The standard groove is deliberately wider than the ring in it — by 0.10 mm at most sizes and 0.15 mm at the largest. The retained part can always move that far, even with everything made exactly to nominal.
The clearance has to be there or the ring could not enter the groove and seat. But it means a circlip locates a part rather than clamping it, and every published thrust figure is a static rating that describes nothing about what happens inside that gap.
Under a load that reverses. The gap closes at speed each time the load changes sign, so the ring arrives at the groove wall as an impact rather than a push, and a static rating stops describing the duty at all. The figure also only ever grows: groove width carries a plus tolerance and ring thickness a minus one, so a pair that fully conforms to the standard can float noticeably further than the nominal 0.10 mm.
Estimate with the rule, then check it against the calculator that models it properly.
Open Circlip Calculator →The standard groove is deliberately wider than the ring in it — by 0.10 mm at most sizes and 0.15 mm at the largest. The retained part can always move that far, even with everything made exactly to nominal. The clearance has to be there or the ring could not enter the groove and seat.