I have noticed that sometimes the knots (not the strings) on a the tzitzit from a Tallit Katan or a Tallit Gadol either come or become tangled. Is it permissible to untie and then retie the tzitzit? I don't see a reason why it wouldn't be, but I wanted to ask.
As far as I know(I am not a Rav): there is no problem, Moreover - if the first knot (that is near the talit) became loose the Tzizit might not be Kosher. If you re-tie the first knot you should cocentrate "L'eshem Mitzvat Tzizit" since it is the "Mederoita"