A worn Shimano or SRAM cassette lockring can be properly stuck. Forty Nm of factory torque plus a season of corrosion plus a freehub that's been hosed off and dried in dirt adds up to a lockring that doesn't move on the first push. The 1670.8/2BI-US is the cassette-removal tool that doesn't make you build a stack of adapters to break it free: a Shimano/SRAM-pattern 12-spline socket, a centering guide pin, and a long bi-material handle, all in one piece. The guide pin is the design choice that does the work. A bare lockring socket without a centering pin sits in the splines under load and wants to walk; the first hard pull and it's popped out, with rounded spline corners as the parting gift. The guide pin slides through the lockring's central bore and through the wheel's quick-release skewer hole, anchoring the tool against the wheel itself. The splines stay seated through the break-free, no matter how stuck the lockring is. The bi-material handle is the leverage half of the equation. Tools designed to be paired with a ratchet are sized for the ratchet's leverage, not the lockring's resistance; an integrated handle solves the leverage problem at the source. The 1670.8/2BI-US's handle is long enough that a hand at the end of it puts the lockring well past the torque it was installed at. The bi-material grip stays grippy under the hand pressure that those torque values require. How to use it Slide the guide pin into the lockring's bore and through the wheel's QR or thru-axle channel. Snug the QR or axle nut against the back face of the tool; this stops the tool from popping out under load. Hold the cassette still with a chain whip or Cassette Wrench on the larger cogs. Pull the handle counter-clockwise. The break-free is usually one firm motion. Loosen the QR or axle a quarter turn each time the lockring breaks free further and the tool wants to lift, and you'll thread the lockring all the way out without resetting your stance. Compatibility Shimano HG cassettes, 7- through 12-speed SRAM HG cassettes including XD and XDR (lockring pattern matches HG) Microshift and Sunrace cassettes using the Shimano HG lockring pattern Not for Campagnolo (use 1670.4/4) Not for thru-axle hubs without a removable axle (the guide pin needs the bore) Specs 12-spline Shimano/SRAM HG lockring pattern Centering guide pin (slides through the cassette lockring bore) Integrated bi-material handle Trivalent chrome plated to ISO 1456:2009 Article number: 1670.8/2BI-US Built in Zreče, Slovenia Unior has been forging hand tools in Zreče since 1919, and sponsors professional road and mountain-bike race teams. The 1670.8/2BI-US is the highest-leverage integrated-format cassette tool in the catalog; the design call is that the workshop should not have to assemble a stack of three pieces; socket plus ratchet plus guide adapter; when one tool can do the same job. The handle's bi-material grip is a small detail, but it's the difference between a tool that works and a tool that hurts your hand under the force a stuck lockring takes to move. Pro tip from our mechanics Reinstall is the half of the job that gets done wrong. The same guide pin that protected the splines on removal protects them on reinstall; leave the tool seated through threading until the lockring touches down on the freehub, then back off and torque to spec with a wrench on the 1670.8's handle. Shimano publishes 40 Nm for HG cassette lockrings; SRAM publishes 35–45 Nm depending on cassette tier. The cassette-replacement workflow has the torque values per drivetrain and what happens when you skip them: When and how to replace your cassette → FAQ Which cassette lockrings does the 1670.8/2BI-US fit? It drives the splined lockring pattern shared by Shimano, SRAM, Sun Race, Suntour, and most other cassette brands. Campagnolo lockrings use a different spline — for those, Unior makes the 1670.4/4 Campagnolo Cassette Lockring Tool. Do I still need a chain whip to remove a cassette with this tool? Yes, for removal. The lockring tool turns the lockring; something has to hold the cassette against the freehub's ratchet, so pair it with a chain whip or the Unior Cassette Wrench on the larger cogs. Reinstalling needs no whip — the freehub ratchet holds the cassette while you tighten. Will it work on a thru-axle wheel? The centering guide pin is 5.0 mm, sized to pass through a quick-release skewer channel, so a thru-axle hub needs its axle removed first. If your fleet is mostly 12 mm thru-axle, the purpose-built option is Unior's 1670.9/4 Cassette Lockring Tool with 12 mm Guide. How big is the 1670.8/2BI-US, and what is it made of? It is 337 mm long overall and weighs 340 g, with a 23.6 mm splined head and a 5.0 mm guide pin. The steel is trivalent chrome plated, the handle sleeve is two-component for grip, and like all Unior hand tools it carries a lifetime warranty.
