I'd it possible to purchase 16" studded tires? I have an old Dahon I use as a winter bike, and I'd like to replace the tires with proper snow tires if this is possible. If not, has anyone here successfully made studded tires from smaller-wheeled knobbies?
The best thing to do is make your own studded tires from the old tires you have. You can buy roofing nails for very cheap, and put lots of studs on the tire (most commercially available studded tires don't have that many studs).
Push the nails through from the inside of the tire, wherever you want them. It's a good idea to put some on the rolling surface, and some on the sides for cornering. Once you have placed all your nails, put a layer (or two) of duct tape over the heads of the nails to protect the tube. You'll probably need to trim the nails down to the desired length with metal clippers. That's all there is to it!
EDIT: I have had luck with nails in the past, but on looking around at studded tire designs online, I realize that screws may in fact be a better option, as they will better resist backing out, and would be easier to replace. Scroll down on this page for DIY instructions.
At the time the question was asked, there were no 16" studded bike tyres. Now, however, there are: http://www.schwalbe.com/en/pressereader/spikes-for-birdy-and-brompton.html
But unfortunately there are two different 16" rim sizes, and the new Schwalbes are 349mm (as used by Brompton), and 16" Dahon is 305mm. It might be possible to fit a Brompton sized wheel in some 16" Dahons, but I wouldn't bet on it.
(Since the title asks about "small wheels" and readers with other size small wheels might find it in a search: 20" studded tyres, as used by different Dahons, have been available for a while, e.g. Marathon Winter . It's possible to fit a 20" wheel in a Birdy, but only with a skinny tyre, so the new 18" makes a studded Birdy possible.)
I have two links for you:
First you can by Schwalbe Ice Spiker tires at MEC in Canada (The reviews are quite favorable).
Here is a list of different studded tires on the market.
The best option is to make your own tires as previously stated.
Since you don't like the idea of using nails or screws as studs, (which I agree with), try using pop rivets instead.
It is more time consuming, but they work better, are more durable, and will stay in place better than a nail or screw.
Use a small, sharp drill, usually 1/8", and drill through the knobs of the tire from the inside of the casing.
Select a pop rivet which will just protrude from the knob of the tire. Stainless steel is most durable. Place 2-4 rivets approximately every 4 inches around the tire. (On a 16 inch tire, 2 inches might be better.)
Fill the divot created by the compression of the rivet on the inside of the tire with silicon. That prevents the back of the rivet from popping the tube when installed.
I hope this helps.