I had a dispatcher call me in the office once when my night was almost complete.. He told me they had an overflow and he had to have me take a single to a meet point about 2 hours away from our hub. He threw me some keys and told me to take this tractor. You are already late. Don't bother to pretrip, just go. I was new to feeders. I got to the meet point and there were several drivers from my building already waiting on some drivers from Mesquite and Dallas. I drop my load and go over to hang out with the other drivers to wait. One of the guys asked me if they had fixed the flat on that tractor I was in. I checked it and one of the inside duals was flat. The driver told me he had caught it and refused to drive it. I asked him who he had talked to about it and he told me the same guy who had dispatched me. So he had dispatched me with a tractor who he knew had a flat, and told me not to pretrip it. I was pist, and raised hell when I came back in. I know it was my fault for not pretripping. I learned a big lesson. I never did that again. Bottom line is, management will tell you most anything to get their arse covered, to hell with your safety, or the safety of the general public.