Originally Posted by fuzz2050

It's true that polypropylene has a fraction of the breaking strength of nylon, but that really doesn't matter. 1 inch nylon has a breaking strength off ~2200 pounds, comparable polypropylene only 600. Either one should be more than strong enough.

Of course polyester is actually stronger than nylon, and more water resistant than polypropylene.

Originally Posted by Western Flyer

Hmm, how to get my point across? There are 600 pound bs nylon webbings and they are still much stronger than 600 pound bs polypropylene. Polypropylene has very poor UV resistance, which mean it losses its strength rapidly with sun exposure. It has abysmal abrasion resistance so anywhere it is subject to chafe like at buckles or rubbing against the rack it will degrade much faster than nylon. It is not as flexible as most nylon and will fail much faster at any point where it is repeatably creased. I'm not saying not to use polypro webbing. It's cheap, readily available and come in lots of neat colors (which tend to fade quickly). Just don't expect it to last forever.

As an additional note, polyester is not as strong as nylon, at least initially. Because polyester has greater UV resistance over time it will maintain its strength better than nylon.

With all that said, I secure my tent on top of my rack with 3/16" red nylon covered shock cord, cut to length and finished with snap on molded nylon hooks.