Wrong derailleur hanger?
01-23-08, 02:14 AM
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Wrong derailleur hanger?
The cogs on my cassette are either close to hitting or hitting the derailleur pulley in almost all gears. The b-tension screw is all the way in. I even tried another derailleur, - same thing. The chain seems to be the correct length.
The bike is a Specialized Allez with a replaceable hanger. I picked up this bike used. Is it possible it's got the wrong hanger on it? Anybody heard of this happening? It's like the derailleur cage is just too close to the cogs.
The bike is a Specialized Allez with a replaceable hanger. I picked up this bike used. Is it possible it's got the wrong hanger on it? Anybody heard of this happening? It's like the derailleur cage is just too close to the cogs.
01-23-08, 05:51 AM
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In my experience this is often caused by the characteristics of certain frames. Check how much a bearing the screw has on the tiny platform of the hanger. Sometimes it can be improved by replacing the screw with an Allen headed bolt but on one of my steel bikes I used a Arc welder to build up the platform on the hanger.
01-23-08, 06:37 AM
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You have checked the length of your chain, correct?
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72 Frejus (for sale), Holdsworth Record (for sale), special CNC & Gitane Interclub / 74 Italvega NR (for sale) / c80 French / 82 Raleigh Intl MkII f&f (for sale)/ 83 Trek 620 (for sale)/ 84 Bruce Gordon Chinook (for sale)/ 85 Ron Cooper / 87 Centurion IM MV (for sale) / 03 Casati Dardo / 08 BF IRO / 09 Dogma FPX / 09 Giant TCX0 / 10 Vassago Fisticuff
01-23-08, 09:01 AM
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Derailleur hangers usually have a small lip on them that the B-screw drives into and, as a result, gives the adjustability that you are supposed to get from that screw.
Just sight down the B-screw and see if there is a little lip that it is driving into. If not, then you have a problem. I have seen a lot of bikes that were not correctly assembled and the B-screw has missed the lip and the result is rubbing cassettes&jockey_wheels in the large_cog/large_chainring combination. This could be from:
1. The derailleur hanger not being installed in the correct alignment with the frame.
2. The rear derailleur not being installed correctly, and the B-screw is missing the derailleur hanger lip (and against the very tip of that lip). This is most likely.
3. The wrong derailleur hanger has been installed.
4. Bad design. This is essentially the same as my reason #3, but that case is accidental, and this case is just a bad frame/hanger combination used by the manufacturer. I am seeing brand new bikes that you just can't adjust to accommodate for the worst case gear combinations. Yes, this would be cross chaining, and, yes, you're not supposed to do that. But, you still should be do the proper B-screw adjustment.
OK, I may have missed something, but that's as much as I can think of at this time. If it does not look right, it's not a bad idea to take your 5mm hex wrench and remove the rear derailleur and then re-install it.
While you're at it, check to make sure that the fastener that holds the derailleur to the frame is tight. It needs to be firm, but not killer tight. This is an easy one to strip and you can ruin a frame.
Just sight down the B-screw and see if there is a little lip that it is driving into. If not, then you have a problem. I have seen a lot of bikes that were not correctly assembled and the B-screw has missed the lip and the result is rubbing cassettes&jockey_wheels in the large_cog/large_chainring combination. This could be from:
1. The derailleur hanger not being installed in the correct alignment with the frame.
2. The rear derailleur not being installed correctly, and the B-screw is missing the derailleur hanger lip (and against the very tip of that lip). This is most likely.
3. The wrong derailleur hanger has been installed.
4. Bad design. This is essentially the same as my reason #3, but that case is accidental, and this case is just a bad frame/hanger combination used by the manufacturer. I am seeing brand new bikes that you just can't adjust to accommodate for the worst case gear combinations. Yes, this would be cross chaining, and, yes, you're not supposed to do that. But, you still should be do the proper B-screw adjustment.
OK, I may have missed something, but that's as much as I can think of at this time. If it does not look right, it's not a bad idea to take your 5mm hex wrench and remove the rear derailleur and then re-install it.
While you're at it, check to make sure that the fastener that holds the derailleur to the frame is tight. It needs to be firm, but not killer tight. This is an easy one to strip and you can ruin a frame.
Last edited by cascade168; 01-23-08 at 09:02 AM. Reason: correctness
01-23-08, 07:41 PM
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01-23-08, 09:44 PM
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Derailleur hangers usually have a small lip on them that the B-screw drives into and, as a result, gives the adjustability that you are supposed to get from that screw.
Just sight down the B-screw and see if there is a little lip that it is driving into. If not, then you have a problem. I have seen a lot of bikes that were not correctly assembled and the B-screw has missed the lip and the result is rubbing cassettes&jockey_wheels in the large_cog/large_chainring combination. This could be from:
1. The derailleur hanger not being installed in the correct alignment with the frame.
2. The rear derailleur not being installed correctly, and the B-screw is missing the derailleur hanger lip (and against the very tip of that lip). This is most likely.
3. The wrong derailleur hanger has been installed.
4. Bad design. This is essentially the same as my reason #3, but that case is accidental, and this case is just a bad frame/hanger combination used by the manufacturer. I am seeing brand new bikes that you just can't adjust to accommodate for the worst case gear combinations. Yes, this would be cross chaining, and, yes, you're not supposed to do that. But, you still should be do the proper B-screw adjustment.
OK, I may have missed something, but that's as much as I can think of at this time. If it does not look right, it's not a bad idea to take your 5mm hex wrench and remove the rear derailleur and then re-install it.
While you're at it, check to make sure that the fastener that holds the derailleur to the frame is tight. It needs to be firm, but not killer tight. This is an easy one to strip and you can ruin a frame.
Just sight down the B-screw and see if there is a little lip that it is driving into. If not, then you have a problem. I have seen a lot of bikes that were not correctly assembled and the B-screw has missed the lip and the result is rubbing cassettes&jockey_wheels in the large_cog/large_chainring combination. This could be from:
1. The derailleur hanger not being installed in the correct alignment with the frame.
2. The rear derailleur not being installed correctly, and the B-screw is missing the derailleur hanger lip (and against the very tip of that lip). This is most likely.
3. The wrong derailleur hanger has been installed.
4. Bad design. This is essentially the same as my reason #3, but that case is accidental, and this case is just a bad frame/hanger combination used by the manufacturer. I am seeing brand new bikes that you just can't adjust to accommodate for the worst case gear combinations. Yes, this would be cross chaining, and, yes, you're not supposed to do that. But, you still should be do the proper B-screw adjustment.
OK, I may have missed something, but that's as much as I can think of at this time. If it does not look right, it's not a bad idea to take your 5mm hex wrench and remove the rear derailleur and then re-install it.
While you're at it, check to make sure that the fastener that holds the derailleur to the frame is tight. It needs to be firm, but not killer tight. This is an easy one to strip and you can ruin a frame.
The derailleur looks to be on alright. I'm not sure how it could go on any other way.
01-23-08, 09:45 PM
#8
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See this site (https://www.derailleurhanger.com/) and compare the recommended hangar with yours. The site doesn't offer dimension, but perhaps you can judge by visually comparing the two. At worst, you can order one from the site that is intended for your bike.
