I just converted my Orbea Alma to a single speed. I went for it without using a tensioner and am using a half-link to get the chain to the right tension. After trying 32X16, 32X18 I could not get the tension right but with a 32X17 the chain fit pretty well. My only concern is the chain is really tight (cranks don't move too freely) is this a big problem? will it be ok once the chain stretches out a little? I might go try 32X19 to get a better tension but that is a little too easy of a gear. Any help would be appreciated.