At work, I often need to quickly check the chainline of a crankset assembly. The ChainLineR is a simple gauge designed to make this process faster and easier, allowing you to measure your bike’s chainline and verify if it’s within the recommended specs for Shimano, SRAM, or Campagnolo.
The model 
The 3D print 
On a fixed gear bike 
On a road bike with 2x crankset
While you can use a caliper to do this, it can be tricky to find a clear reference point to identify the center of the seat tube (e.g., the bottle cage bolt). The V-shaped design of the ChainLineR allows you to quickly center it on the seat tube or downtube, providing a rough but reliable reading of your chainline using millimeter markings.
An additional stopper allow you to place a ruller and get a more accurate read.
How to use:
- Position the ChainLineR on any symmetrical part of your bike—ideally the seat tube or downtube.
- Use the millimeter markings to read the chainline measurement.
Notes:
- Some tubes may be asymmetrical.
- The chainline for 2x setups is measured differently depending on the manufacturer. For example, Shimano measures from the inside of the larger chainring’s teeth.
Thingiverse:
https://www.thingiverse.com/thing:5519359