Folding Bike tires going flat I have a Miele Compatto folding bike and the tire and rim size are currently 20" x 1.50. I find that the tubes don't last very long (at most 15 km) I get a lot of flats. Should I increase the tire width to a 1.75 width or possibly buy better more expensive tubes/tires?
Next time you get a flat, take the tube out but keep track of which is side is left and which is right relative to the bike (and mark it).  Inflate the tube, outside of the tire, to about 1.5 or 2x its normal diameter, then immerse it in a basin of water and find the leak.  

A leak on the inner diameter indicates a missing/defective rim strip, or a spoke that has been dislodged and is poking the tube.  A leak around the valve is likely due to under-inflation or lack of care mounting the tire.  Two leaks closely spaced together near one side of the tube is "snakebite" and indicates hitting curbs, etc, while the tire is insufficiently inflated.  And of course, a leak from the valve itself is due to a defective valve or one where the core is not tightly screwed in.

You may also find leaks where you damaged the tube during installation -- especially likely if you used screwdrivers to mount the tire.

After you find the leak (and the cause is not obvious), place the tube, with the hole marked, alongside the tire and find the corresponding point in the tire.  Check from the inside (both look and feel it with your hand) for any piece of wire or glass or whatever that might be stuck in the tire tread and poking through.