So how is a bicycle pack made to be "water-proof", and how is it different from a water resistant design (see Part 1)?
Packs sold as “water-proof” start with a very water resistant or water proof fabric, and then add additional features to keep water out. The first step is the use of sealed seams, where a water proof fabric tape is placed over every seam and heat sealed or “welded” to the rest of the fabric. It will also need similar sealing tape over any pack mounting hardware that comes through the pack fabric. Finally, the pack must also have have a waterproof closure, either by using water-proof zippers, or a roll-up closure.
Some of the bicycle packs made in this waterproof design approach the protection offered by a canoe/kayak “dry-bag”, that are designed to protect gear that is at risk of actually be immersed in water. A road touring cyclist may not need this level of protection, but for off-road mountain bike touring, fording a stream and needing a dry-bag pack is real possibility.
A touring cyclist can make the decision on bag to choose based the climate and and packing style. If you use stuff sacks and zip-loc bags to organize all your gear, in effect double bagging everything, a water resistant pack and rain cover is likely to be adequate for all but the most extreme wet weather locales. And if you tour with a true water-proof bag, you must still make provisions to keep damp and dry items seperately bagged.
For the commuter, a water proof bag with a roll-top closure offers an easy way to keep clothing and office gear dry, up to and including a laptop, without the need for double bagging contents or stopping to pull out a rain cover. However, keep in mind that a waterproof bag keeps moisture in; and a damp towel sealed in a water-proof pack for the ride home can damage your office papers and electronics just as much as a rain shower.
So the best descision is base on your type of travel, and you like to organize. In part 3, I will talk about the difference on bag openings, and how to choose what is right for you.
A roll-up closure is the most most water-proof.
Find a full selection of bicycle packs from Arkel, Bontrager and KoKi bicycle packs at all three Bicycle Garage Indy locations: Bicycle Garage Indy North (Indianapolis, Dean Rd at 82nd St.), South (just west of I-65 on County Line Rd, Greenwood), and the new BGI Downtown, in the Indy Bike Hub YMCA at City Market.