I was chasing after a friend on my track around the house (4 acres prime desert, 0.3 mile loop). I went into a turn looking to use both brakes and had zero back brake. I was distracted by this and looked for it twice. Should've just adjusted quicker with more front brake and kept to my line. Instead I went a little wide and came to a stop with my nose in a mesquite bush. No harm done. The problem arose because my plastic disk guard had warped a little and was rubbing against the disk. Couldn't hear it rubbing. It melted and got into the caliper resulting in zero rear brake. The plastic guard had worn out from the AZ climate and was very brittle. That is why it warped. I took it off (fell apart in my hand actually), sprayed brake cleaner on the disk and caliper, check for engagement and rode, burning off any residue. So if anyone has a used plastic rear disk guard they don't want I will pay for shipping.