Was early afternoon on a hot july day during wheat harvest in North Central South Dakota. I was Driving a 93' John Deere 9600 with a JD 930 rigid head. We were moving from field to field, and this involved going through a small town of about 500 population. It's one of those towns where the mainstreet with all the businesses is the highway that runs through town, Two lanes and parking lanes. It's a bit tricky going through town with a 30' header, you have about half a car width on either side, so being careful doesn't even have to be mentioned. I was leading the pack, had three more 9600's with 930's on them directly behind me and we were going about 15 MPH through town. Since I was in the combine, i did not hear the Fire whistle go off, a custom harvesters truck had caught fire about 5 miles outside of town. I was in the center of town, about 1_4 of the way into the intersection by the town grocery store, when out of the corner of my eye I saw the fire trucks coming full steam ahead at me to my left, and one was already half way into the intersection. In such close quarters, the only thing I could do was slam in reverse on the Hydro and hit the brakes. Some how, in the midst of the instant chaos, i had hit the right brake first which caused the machine to veer to the right, luckily missing a parked caddilac. When my foot finally connected with both brakes, and the hydro being in reverse, the rear end on the combine came off the ground, way off the ground. I distinctly remember hearing the header slam on the pavement, and then the rear end coming down quickly and bouncing twice. I still to this day do not know why the tires didn't blow out on the rear of the combine, or for that matter, why the axle didn't snap. It scared the daylights out of me. luckily no damage was recieved to anybody or anything, but it had serious potential for bodily harm to the firemen and many, many dollars worth of damage to cars, combine, and firetruck. Shook me up for about 2 hours.