Kyosho IFW140-05B Shock O-Ring Set Inferno MP10

This is the O-ring set for Kyosho's Big Bore shocks, the seals that keep oil inside the shock and air out of it.

Shock O-rings are the most important consumable on any oil-filled damper. They ride directly on the moving shaft, which means they are working against friction every single stroke, and they harden and wear from that plus heat cycling and exposure to shock oil over time. When they go, the shock does not fail dramatically. It weeps oil slowly, the fluid level drops, air gets drawn in and foams the oil, and damping quietly falls away over the course of a run. The car feels progressively worse and nothing looks broken.

Because the symptoms creep in, most racers rebuild seals on a schedule rather than waiting to notice. Doing all four shocks at once means they come back matched, which matters more than the absolute damping level.

This is the B revision, superseding the earlier IFW140-05. Kyosho lists it for the Inferno MP10, MP10e, MP11 and MP11e, and dealers extend it to MP9 TKI4 and MP9e applications.