Adjusting the mechanical circuit

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· 10.07.2011

Photo: Dr. Michael Heidelbach

Mechanical gears are characterised by precision and smooth operation - if they are adjusted correctly. In the first part of this workshop, you can read how to adjust the rear derailleur. Part two on the front derailleur will follow in the August issue.

Level of difficulty for interested beginners
Tool Hexagon socket spanner, torque spanner with bits, slotted or Phillips screwdriver

1. shift the chain onto the small chainring and the smallest sprocket - or until no more notch steps are triggered when shifting down. Turn back all cable tension screws completely. The shift cable must be completely slack.

2. view of the rear derailleur from behind: The guide roller must be positioned exactly under the smallest sprocket and form a line with the chain. If not, you must adjust the position with the end stop screw. If the cage of the derailleur pulleys is at an overall angle, the derailleur hanger or derailleur are bent. The repair requires specialised knowledge and tools.

3. the limit stop screws are usually labelled "H" for high gear and "L" for low gear. "H" stands for the high gear ratio, i.e. the small sprocket. If the screws are not labelled, you will have to try them out. If you turn the screw to the right, the rear derailleur moves inwards, if you turn it to the left, it moves outwards. Count the number of turns.

4. carefully (!) check the inner end stop. Slowly turn the crank and push the derailleur inwards with your other hand until the chain runs on the largest sprocket. It must not be possible to push the chain changer any further inwards, otherwise the chain could fall between the sprocket and the spokes.

5. this can damage the rear derailleur and, in the worst case, cause you to fall. Limit the travel of the rear derailleur with the screw for the inner end stop until the chain runs reliably on the largest sprocket. Turn the crank further and release the rear derailleur so that the chain moves back onto the smallest sprocket.

12 Images

Photo: Dr. Michael Heidelbach

TIPS

- Lubrication
If the rear derailleur does not work satisfactorily in any setting, there is usually too much friction in the system. Clean and lubricate the rear derailleur and cables. The Bowden cables may need to be re-routed.
- Fall
If the wheel is tilted to the derailleur side, you must check that the derailleur hanger is still straight and that the inner end stop still limits the swivelling range sufficiently.
- Campagnolo
There are two differences between Campagnolo rear derailleurs and Shimano and SRAM when it comes to adjustment: The limit stop screws are on the outside. And: The distance between the guide pulley and the sprockets is adjusted with the screw on the underside of the rear derailleur, close to the guide pulley axle.
- Test drive
Take a test ride away from road traffic and check the function carefully. If the cables stretch during operation, you can correct this at the next stop using the stop bolts on the head tube or down tube.

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Adjusting the mechanical circuit

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