During my recent search for 16" FR tyre I could feel the pinch of choosing a rather slow moving SKU. The difference in cost is atleast Rs.1500 between fast moving 15" and slow moving 16". Also I had found that the 15" rim costs around 1.3-1.5 k only. So my new tyre changes and overall maintenance costs reduces and also I don't lose much on ride quality. The recent pain of using a lower sized stepney and impossibility of tyre rotation has made me think this way (or I've to buy one 16" rim to be put as stepney). As @Turbothinghy pointed even I didn't feel any difference in ride quality between a 75 HP and a 90 HP through rough roads. Only difference was that the 75Hp had lower under thigh support and 90 HP has still much lower under thigh support. So the choice is opened up when one opts for 15" wheels and tyres compared to those of 16". (I'm not a big fan of alloys but not against in owning one that comes as stock. I will not splurge on new sets of alloy. So if not this tyre change next at around 1lac+ on ODO i will choose a 15").