Anyone own a foldable bike? How is it?

Seeing more and more folding bikes in the city, and wondering if anyone has pros/cons about the bikes. this would not replace any of my bikes, but it may be fun to take into the city every once in a while.

I am working on designing a series of folding bikes for one of my customers. For the sake of this answer I will assume you are from the US. If you are in the UK my answer would be different.

Just like any bike, there are GOOD folding bikes and BAD ones. Good ones are the higher end models from Dahon, Bike Friday, or Brompton, while BAD ones are from Fuji and Kent. Models from Giant aren't too bad. Some general features to look for are:

1) Little or no frame flex when you ride. Yes, it is VERY important that you test these bikes as some feel like a wet noodle when you ride;
2) Internally geared hubs rather than derailleur system, preferably Sturmey Archer or SRAM;
3) All alloy components (though not necessarily the frame);
4) Ease in folding/unfolding.. again, try it yourself;
5) Ability to lock on closed position (or it might open as you walk along with it);
6) WEIGHT- look for bikes under 25 pounds- a sack of potatoes- since these things get heavy pretty quick.

The neat thing about these bikes other than their foldability is that they generally sport small wheels which provide much faster acceleration and handling while a bad thing is that they generally sport smaller wheels which provide a much rougher ride.

A decent folder will cost you between $400 and $600, with the yucky stuff starting around $150 and the premium (we are talking better than most road bikes here) get to about $4000.

It's very convenient in small places where you lack storage space.

My buddy had a KHS which I didn't think was too bad. I've ridden Montagues too... They're okay.
http://www.transalt.org/features/folding...
Check out this link. If I got a folder, I'd probably get a Friday or Moulton. There are some great new full size bikes that use couplers. You could have a custom built:
www.taylorbicycles.com

I have a Dowtube folding bike purchased off of eBay from the company for $240. It's probably a bit heavier than some of the upper end makes and models like a Dahon or Birdy but weight savings is not the reason to get one. I liked this model because it was cheap and uses a lot of standard road/mountain bike components. Being cheap saves money for upgrades and customizations, but being cheap also means that the components are not as smooth and don't provide the same response and action as something like a basic Shimano Deore set would. I am slowly going through the back, from front to back and replacing the brake levers, wheels, etc with something nicer. The front fork takes a disc brake so I added one of those and the front wheel is now a nice Mavic BMX X. The cheap brake levers and goofy SRAM twist shift is gone and replaced with integrated Deore brake/shift levers. Next on the list is a decent single speed crankset and a better bottom bracket. I like wrenching so I don't mind these projects at all.

Otherwise, the bike rides just fine. It shifts as it should. Stops as you would expect it. Perhaps a Birdy would feel better out of the box but I don't know. They are really expensive and not worth it to me since I am not a connoisseur of folding bikes.

The Downtube folds up fairly nicely and makes it easy to travel. I don't fold it often so I can't do it in the 15-30 seconds that the ads claim but it does come down to the size you see on the websites.

Just be careful of the geometry. I could not get the seat forward enough so that my knee was over the pedal axle when the pedals are in the 9 and 3 o'clock positions. The first upgrade I had to do was replacing the stock seat post with a Thomson negative setback post and now all is well.

It's definitely a fun bike to ride. You will feel like you are riding a Toon Town bike. People will stare. Enjoy it! :-)