It should be possible to size down your wheels without any issue, assuming the smaller size is one that was offered as original equipment by the manufacturer when it was new. You also need to check that the smaller wheels will fit over your brake discs and callipers - if you have a performance model they may be larger than standard. The advantages of the smaller wheel and tyre size should be an increase in ride comfort thanks to the smaller sidewall, it can also result in a small reduction in overall gearing. In terms of disadvantages there will be a small reduction in cornering grip due to the reduced width of the tyre, and your speedometer will be less accurate - although the change in rolling diameter is only 1.43% so this should be within a suitable tolerance.

Kind regards,

David