Bicycle Chain Sprocket Guard - 185mm diameter

I had trouble finding a chain guard for my bicycle on the market. I checked a couple of second-hand shops and local stores but came up empty-handed. Eventually, I was left with one option: 3D printing.

I wasn’t in the mood to disassemble the chain sprocket to model it from scratch, so I searched Printables and Thingiverse first. Luckily, there were plenty of available designs to choose from. To find the right fit, I printed four-layer slices from the middle of models with four attachment holes to use as templates and check if the holes lined up with my bike.

This model turned out to be exactly what I needed. Initially, I modified the .stl file so I could print it lying flat without supports. In my case, there was no need to tweak the .scad file, but I was ready to do so if needed.

During testing, I noticed that when shifting gears, the chain occasionally slipped between the largest sprocket and the guard. To solve this, I designed a slanted cone guide to push the chain back onto the sprocket when that happens. I didn’t want to reprint the entire guard, so I printed the guide separately and glued it onto the original model.

I’m sharing both versions here for you to experiment with and find the solution that works best for your bike.

Thanks to the original creator for this great base design!