Tire combination question
27.5/2.54 = 10.82677 section width * 0.40 (sidewall heigght as % of section width) = 4.3307 sidewall height * 2 = 17 (wheel diameter in inches) = 25.6614 overal height.
Your choice of tire size with an 18 inch wheel would be 26.976 tall. Your overall gearing will be reduced and the speedometer will be incorrect.
A 285/35/18 would be much closer to stock dimensions.

