Is it necessary to have the tire and rim be separate objects? Any bad effects if they are one object? I am wondering how rFactor decides what polys can be deformed for the tire flex. Perhaps just the sidewall material ?? ( I have split 1 front wheel into rim and tire and left the other as 1 object and have seen no difference in testing so far... )
It might need to be separated for damage, but I don't know if you can even damage the tire or rim. Tire flex only works on materials with the tire shader.