The stock rear tyre size for the Suzuki Gixxer SF 155cc is typically 140/60-17. However, if you're looking to install a wider rear tyre, it's important to consider the compatibility with the bike's frame and swingarm, as well as any potential impact on handling and performance.
While it may be possible to fit a slightly wider tyre, it's recommended to consult with a professional mechanic or authorized Suzuki service center to ensure that the wider tyre will not cause any clearance or handling issues. They will have the expertise to guide you on the maximum recommended width that can be safely installed on your Gixxer SF 155cc model without compromising its performance or safety.