The OEM size is 145/70/r12 many people shift to 155/70r12 But thats the apropriate size for Alto, Altos OEM tire size is 145/80/r12
Coures tire size should be
215 45/12, diameter diff: -1.87% , speedometer will read faster than actual.
325 30/12, diameter diff: -1.58% , speedometer will read faster than actual.
195 50/12, diameter diff: -1.58% , speedometer will read faster than actual.
245 40/12, diameter diff: -1.38% , speedometer will read faster than actual.
165 60/12, diameter diff: -0.98% , speedometer will read faster than actual.
285 35/12, diameter diff: -0.69% , speedometer will read faster than actual.
335 30/12, diameter diff: -0.39% , speedometer will read faster than actual.
155 65/12, diameter diff: -0.30% , speedometer will read faster than actual.
225 45/12, diameter diff: -0.10% , speedometer will read faster than actual.
OEM TIRE SIZE 145 70/12
185 55/12, diameter diff: +0.10% , speedometer will read slower than actual.
255 40/12, diameter diff: +0.20% , speedometer will read slower than actual.
205 50/12, diameter diff: +0.39% , speedometer will read slower than actual.
295 35/12, diameter diff: +0.69% , speedometer will read slower than actual.
175 60/12, diameter diff: +1.38% , speedometer will read slower than actual.
235 45/12, diameter diff: +1.67% , speedometer will read slower than actual.
265 40/12, diameter diff: +1.77% , speedometer will read slower than actual.
Source : Tire Size Calculator