SETTING UP TRANSMISSION

A silent, smooth-running transmission can make all the difference to your ride. Follow our 16-step guide carefully and you’ll get it right every time

(01) FIND STOP SCREWS

With the front mech in place and the chain removed, locate the stop screws marked H (high) and L (low). On a top-swing front mech, the L screw is the inner screw, controlling the limit of the mech’s inward motion. The high screw is the outermost screw and limits the mech’s outward motion. On a bottom-swing mech, this is reversed. They are adjusted with a Phillips screwdriver.

(02) SET FRONT SCREWS

Set the L screw so that the front mech cage’s inner plate is roughly 4mm from the smallest chainring. Then, pushing the mech cage out by hand, set the H screw so that the outermost plate of the mech cage is 4mm from the outside of the big chainring.

(03) SET REAR SCREWS

Similarly, roughly set the rear mech’s H and L screws. Turning the screws anti-clockwise allows the mech to move towards the spokes, and clockwise moves it away from the spokes. The top jockey wheel of the mech should stop directly under the largest cassette sprocket, adjust the L screw to do this, and directly below the smallest cassette sprocket, adjust the H screw.

(04) B! ANGLE SCREW

Most rear mechs have a third screw — called either the B-tension or B-angle screw — which adjusts the clearance between the top jockey wheel and cassette sprockets. With a Phillips screwdriver, adjust it for a distance of 5-6mm. This ensures that when you put the chain on, it will be close enough for quick shifting yet clear enough to pass freely from the second largest sprocket to the largest.

(05) FIT GEAR CABLES

Apply a light lube to the gear cable outers to help ensure the free running of the gear cable. Then, thread a new, clean gear cable through the bar-mounted shifters and through the gear outers for both the front and the rear mech.

(06) SET FRONT CABLE

With the front shifter set on the lowest gear position (normally marked 1), run the gear cable through the anchor bolt of the front mech. Pull it taut using a pair of pliers at the same time as you tighten the anchor bolt. Push the gear shifter a few times to seat the cable properly, then loosen the anchor bolt and take up the slack before re-tightening the bolt.

(07 ) SET REAR CABLE

With a normal rear mech, set its shifter on the lowest gear position. For a Low Normal/RapidRise mech that springs to the smallest sprocket, set it to the highest gear position (usually marked 8 or 9). Thread the cable through the anchor bolt and hold the cable tight with pliers before fastening it. Push the shifter a few times to seat the cable. Then loosen the bolt, take up the slack and re-tighten.

(08) CHAIN LENGTH

To get the correct chain length, bypass the rear mech and thread the new chain around the big ring and the biggest rear sprocket. Bring the chain ends taut and together, and add three whole chain links. Remove any excess length of chain using a chain tool. This should give you the correct chain length for your gearing.

(09) THREAD THE" CHAIN

Thread the new chain through the front mech cage, over the cassette sprockets, over the top jockey wheel, through the rear derailleur cage and around the lower jockey wheel correctly. Drop it off the big ring to rest on the bottom bracket shell and onto the smallest cassette sprocket. This will give you enough free links to easily connect the chain together.

(10) JOIN THE CHAIN

For Shimano, bring the links together and insert a Shimano joining pin. Press the pin into place with a chain tool and snap off the protruding guide pin with pliers. For SRAM and KMC chains, use the PowerLink to connect the chain by slotting each half of the link through each end of the chain. Bring them together to snap the two pin halves of the link together. Pull the halves to securely seat the link.

(11) CHECK THE CHAIN

With the chain in place, check the front and rear mech stops. The front mech plates should clear the chain by 2mm. If there’s any rubbing, fine-tune the H/L screws to move the mech plates, but make sure that the chain cannot get dumped off the small or large chainring during a rapid shift. The rear mech jockey wheels should be directly beneath the largest and smallest sprockets at their H and L limits.

(12) GEAR INDEXING

Once the stop and B-angle screws are adjusted, the rear mech’s indexing can be sorted. This is done by changing the tension of the gear cable at the barrel adjuster, which is on both the shifter and rear mech for Shimano, and at the shifter only for SRAM. Shift the chain to the largest chainring and shift the rear mech by one click. If the shift occurs smoothly, cable tension is adequate. If it doesn’t, it’s too slack.

(13) REMOVES LACK

Turn the barrel adjuster all the way in – at the rear mech or the shifter – and then turn anti-clockwise by two turns to allow for any adjustments. Loosen the inner wire pinch bolt and gently pull through any cable slack using a third-hand tool or a pair of pliers. After that, tighten the pinch bolt.

(14) TENSIONS OS

If the mech won’t shift one sprocket after removing the slack, change the shifter to the highest gear position. Increase cable tension by turning the mech’s barrel adjuster or shifter anti-clockwise by a quarter turn. Shift to second smallest sprocket. Turn the pedals and increase tension by turning the barrel adjuster anti-clockwise until you hear rattling, this is the chain scraping against the next sprocket.

(15) REMOVING THE" RATTLE

Once this rattle occurs, turn the barrel adjuster clockwise by a quarter turn to release the cable tension, and then pedal again. Listen and look for signs of chain scraping and/or rattling, and continue to turn the barrel adjuster clockwise by quarter turns until the rattling disappears.

(16) FINAL CHECK

Shift by one sprocket at a time from the smallest cog to the largest, listening and looking for signs of rattling to indicate a too-tight inner cable tension. Turn the barrel adjuster clockwise by a quarter turn at a time to eliminate any rattle. Shift the front mech to the smallest chainring and check the gears. If there’s no rattling or chain rubbing, the gears are indexed. Lube the chain and you’re ready to ride.