In our latest look at how to tune your bike, we look at how to adjust a rear dérailleur correctly. It is not really important which brand the derailleur is, as all brand are similar, some screw might be located differently, but overall the function is the same.
Bagnoli Bike took us through the steps necessary to make a correct adjustment.
Tools needed: 5mm Allen wrench, Phillips screw driver (Shimano), 2.5mm Allen wrench (Sram), a bike stand is useful, good vision…
Firstly disconnect the rear gear cable on the derailleur end.
When it is properly disconnected make a check of the cable and ensure like in the photo above it is not frayed or damaged, if so replace the cable inner.
Check the dérailleur is attached to the bike correctly and the gear hanger is straight, use a large Allen wrench to straighten the hanger if slightly out of true.
Pedal the bike and check that the dérailleur sits in the bottom gear without any noise or chain chatter, if not adjust the H screw until it is positioned perfectly and makes no noise.
Wind back in the adjustment barrel on the gear shifter and make sure the shift is in the last gear position. (10th or 11th in most cases.)
Reconnect the cable to the dérailleur.
The cable should not be pulled tight but should not have any slack.
Start to pedal the bike and shift the gears up the cassette, each click should mean the gear shifts one up.
Get to the lowest gear (the biggest rear sprocket) and make sure that the chain moves easily on to the largest sprocket with out jumping over it.
Use the L adjustment screw to make sure the chain shifts into 1st gear, the screw acts like a block on the derailleurs movement. Once correct the derailleur will sit in first gear and pedal smoothly the same as in 10th gear.
If the gears are slow to respond or not being as they should the B-tension screw that control jockey wheel closeness to the cassette block needs checking and adjusting. In the photo above we can see the gap between the top of the chain and the first gear is too big, (the ideal is 3-4mm).
Use the screw driver to adjust the B tension screw so it moves the dérailleur top jockey wheel in the direction of the cassette if it is too far.
Here it is correctly adjusted to around 4 mm. It is important to note that between Sram and Shimano derailleurs, Sram are more sensitive to smooth gear changes by having the B-tension screw correctly adjusted.
The key to an overall package of smooth gear changes is a clean chain, components that are in a good condition and everything is aligned properly. A worn cassette or chain is often the cause of poorly shifting gears, as is a sticky cable. Follow the steps above to make sure that all is in alignment.