Many bicycles use the Shimano cassette system for rear wheel gears. Compared to the older freewheel system, which threaded onto the wheel hub, the Shimano cassette uses a single spline lock ring to hold a cassette of sprockets in place on the wheel. This system makes changing to a different set of gear ratios or replacing worn gears easier.
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Shift the rear gears to the smallest sprocket on the Shimano cassette. Open the quick-release lever to loosen the axle. Remove the rear wheel from the bicycle. Unscrew the acorn nut from the quick-release skewer and remove the skewer from the axle.
Place the chain whip around the largest sprocket on the cassette in a clockwise direction to hold the cassette in place when loosening the spline lock ring.
Insert the spline lock ring tool pin in the axle hole so that the tool aligns with the notches in the cassette.
Place the adjustable wrench on the hexagonal end of the spline lock ring tool. Hold the chain whip handle in one hand and the adjustable wrench handle in the other. At the same time, turn the chain whip clockwise and the wrench counterclockwise to loosen and remove the spline lock ring.
Remove the chain whip from the cassette. Pull the cassette out and away from the wheel to remove it from the freehub body.
Check the freehub body to ensure that it spins freely and easily but is not loose.
Align the splines of the new cassette with those on the freehub body to install the cassette. Install the smallest sprocket, and insert the spline lock ring tool into the new spline lock ring. Insert and thread the spline lock ring and tool clockwise into the freehub body.
Set the wheel on edge so the tread of the tire is firmly on the ground. Tighten the lock ring with the adjustable wrench. Check the new cassette to ensure that it is not loose and spins freely.
Replace the quick-release skewer in the axle, thread on the acorn nut and reinstall the wheel on the bike.