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Rear derailleur angle

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Rear derailleur angle

Old 10-01-21, 06:30 AM
  #1  
Cm69.gb
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Rear derailleur angle

Hi, new to this forum so please be gentle. Im trying to fix up an old bike and have removed the back wheel, cleaned the cassette and chain and then put it back on.

however now I have the wheel on the derailleur is not looking right. When I shift to the top gear the derailleur is almost folded back on itself and the two jockey wheels are rubbing against each other

there is only one way the derailleur can fit on and I cant see any screws to adjust that angle as the limiter screws dont make any difference to moving the jockey wheels down

when I manually move the jockey wheels down to where I think they should go, the chain goes slack

the chain and derailleur are the same as was on the bike before I removed the wheel. Any ideas?
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Old 10-01-21, 07:13 AM
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My first thoughts are:
- did the rear derailleur shift properly prior to your removing the wheel, or is this your first time evaluating the shifting performance on this bike?
- if the answer is "yes", then the chain is too slack. Don't assume that the bike had the correct chain length from when you purchased it. Check:
(1) is the lower pivot spring forcing the lower pulley backward with sufficient force? The spring has a pin that is anchored in a hole on the backside of its housing. This pin can shear off or snap with fatigue.
(2) shift onto the innermost, largest cog, and then carefully onto the largest chainring up front. The chain should just barely permit this combination. How many links (2 half-links = 1 link of 1") of the chain could you conceivably remove and have the chain still reach?
(3) this rarely happens, but the angle of the derailleur mounting may be incorrect. Typically, there is a stop cast into the frame's rear dropout at about the 7 or 8 o'clock position, and there's a corresponding tab beneath the derailleur mounting (or upper pivot) bolt that engages that dropout stop. Some older bikes do not have those stops, but rely on a different way to clamp the derailleur into position. (A photo would help here) Additionally, many (but not all) derailleurs have a spring loaded within the upper pivot (mounting) bolt, and that helps to maintain the correct overall rearward tension on the derailleur (again, photo, or at least read the derailleur part number from the inner parallelogram long plate).

Those are where I'd begin. PG

Last edited by Phil_gretz; 10-01-21 at 08:14 AM.
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Old 10-01-21, 08:23 AM
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It is possible to mount a derailleur incorrectly on the hanger.
I think you need to tell us more info
Brand of bike
model of bike
year of bike
Derailleur brand and model

I picture would help, but you will need ten posts before you can post one.
you can however place a picture in your album, then we can post it for you.

Barry
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Old 10-01-21, 09:21 AM
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Kapusta
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What front/rear gear combination are you in when this happens?
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Old 10-01-21, 09:36 AM
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Cm69.gb
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Thanks for the replies. I have created an album with the photos in
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Old 10-01-21, 09:46 AM
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Old 10-01-21, 01:22 PM
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Pic's

Picture Assist...




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Old 10-01-21, 01:27 PM
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It looks like you cleaned the chain too long (pun intended)

I'd check the chain length. Yes I read that it's the same chain, but was it the correct length to begin with?
It also appears that the wheel is quite far forward in the dropout.
Are you sure the screw in the derailleur hanger is in the correct place. Was it maybe originally in the rearward of the two eyelets, thus allowing the wheel to be more rearward.


Last edited by Barry2; 10-01-21 at 01:31 PM.
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Old 10-01-21, 01:40 PM
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Pull the wheel further back and put the chain in a bigger chainring, just to see how the rear der behaves.
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Old 10-01-21, 11:44 PM
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1. Learn how to size a chain.
2. Never shift into the small chainring/small rear cog nor the big/big gear combinations.
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Old 10-02-21, 09:45 AM
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Ive sized the chain and it is fine. The wheel will not go any further back and the derailleur will not fit on any other way. On the larger rings it is fine, its just the smaller one where the derailleur overlaps
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Old 10-02-21, 10:29 AM
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Put the chain around the big chainring on the front and the smallest sprocket on the back. A line beteween the derailleur jockey wheels (guide pulley and tension pulley) should be at 90 degrees up from the floor. (straight up) Looks to me that the chain is too long. You may have to remove some links....................
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Old 10-02-21, 10:46 AM
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Originally Posted by Cm69.gb View Post
Ive sized the chain and it is fine. The wheel will not go any further back and the derailleur will not fit on any other way. On the larger rings it is fine, its just the smaller one where the derailleur overlaps
Upload a picture of the chain on the large cog and on the large chainring. Then we will be able to tell if the chain is too long
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Old 10-02-21, 11:37 AM
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Ive added 2 more photos to my album. One with the small rear cog and large front cog and one with large front and rear cogs .

the problem is when I go small front and rear cogs
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Old 10-02-21, 12:17 PM
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Looks very much as if your chain is too long, but it is difficult to tell due to the angle from which the photos were taken.
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Old 10-02-21, 01:36 PM
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I will try and remove some links and see what happens
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Old 10-03-21, 04:06 PM
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If you sized the chain correctly, removing links is a very bad idea.
You can break the derailleur.
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Old 10-03-21, 05:07 PM
  #18  
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Well I removed a couple of links and it seems to have done the trick, now works fine. Ive never sized a chain before so hopefully I got the sizing wrong when I measured it!! Thanks everyone
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Old 10-04-21, 04:15 PM
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Read up on how to correctly size the chain. There are a couple of methods but the end result is to make sure the derailleur can stretch far enough to allow the large/large combination. With the tight spread of the 6-speed freeewheel you have, there's no way you're pushing the limits of that derailleur. Not even close.
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Old 10-05-21, 12:32 PM
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If the gearing is outside the capacity of the derailleur, the chain will have to be either too long or too short (or both). Some will do it anyway and just avoid the big/big and small/small combinations, but it just takes one lapse in attention to destroy the derailleur in that case.
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