Imola- in the future may I suggest the use of a touring type compound for the rear tire, with a "sporty" tire up front. In general, you will wear out a rear quicker than you would a front tire, so using a softer tire up front should make them wear out at about the same time. This also gives you the benefit of having a grippy front tire that can take really hard braking without locking up. The reasons for locking up your front tire have already been stated (grabbing too much brake, too fast), but a better tire will be able to take more pressure faster without locking up. A general rule with tires is that you want your front as sticky, if not more so than your rear tire. When I was into high-mileage street riding, I used a BT010 front, BT020 rear and it was AWERSOME. The BT020 and D220 are very similar in life and traction, BTW.

Keep in mind for the future that if your front tire chirps from locking it up, ease off the brake momentarily without letting off of it completely. If you don't ease up, it will slide and you will be feeling pavement in a hurry. You should be able to lock the front in a stoppie and keep it up if you know what you're doing. Ask Bob about the St Patty's Day parade this year, I was having a bitch of a time keeping the front from locking up on cold pavement!