So would I. Nissan recommends 165/60 R 14 77H, and as the 60 erpresents a % of the width(165); if you fitted wider ones the sidewall ratio would need to be smaller, eg... going from 165/60R14 to 185/55 R14
I done this on a tire comparison site:
Tire Size Comparison
SpecificationSidewall Radius Diameter Circumference Revs/Mile Diffefence
165/60-14 3.9" 10.9" 21.8" 65.8" 925 0.00%
185/55-14 4.0" 11.0" 22.0" 69.2" 916 1.00%
195/55-14 3.8" 10.8" 21.7" 68.1" 930 -0.50%
Hope this helps, lads