Degree of difficulty: for talented hobby mechanics
Tool:
- Hexagon socket spanner, torque spanner with bits, slotted or Phillips screwdriver
Excipients:
- Carbon assembly paste
TIPS:
Cross-checking
With Shimano front derailleurs, check the correct tension by shifting to the largest chainring and largest sprocket. When the trim level is relaxed (if available), the front derailleur must not be more than 0.5 millimetres away from the chain.
Function test
Test the gear setting thoroughly before riding! While the bike is hanging on the assembly stand, shift from the large to the small chainring several times with changing crank speed when the largest sprocket is on the rear. Repeat the test with the chain on the smallest sprocket.
Test drive
After the adjustment, take a test drive away from traffic and shift through all gears again.
Control
Check the screws of the cable fastenings and the fastening of the rear derailleur and front derailleur with a torque spanner according to the specifications of your gear manufacturer after 100 to 300 kilometres of riding, then every 2,000 kilometres.
CHECK POSITION
1
Shift to the largest sprocket and the smallest chainring. The lower edge of the front derailleur guide plate should run evenly about two millimetres above the large chainring. Some modern chainrings have differently shaped teeth - the highest ones are the benchmark for the distance!
2
Look at the front derailleur and chainring from above, front and rear. The outer guide plate must be parallel to the chainrings. If you find it difficult to judge, press the shift lever lightly so that the guide plate is directly above the tooth tips.
3
If one of these two conditions is not met, slacken the derailleur cable by shifting to the small chainring. Loosen the fixing screw of the front derailleur on the frame mount or on the clamp on the frame by turning it one or two turns anti-clockwise.
4
Adjust the front derailleur and hold it in the correct position. Tighten the screw again according to the manufacturer's recommendation (usually 5 to 7 Newton metres for base mounting).
5
Clamps on carbon frames 6 must be tightened carefully. Start with 2.5 Newton metres and increase in steps of 0.5 Newton metres until the clamp is securely tightened.
6
If the front derailleur is still not holding at 3.5 Newton metres, apply carbon assembly paste to the inside of the clamp. Then check again whether the guide plate is now correctly aligned.
ADJUSTING THE EJECTOR
1
Check the distance between the inner guide plate and the chain when the tension is relaxed (chain on the small plate). To do this, turn the crank - the chain must not rub, but the distance must be as small as possible. A gap of more than half a millimetre can cause the chain to be thrown off when shifting gears. Adjust the distance using the internal end stop screw.
2
This screw is usually difficult to turn because the front derailleur rests on it with high spring force; relieve the screw by swivelling the front derailleur cage slightly outwards by hand. Turn the inner screw clockwise a quarter turn until the position of the front derailleur is correct.
3
Check the cable tension: To do this, the tensioning screw of the front derailleur cable on the down tube or head tube must be screwed in all the way and the shifter must be relaxed (chain on the small chainring). Pull the cable away from the down tube as a test - the derailleur should then move as directly as possible.
4
If this is not the case, unscrew the tensioning screw (Fig. 5) on the clamp one turn. Tighten the cable by holding it firmly, opening the cable clamp bolt (Fig. 4) by one or two turns, pulling the cable taut and clamping it again (torque 5 to 7 Newton metres). Shift to a middle sprocket and the large chainring.
5
If the chain does not climb, the tension is still too low. Tension the cable with the tensioning screw on the head tube or down tube by half a turn anti-clockwise. Try shifting to the large chainring again. Tighten the cable until this works without any problems.
6
Leave the chain on the large chainring and shift to the smallest sprocket. The front derailleur must be adjusted as closely as possible to the chain so that it is not thrown outwards. Shift to the small chainring. Turn the outer limit stop screw in a quarter of a turn. Shift up again. Repeat this until the setting is correct.
Further workshop tips can be found in the standard work "The road bike workshop" retail price 14,90 Euro
TOUR author Dirk Zedler is the owner of the Zedler Institute for bicycle technology and safety GmbH. Zedler - Institut für Fahrradtechnik und -Sicherheit GmbH specialises in testing bicycles and components in its own test laboratory. The company also develops and builds test systems and equips test laboratories for bicycle manufacturers.
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