Workshop: Correct sprocket mounting

Dan Hooper

· 21.09.2014

Photo: Georg Grieshaber

Workshop: Correct sprocket mounting

Every DIY workshop has a screwdriver botch-up. Super-Dan, the saviour of all hobby mechanics, is here to help. This time he shows you how to correctly fit a 40 or 42 mm mountain sprocket.

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For snap-breathing fans of the 1x10 drivetrain concept, a special mountain sprocket can be a saviour on steep climbs. But 29er riders or bikers with double cranks can also benefit from a 40 or 42 mm "pizza plate". Many manufacturers now offer the extra-large slip-on sprockets for retrofitting. However, before you can convert your bike to be suitable for ramps, you should consider a few points. Check whether your cassette is suitable for the conversion. There should be no problems with Shimano XT and XTR as well as Sram X5, X7 and X9. Your rear derailleur must also have sufficient capacity. A medium cage usually only works with a single chainring. For double drivetrains, you need a rear derailleur with a long cage. Rear derailleurs with a short cage do not have sufficient capacity for such large sprockets.

1. attach the chain whip and the cassette puller to the cassette and loosen the cassette end ring. You can then remove the cassette from the freewheel. Now remove the 17 mm sprocket and the corresponding spacer ring. With some sprocket sets, you also have the option of removing the 15 mm sprocket.

2. now the 40 or 42 sprocket, depending on which model you have chosen, is slid onto the freewheel body first. This is followed by the other sprockets. Pay attention to the correct sequence when assembling. The cassette is then secured again with the cassette end ring with a torque of 40 Newton metres.

3. you must now use the wrap screw to correctly adjust the distance between the rear derailleur and the sprockets. To do this, shift to the largest sprocket and turn the wrap screw in until the upper derailleur pulley is a few millimetres below the large sprocket. The derailleur pulley and sprocket should be directly in line.

4. with many rear derailleurs, the length of the wrap bolt will not be sufficient for a 40 or 42 sprocket. Some manufacturers supply a longer bolt for this purpose. Replacements are also available cheaply from DIY stores. An M4 Allen screw with a length of 20 millimetres should be sufficient. You should use stainless steel for the material.

Super Dan's tip: If the rear derailleur still has problems shifting the largest sprocket, check the chain length. For double drivetrains, place the chain on the large chainring and the largest sprocket and add two chain links. With single drivetrains, the derailleur cage should not be fully tensioned on the large sprocket, but should have some play at the top.

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Photo: Georg Grieshaber

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