The answer to this question is no. There are no good ways to lock a bike to a bike rack. There are millions of bike stolen around the world attached to bike racks and that is the location crooks go to steal bikes. The only bike that should be attached to a bike rack should cost no more than $50.00 dolars and have about $250.00 dollars in chains and u-locks securing the wheels and frame.

Having said that, I did see a Strida 3 locked outside in New York City the other day. He had a simple U-lock I could have poped off in 10 seconds. You lock outside only bikes that you're not afraid of losing or getting destroyed.

Part of the problem with folders is they are ALL too heavy carrying around all day long. The folding bike concept works well if you can drop the bike in a central location and not have carry it around. It requires thinking before hand what you are going to do because any activity that requires lots of indoor walking is not a place you'll want a folder. You can't really take them shopping at a mall or Museum and even rolling the Strida or CarryMe for longer than 20 minutes becomes too heavy. Do you really want to carry a twenty pound bike while also having to juggle packages on the other hand? As for the museum, you almost certainly do not want to lug a 20 pound bike all afternoon.

There is someone on the forum who said you can lug the CarryMe easier than a Brompton however, that's only for a short while. Even the Carryme would become a beast of burden lugging that bike around the mall for an hour.

I still think the best bike for shopping around a mall or a museum is a plain old beater. If the mall has a bike rack, please don't use it! Learn to hide the bike away from foot traffic and your bike has a better chance of survival!