I always try to stick to manufacturer recommendation. For Vitz it is 165/70. I am still running original ones that came with my Vitz. However, I have to change them in a month or two but 2 different tire shops nearby my place have told me that 165/70 new are hard to find so I shall try finding 175/70. To me, 185 profile tires look too wide on original Vitz rims so I won't go for them unless I have no other option left.
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