today I was surprised when I found this forum. I search for tire size informations and winter tires options, and I have found some very useful informations here.
I have summer tires, as manufacturer specifications recommendation: 205/60/R16, and here where I live, is really hard to find winter tires with that dimensions, so I must use an alternative. There are two options:
1. To buy 195/55/R16 tires, or
2. To buy new rims with R15, and mount on it tires 195/60/R15
The price is similar in both cases, but in 2. I would get additional R15 rims.
(R16 tires price ~ R15 tires + rims price)