Yeti 575 Buildout
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Step 14: Installing Rear Derailleur
Attach Derailleur and Chain. Our derailleur is the SRAM X.9 Long Cage. Make sure derailleur hangar is attached to the frame and tightened to spec with lock tight applied to threads. Apply light coat of grease to derailleur attachment bolt threads and attach derailleur to hangar, tightening to spec (70-85 in-lb) with 5 mm hex head. Make sure chain length is correct by mounting the chain onto the largest front chain ring and largest rear cog wheel combination and pulling the unconnected chain together. Now take note of where the two ends meet and add two full links to that length for the proper number of links. Route chain properly through the derailleur being sure to go over the top wheel but inside the metal guards and around the back of the lower wheel or guide pulley. Adjust the Limit Screws. These adjustments set the outer limits of how far your derailleur can move when shifting to either the lowest gear or the highest gear, ensuring your chain will not ride up onto the wheel or axle. This derailleur is standard in that its default position with no tension on the shifter cable is toward the highest gear or smallest cog. Get behind the derailleur and cog/wheel assembly when it's in this position and adjust the high limit screw (marked with an "H") so that the top center line of the derailleur wheel (top tooth) aligns with the outside edge of the smallest cog. Now spin the cranks and push the derailleur with your hand toward the wheel until the chain rides onto the largest cog (i.e. the lowest gear). Adjust the low limit screw (marked with an "L") so that the center line of the derailleur wheel (top tooth) is aligned with the center line (bottom tooth) of the large cog. Route the Shifter Cable. Put a small amount of chain lube on your new shifter cable and slide it through the cable housing and frame-mounts, inserting the free end through the derailluer receptacle and around the elbow through any grooves set up to receive the cable, ending past the pinch bolt. With derailleur in its default position under the smallest cog, lightly tighten the pinch bolt to secure the cable. If your routing takes you underneath the bottom bracket, be sure to leave about two inches of slack there to accommodate movement of the rear triangle on a rear suspension bike, or else your gears will shift as the rear suspension moves over terrain and pulls your cable tight. Set Chain Gap. Adjust the B Adjustment screw. This is the little screw sticking out the backside of the derailleur which pushes the derailleur housing away from the derailleur hangar. It determines the length of the gap between the cog teeth and the derailleur guide pulley teeth. With a 3 mm hex, turn the screw so that this gap is about one-quarter inch (0.25 inches/6 mm) while the chain is riding on the largest cog (lowest gear) and smallest chain ring in front. Turning the B Adjustment screw clockwise makes the gap bigger, or pushes the derailleur down away from the cog. Adjust the Shift Index. Now, with the chain on the smallest rear cog, spin the crank and shift to the next lowest gear. One click should push the chain effortlessly to the next highest cog. If this happens, then shift back to the highest gear again to ensure the chain drops back to the smallest cog effortlessly. If there occurs any roughness or unusual clicking, adjust the barrel adjuster at the shifter to either tighten or loosen the shifter cable with finer granularity. Turning the barrel clockwise turns it in toward the housing and loosens the cable; while turning the barrel counterclockwise moves the barrel out away from the housing and puts more tension on the cable, thus moving the derailleur toward the larger cogs. Tune the tension with the barrel adjuster until the chain shifts back and forth seamlessly from the smallest cog to the next largest cog with one click of the shifter in either direction. Once this adjustment is finished, all the other gears ought to "fall into place" in that each click of the shifter should put the chain smoothly onto the next cog until the low limit adjustment screw keeps the derailleur from moving any further past the largest cog (lowest gear). Once the derailleur is indexed and shifting to your satisfaction, cap the cable with crimpers leaving an inch and a half to two inches of cable past the pinch bolt.
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