I was going to change the rear tire on the C70 last night, when I noticed that it was in pretty good shape. The front was all cracked and worn, so I had replaced it, and had thought the rear would be the same. But, there is no cracking, and plenty of tread left. But, I noticed that it is the wrong size. When the previous owner changed the tire, he used the same size as the front, which is 2.25/70. The correct size is 2.50/70. Although it will run fine with this smaller tire, the top speed will be reduced slightly, while rate of acceleration is increased. I decided to just keep the smaller tire on the back for now, and when I have more room in the new house/garage I will replace it.