I suppose the easiest way would be to offer them into a cylinder of known dimensions – allowing of course for the appropriate gap.
Other than that, if you trot along to your nearest friendly piston stockist, they will have a piston diameter measuring device (usually on the counter)which will also tell you the size of the rings.
Whilst rabbiting on a note of caution.
Do NOT use filed-down oversize rings, as the radial pressure exerted on thecylinder wall will not be uniform, so they won’t seal properly.
Listen to Stanley – you know it makes sense.
Stan Thomas.
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