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Discussion Starter · #1 ·
Hi everyone,

I'm currently facing a strange problem with a DA rear mech. Let's sum-up the situation :

The bike is fully equipped with DA7800, it's been in use for 3 years now and it's ridden all the year (between 8k and 9k kms/year) in all weathers.
This summer it was ridden with the hanger plate bent for many kms (may be 2000 km). We even bent it twice and we only had one hanger in reserve. We were racing in the French Alps and it was impossible to get a replacement. Ultra light stuff but not really reliable at the end...

Now the problem : the hanger was changed, I changed the pulleys (the Centeron G pulley was completely worn), it improved the precision but the derailleur is still unable to make it till the smallest cog. I also put plenty of WD40 inside the parallelogram but still no luck. It looks like this mech became a lazy boy after 3 years :rolleyes:

Only options I saw now are :

#1) Find a washer that will stand between the hanger and the derailleur to increase the overhang. I think it's not perfect because it will increase force on the hanger.

#2) Change the mech and get a new one : may be a Tiagra or an Ultegra to finish the bike. In the summer a new LOOK 695 will arrive ;-)

#3) Any other clever idea that someone would give me to solve this problem :)

Best regards,

Chris
 

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I know this is probably a stupid question but did you adjust the high-limit screw?

Did you test the derailleur without the cable attached? I've had cable/shifter issues that prevented the derailleur from going to the smallest cog. By testing it with no cable attached you rule those out.
 

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'brifter' is f'ing stupid
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check this too. if the washer w/ the tooth that clamps the cable is in the wrong orientation, the tooth gets in the way of the derailleur moving as far as it needs to. it's in the proper orientation in the photo(sorry for the crap dark photo) but if the tooth is 180° from this you'll have problems. it happens all the time and is obviously easy to check.
 

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Discussion Starter · #4 ·
I know this is probably a stupid question but did you adjust the high-limit screw?

Did you test the derailleur without the cable attached? I've had cable/shifter issues that prevented the derailleur from going to the smallest cog. By testing it with no cable attached you rule those out.
I've done both tests without any luck.
 

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Discussion Starter · #5 ·
check this too. if the washer w/ the tooth that clamps the cable is in the wrong orientation, the tooth gets in the way of the derailleur moving as far as it needs to. it's in the proper orientation in the photo(sorry for the crap dark photo) but if the tooth is 180° from this you'll have problems. it happens all the time and is obviously easy to check.
Good advice, I'll do the check asap.
 

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'brifter' is f'ing stupid
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ok...
so it did work previously, correct?
what's changed since it worked? bent hanger? pulley was worn, you changed it. you've undone the cable and made sure the high limit is loose enough for the derailleur to move, have you pulled on it to make sure? can you force it into high gear? the cable anchor bolt washer is in the proper position so the 'tooth' isn't stopping the parallelogram from moving?
i can't believe that the derailleur is worn out after 3 years and at most 30,000km. it should last that long. try setting it up from the beginning w/ the cable undone and make sure the limit screw is completely loose. if it doesn't work, i'm at a loss.
 

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'brifter' is f'ing stupid
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Check to see if the cable is frayed inside the shifter. I've had the same problem and that was the cause.
good idea. a badly frayed cable could stop the derailleur from pulling all the way down. another clue would be difficulty in getting the shifting adjusted...if it's been inconsistent, check the cable where it goes through the shifter.
very easy check if you've got slotted housing stops on the frame. put the bike in a work stand, shift to the small(est) cog you can. pedal the bike and push the derailleur to the large cog by hand. stop pedalling, leave the derailleur where it is. this will create a bunch of slack in the cable allowing you to remove the housing from the stop creating even more slack. pull the housing away from the shifter and while pulling the brake lever push the cable head out of the installation hole. if it's frayed, it will happen right at the end.
 

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rebounder
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you can always put a washer between the derailleur and the hanger, which will move it out another ~millimeter. plenty of threads for that. also make sure your cassette is tight.
 

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Discussion Starter · #10 ·
check this too. if the washer w/ the tooth that clamps the cable is in the wrong orientation, the tooth gets in the way of the derailleur moving as far as it needs to. it's in the proper orientation in the photo(sorry for the crap dark photo) but if the tooth is 180° from this you'll have problems. it happens all the time and is obviously easy to check.
Hi,

You gave me the solution. The washer with the clamp had a wrong orientation blocking the movement of the derailleur while it was moving to the smallest cog.

I made this mistake during the summer while changing the hanger. As everything was bent, I put this on the hanger and/or the pulleys.

I work on bike for years, but when you're in a hurry it's always the moment when you make mistakes.

Thanks to everyone for their help.

Best regards,
Chris
 

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Discussion Starter · #11 ·
The shifting was poor and I changed all the cables for that reason too.
Usually I change the cables every year. This year the cables weren't also in good shape.
This summer I raced every weekend and sometimes twice during the same WE so didn't had much time to take care of the bike. I know it will shorten the life of the components... but the race fever is too strong ;-)
 

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coaster
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Just yesterday at work I had a customer's bike doing this. It worked fine in every gear till shifting from 9 to 10 and the cable would go slack but the derailleur wouldn't move. I lubed all the pivots and cable/housing assuming friction/weak spring. If you pushed it over to 10 you could feel a distinct notch that you had to push through. I noticed some minor scuffing near one of the parallelogram pivots and found that pivot had been pinched slightly and the edge of the material bent so it contacted only during this last gear change. I used a hammer and thin screwdriver to pry open the pivot a little and get it working till he can afford a new Dura-ace derailleur.
 
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