I have now 16X8s with 235/55/16s.
Im thinking about 275/40/17s on a 9.5 rim.
I looked up the height for them,but how do they really look and fill the wheel well without lowering springs?

 

Since the 275/40-17 is about 1/2" smaller in diameter than the 235/55-16, you are going to increase the gap between the tire and the fender by 1/4". It will look just like the 4th Gens that came with the 245/50-16 Z-rated tires, as far as the gap.

 

I was also thinking about a 255/50/16,looks to be about 1/2 taller than the 235s?

 

Calculating the diameter from the section width and aspect ratio, a 255/50-16 is about 1/8" smaller in diameter than the 235/55-16.

235/55-16 = 26.18"
255/50-16 = 26.04"
285/40-17 = 25.98"

245/50-16 = 25.65"
275/40-17 = 25.66"
315/35-17 = 25.68"

All that is theoretical. A specific brand or model of a tire may vary by a tenth or two tenths from that value.