GAUGE42S 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 the chainrings, which may bend due to an impact after a fall.

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

As shown in the photo, place the V-groove of the gauge on the seat tube and check length (42 mm wide) from there to the center of the elongated hole on the right side. If the installed chainring is positioned within the elongated hole, it meets the inspection requirements. Especially when using a tapered crank, the tapered part may rub too much and be pushed deeper than necessary.

Also, there are cases where the crank is not fully tightened so please use GAUGE42S in such situations and check that the chainring is in the appropriate position.