Having ridden a folder around in the past, I can say that they're more
expensive than a standard bike, and when folded, they're heavier than
you'd like and have sharp bits poking out. Their main advantage is
that you can often taken them on public transport and you can store
them in small spaces - under a table or in the boot of a car, for
example. Their main disadvantage is that they aren't as effective as a
full-size bike when actually riding.

If that doesn't bother you, here's what you should look for in a
folding bike, in no particular order:

0. Ease of folding. It should take 15 seconds or less to fold the
bike, with practice, and when unfolding the bike should be easy to
reset to your riding setup. If it takes much longer than this,
there'll be little point to having a folder in the first place. Also,
cables, levers and so on should not snag on anything during a fold or
unfold.

1. Size when folded. None are as small as you want. Basically, when
folded it's going to be somewhat bigger than the wheel size, no matter
what. The Brompton is the smallest, but it isn't all that small if
you're carrying it.

2. Weight. This seems to bottom out at around 15kg for most of what's
on offer. Below 15kg there's much less choice, and every kg saved
costs a surprisingly large amount of money.

3. Wheel size. Smaller wheels are, well, smaller... but less stable on
the road. I wouldn't go below 20 inch wheels, myself, but I suppose
that's down to individual preference.

4. Strength of the hinges. You want strong hinges and catches that
close tight, don't creak, and can be easily tightened as they loosen
up over time. The weakest link is usually the steering stem hinge. The
stems tend to be quite long on folders, and so they cop a lot of
bending force. (Which is why you're not supposed to stand on the
pedals to push up hills.)

5. Ridability. Most folders are, at the very least, short. They also
tend to have very little trail in their steering. Trail makes a bike
self-steering to a large extent; small or negative trail has the
opposite effect and makes steering very twitchy. Consequently most
folders require more attention when riding.

If I had to recommend anything in the middling price range, it'd be a
Dahon or a Yeah. They're made in the same factory and use the same
components, but Yeah tend to be a bit cheaper. They're both fairly
common, reasonably priced for folders, and well-made. They also hold
their resale value fairly well if they're looked after, which is
useful if you decide that a folder isn't for you.


-- Phil