Can you use 205 70 r17 instead of 205 50 r17?

Can you? Yes. Should you? Absolutely not. You will have a tire that is a whopping 11.39% or (10.32 Inches) larger in diameter. Your speedometer will be 12.84% or (7 mph) too slow at 60 mph. Want to go with a 70 series tire then you will have to go with a 155/70-17 which would look horrible on your car if you can even find that size. Stick with the OEM size.