would it be ok to change a column type - from "text" to "char" - for an existing site?

my aim is to limit the amount of text entered for "description" - which I use as a "short description" - so the limit for "char" 255 characters would be ok.

database has 4,300 records - would this "truncate" any existing"description" text that is over 255 characters?

would this be ok?
Colin Thompson