GAUGE42Si Gold chainline tool by Runwell

The NJS CHAINRING GAUGE measures the 42mm±2mm "standard" chainline on NJS Keirin track bikes. You can also use it to check if a chainring is bent, following an impact or a crash

• Total length 80x35mm
• Weight 28g
• Material stainless steel

Instructions:

As shown in the photo, place the V-groove of the gauge on the seat tube and check distance (42 mm) from the center of the frame to the center of the elongated hole on the gauge. If the installed chainring is positioned within the elongated hole, it meets the inspection requirements.

Note: 
This product was made as a gauge to measure the chain line with a tapered crank. Please note that it may not be possible to measure correctly depending on the width of the BB shell. Also, depending on the hub, the rear sprocket may be out of alignement and the chain line may not be perfect.