® jacket, be sure to attach all Velcro® closures and zip all zippers. Finally, the entire outside of the garment should be touched up with a warm iron on the steam setting.
This process should revive the DWR. For even better performance, treat your product with a coating of a DWR spray, such as Tectron® or Revivex®. This maintenance program is only required when water stops beading up on the outside of the garment.
In the event you find this process ineffective, please send your Gore-Tex® product in to us. We would be happy to inspect it for you.
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D. My shell jacket will not stay dry anymore. What can I do about it?
All of The North Face Outerwear shell fabrics are treated with a Durable Water Repellent finish (DWR). This finish helps the shell fabric resist wetting by causing the water to bead-up so it easily falls off before being absorbed into the fabric. Additionally, some of our performance fabrics have a waterproof back finish (such as Gore-Tex® fabrics and HydroSeal®) that prevents penetration of the water through the fabric. As a garment is worn and used over time, accumulation of soils from external sources as well as from your own body can lessen the performance of these finishes.
In order to revive the DWR, the product needs to be thoroughly cleaned with a powder detergent (do not use a liquid detergent) in a regular washing machine in warm water. Put the product through two rinse cycles to ensure that there is no detergent residue, then dry it in a regular clothes dryer on medium heat. When cleaning your Gore-Tex® jacket, attach all Velcro® closures and zip all zippers. Finally, the entire outside of the garment should be touched up with a warm iron on the steam setting.
This process should revive the DWR. For even better performance, treat your product with a coating of a DWR spray such as Tectron®. This maintenance program is only required when water stops beading up on the outer surface of the fabric.