I had 185/60 x 14 tyres on my coupe on std Lancia rims. The overall diameter of the tyres is less than the 175/70 x 14 originals, so your speedo will read slightly faster than you are actually going, but not massively so. I have used 185/60 x 14, 195/60 x 14 (closer to std diameter), 195/55 x 15 (very close to std diameter and same as 185/65 x14 as used on VX) and now 205/50 x 15!
I didn't find the steering excessively heavy with any of these, or maybe I have Popeye arms!! (The car does not have power steering) I used to drive a MK2 RS2000 escort with quick rack etc and was much heavier to steer!
At 70mph your speedo will read 67.4 mph
Here are some tyre size comparisons:
size diameter circumference Difference
195/60 R14 590 mm 1854 mm -1.83 %
205/60 R14 602 mm 1891 mm 0.17 %
185/65 R14 596 mm 1872 mm -0.75 %
195/65 R14 609 mm 1913 mm 1.42 %
175/70 R14 601 mm 1888 mm 0 %
185/70 R14 615 mm 1932 mm 2.33 %
205/50 R15 586 mm 1841 mm -2.43 %
195/55 R15 596 mm 1872 mm -0.85 %
205/55 R15 607 mm 1907 mm 0.98 %
175/60 R15 591 mm 1857 mm -1.6 %
185/60 R15 603 mm 1894 mm 0.4 %
195/60 R15 615 mm 1932 mm 2.4 %
There are several tyre calculators on the net, here is one:
http://www.alloywheels.com/tyrecalc.aspRegards Ian