If a person does not wear tzitzis on Shabbos (this was the opinion and custom of the Brisker Rav zt”l and his talmidim), and he announced to other people that he follows this opinion, is it necessary to do hataras nedarim if he wishes to start wearing them again (such as if a rav convinced them that it is wrong to take on such a stringency that is not in accordance with traditional halacha, and that his loss is bigger than his gain)?
Since general practice is to wear tzizis on Shabbos and very few people do not wear them on Shabbos he does not have to do hataras nedarim. Also he can rely on the formal decleration he said on Erev Rosh Hashonah to annul all future vows and oaths.. Nevertheless maybe it is praiseworthy to do hataras nedarim.
Gemorah Nedorim 23b, Run Nedorim 75b, Ramo Y:D 211:1, Run Ritvah Nedorim 8a, Sulmas Chaim 38, Minchas Shlomo 1:91-20.