Replacement shocks are designed to fit into the same dimension as the OEM part. If your replacement shock doesn't fit it's not correctly designed for your bike. Less than one inch is a huge difference. It will alter many aspects of the bike (ride height, head angle, trail, etc.). Any change to...
What is the stock c-c dimension of shock bolts on a 2015? It's approximately 300mm on a 2018. If it's 300mm on a 2015 I would think a 285mm replacement would not work.