The 4894 I bought for a scraper tractor had poor tires. We have put several hours on it pulling a scraper and that is the primary purpose now. Someday it may do some tillage, but that is in the future. On other tractors I have always replaced all tires at the same time, but we are using it in rough ground with some rocks and sticks. Would like to get as much out of each tire as possible, because you never know when you will cut a tire. Radials will be $1500 each, bias $1000. If I put individual bias tires on as needed, will I damage the power train? The existing tires are radials and are about 40%.