Bicycle Mechanics - rear derailleur touches spokes
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I have just replaced rear shift cable and now the derailleur is touching the spokes when I use the lowest gear. I tried re-adjusting the the H and L screws but still no luck. Can anyone tell me the steps to fix this?
09-06-08, 08:35 AM
Had you been riding the bike before the cable replacement with out issue?
First thing I would check is to make sure the dérailleur hanger is not bent. I have had this type of issue on more than one bike that I have acquired to flip. I have been able to get things straightened out with a little gentle persuasion and a pair of channel locks.
09-06-08, 10:57 AM
If the hangar is straight, make sure that when you adjust the High and Low limits that you do it with slack in your rear cable. Release the tension from the rear cable pivot, retighten with slack in it, then adjust limit screws by pulling on cable at downtube, remove slack and retighten when limits are set. Tension in the cable makes it hard to see what the actual upper and lower limits are. Adjust limits first with slack, and then remove slack from the cable, and use the barrel adjuster to tweak your indexing after they are set.
09-06-08, 05:13 PM
+1 to above replies. Derailer hanger is the important first step. The point on the hanger where the derailer mounts must be in the same plane as the wheel rim. To actually determine that the wheel must be laterally true and it is most helpful th have a tool similar to the Park DAG-1 for checking/adjusting the hanger alignment. If it is not adjusted properly all bets are off on RD adjustments. Just DON'T RIDE IT WITH THE rd TOUCHING THE SPOKES! Or you will likely need more than some adjustments like a new RD and possible new wheel.
09-06-08, 07:03 PM
Tension in the cable makes it hard to see what the actual upper and lower limits are.
At one point, I was entirely unaware that my derailleur was being held on the small cog purely through cable tension. The limit screw was out far enough that the derailleur could actually pull the chain off the cog and get it caught in the frame.
Thanks everyone for your inputs. I have fixed it and very happy. Here what I did
1. loose the shift cable
2. put the highest gear with biggest chainwheel and adjust the low limit
3. retighten the cable with a bit of slack
4. put the lowest gear with smallest chainwheel and adjust the high limit.
(I kept pushing the shifter to max while adjusting to make sure the the derailer hanger cant
touch the spokes)
2. put the highest gear with biggest chain wheel and adjust the low limitHigh limit screw adjusts the outboard travel limit for high gear(smallest cog)
4. put the lowest gear with smallest chainwheel and adjust the high limit.Low limit screw adjusts the inboard travel limit for low gear (largest cog)
High limit for high gear
Low limit for low gear
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