cr125matt said:
unless your riding behing people then you will need a chest protector
Let me rephrase that: If you are riding behind someone then you really need a chest protector.
As a beginner you are not likely to be leading a trail ride, so that means that you should have one.
A chest protector provides two forms of protection:
1) When you are following close behind another bike and they gas it on soft terrain the bike's tires will kick up dirt/rocks and throw it at you. This can hurt! The chest protector at least shields the bulk of your torso. Note that the most likely place to get "roosted" is at the track, especially when the guys on the 450s pass you in the corners.
2) A track is generally soft dirt and other than the roost from other bikes a chest protector isn't that important. On the trail, however, a fall can send you tumbling across uneven terrain / rocks. The most common fall is laying the bike down in a turn, which is generally not too bad. Failing to climb a hill, however, will often end with you and the bike tumbling back down the hill. In this scenario you are falling 5 or more feet onto your back and if there is a rock there you can be in for some serious pain. Then, sort of like the road runner cartoons, the bike tends to fall on top of you. The chest protector comes in really handy.
The worst falls are when you go over the handlebars. In the uphill fall you at least come to a stop for an instant before the fall. In the over the handlebar scenario you hit the ground going whatever speed you were going when you got into trouble. If this happened to be going downhill the fall distance can be quite long. The more pads, the better.
Rod