I found a great deal on 4 205/50/15 tires I was wondering if the size will be ok for my S70,I currently have the original size on it,195/60/15.

 

The lower profile(50) will result in 40 more revolutions per mile. Results:Higher engine revs and your speedometer will be off.

Check this site for a better match.
www.1010tires.com/TireSizeCalculator.asp

 

Agree on needing to find a better match. The only reason you want to go down in profile is if you go up in wheel size, say to a 16" or 17" wheel.

 

Most people want to put a tire on that's a little bigger than factory not smaller, and 205 50 is smaller than 195 60 as far as outside diameter of the tire. Here is the meaning of the numbers:

195 or 205 is the width of the tire in MM
50 or 60 is the percentage of the width for the tire height
15 is the size of the wheel

Hope this helps.

 

To avoid significant speedometer error, you want to try to closely match the stock tires' circumference (or diameter, as they are proportional). Here isa very handyonline site with a calculator to compare your stock wheels and tires to any other set you are contemplating changing to, and giving the speedometer error as a function of speed.
http://www.web-cars.com/math/tiresize.html

If you play with it, you will see that 205/55-15 is a much closer match to 195/60-15...