A 255 tyre will fit an 8.5 rim with no problem. Yes the height of the tire would increase but i am from Mexico streets here are pretty shitty, i need a higher percentage profile, i already got two flats with the stock tire and my RS only has 3000 kms and I dont want to keep getting flats, its only 2.1% higher than the stock tyre i am just concerned about width more than height.
but thanks anyway