The Bilstein B6 24-155335 is a rear-axle monotube shock with a 46mm body, built on Bilstein's gas-pressure damper design. The manufacturer positions the B6 line as a performance upgrade that pairs with factory springs, using application-specific valve settings and a velocity-sensitive digressive piston that keeps damping consistent under sustained hard use. Compared with conventional units, the monotube layout is meant to resist fade during repeated spirited driving, such as canyon runs or track days.
Owners on user forums describe a firmer, more composed rear end than stock, with better control when the trunk or rear seats are loaded, though some find the ride noticeably stiffer. For Lexus IS F owners wanting sharper response on the rear axle without a full coilover conversion, this is a practical middle ground. Forum discussions also cite a lowering limit of roughly 30mm when paired with shorter springs, but details vary, so confirm with the manufacturer before planning a lowering setup. Search terms like Lexus IS F rear monotube shock, USE20 B6 damper, and IS F rear shock upgrade will lead you to this exact application.
The manufacturer designs the B6 to pair with the factory springs, so new springs are not required for a stock-height setup.
User forums report that the manufacturer's guidance allows up to about 30mm of drop with shorter springs. Details vary between sources, so confirm the limit with the manufacturer before installing.
Owners on user forums say yes. The rear is tighter to access, and the lower mount is harder to seat because the new bushings are thicker than stock, so a second person is strongly recommended.
This is a moderate-difficulty rear job that most home mechanics can complete with a full socket set, extensions, trim tools, lithium grease, and a plastic hammer. Owners on user forums report that the top mount bolts are reached from inside the cabin, which typically means removing the rear seat back and its trim clips and lifting the rear package tray for access. The lower eye can be stubborn, so a helper to guide the shock into position makes the job much easier. Before you start, soak seized fasteners in penetrating oil, since rust is a common complication on older vehicles. Because the rear seat is disturbed, many owners take the chance to replace the sway bar bushings while they are underneath.
