Patio End Tables I Want My Chairs To Slide Easier?

I want my chairs to slide easier? - patio end tables

I have thick aluminum chairs around a table on my terrace, see http://www.norths.co.za/cat6.php?catID=7
My patio is made of unglazed floor tiles and squares are difficult to sit and sit once the film table. The ends of the legs are approximately + - 18 mm (3 / 4 inches).
I tried not to feel - well to bear - in a few days.
I have tried plastic cover - a move a little better - but still difficult.
What can I do to get the chairs from sliding too easily.