Our friends over at MAHLE Motorsports are a wealth of information; their work as an OE piston supplier affords them engineering and usage data that’s leaps and bounds above what they’d get as an aftermarket manufacturer alone. In this video, MAHLE’s Bill McKnight offers up some tips on how to measure the three different critical piston ring dimensions using a dial caliper, and the importance of those dimensions to selecting the proper piston ring.

Knowing the exact bore of the cylinder, along with the ring’s radial wall thickness and face width are the most important dimensions to be aware of – because too small or too large and the replacement ring won’t perform properly, or worse, won’t fit into the piston or bore at all. With measurements running into the thousandth of an inch, it’s important to be able to measure the ring with precision. A simple pair of six-inch dial calipers can be had at a place like Harbor Freight for under $25 make them an essential part of your toolbox.

MAHLE’s Bill McKnight walks us through the measurement process, talking about the differences between inch-to-millimeter conversion and how to determine each. This may seem elemental to some, but knowing how to determine these dimensions is important, especially at engine rebuild time, when you can’t find the box or the packing slip from your original piston rings – and we’ve all been there. MAHLE has a number of other helpful videos on their YouTube channel – check ’em out!

For more information on the complete line of MAHLE Motorsports products, check out their website.