tire size

[withm]

If I had 3 nail punctures in the same tire, I'd be inclined to replace the tire regardless of the amount of tread left. Going to a narrower tire is probably not the best idea - a 20mm is really for racing and will not give you any maneuverabilty if you encounter sand or gravel on your commute, or support increased loads assuming you are carrying clothes, computer, lunch, etc. to work.

If anything, I'd suggest you switch to 700Cx25 and keep them inflated to the max. This will help to avoid pinch flats and increase the probability that nails, glass, or other debris will bounce off the tire rather than penetrate it.

[pinkbikes]

I recently got a new bike and had four flats in my first five rides. And I nearly never get flats, so I was NOT happy!

But perhaps you need to look at the type of tyre you are using? The tyre that came as original equipment on my bike was as soft as butter and was ideal as a race tyre but no good at all for everyday use.

I replaced it with a tyre of the same size (700x25) but in a more robust structure. I personally have a liking for kevlar bands in a tyre that is going to be used for everyday. No flats since.

Perhaps if you don't like the behaviour of the tyre you may need to look at an alternate instead of replacing it with the same (and not a narrower one) to get different behaviour.

Oh - and sometimes it really is bad luck (or a big nail) and you would get a flat no matter what tyre you had!