Puncture protection tires are available (quite expensive) which have either an inlay of thick elastic material or a web of strong fibres. Liners can also be placed between the tire and the tube. An alternative to buy one of this products is to cut the bead of old tires and mount them as liners inside of the tires to be protected. Check this site for more information: http://bicycling.about.com/od/bikemaintenance/a/avoiding_flats.htm
All this systems give some amount of protection. However, a piece of glass that is big enough will make his way through any of the above protections. I propose you here a cheap and hopefully effective alternative. Of course this armouring increases rolling resistance and weight. However, these effects cannot be noticed in my 20 inches folding bicycle and I really don't care.Para ver la versión en español seguir este enlace.
- old tires, thinner than the tires to be protected,
- self-retracting tape measure;
- an old brake cable