[Grant Bowker]

According to the AEDB Design Record (I don't have my copy with me right now to quote percentages) there were significant differences in diamater between tires that were nominally the same ("same" size and all cross country) but of different manufacturer. Since I haven't seen specific reference to matching brands as a means to match sizes on a truck I doubt they used that as a method to ensure size match, but I have seen reference to measuring tires to ensure they were all of similar size on a vehicle. If they took the time to tell the maintainers to check, they must have found the size differences among "same" tires to have caused some kind of handling/driving problem.