Hello; I usually use 250 and give it at lweast 15 minutes before I attempt to remove the bearing. I haven't had one beat me yet. I do find that the more expensive bearings that Boca offer do make a difference. I have a Saito 50 I have used for 6 years since putting the upgrade Boca bearings in it, with no problems whatever: It's not the kind of job I would want to do every year.