Rear derailleur problem
Hello everyone
I hope someone can advise me with this problem I have. The groupset on one of my bikes is 10 speed Shimano 7800 Dura Ace. I've installed a new cable to the rear derailleur as the one that was replaced was quite old. The new cable runs very smoothly through all the cable housings without any issues at all.
I've spent a fair amount of time and frustration trying to adjust the rear derailleur so that it shifts ok. I've tried adjusting the high, low and B-tension screws on the derailleur, whilst also for good measure following a copy of the shimano technical service instructions for the 7800 rear derailleur. But so far with no luck. I've removed, cleaned and then refitted the rear derailleur, checked to see if the derailleur cage is bent and it's ok. I've changed the cassette on the rear wheel to see if that helped, but it didn't. The chain shifts up and down most of the cassette ok, but will not shift onto the smallest sproket at all. It struggles to shift onto the second smallest sprocket when you shift the chain down the cassette.
What I do notice with the chain though, is that there is a fair amount of chain slack regardless of how much adjusting of the rear derailleur you do. This occurs when the chain is on the small front chainring and you shift the chain onto the smaller sprockets of the cassette. The derailleur doesn't seem to want to pull the chain taut when it's in its relaxed position. You can see the chain sagging down towards the gound. I did think the chain was worn but it's ok as I checked it with a chain wear tool. The chain was sagging before I replaced the cable, as I thought perhaps the cable run was sticking a little but it wasn't. So I'm thinking perhaps the rear deailleur is knackered and it needs to be replaced.
So after a bit of a long explanation, could I replace the old 10 speed 7800 rear deailleur and use an 11 speed one instead? The reason for an 11 speed one, is the option of fitting something like a 32 or 34 tooth cassette which I would like to do.
I hope someone can advise me with this problem I have. The groupset on one of my bikes is 10 speed Shimano 7800 Dura Ace. I've installed a new cable to the rear derailleur as the one that was replaced was quite old. The new cable runs very smoothly through all the cable housings without any issues at all.
I've spent a fair amount of time and frustration trying to adjust the rear derailleur so that it shifts ok. I've tried adjusting the high, low and B-tension screws on the derailleur, whilst also for good measure following a copy of the shimano technical service instructions for the 7800 rear derailleur. But so far with no luck. I've removed, cleaned and then refitted the rear derailleur, checked to see if the derailleur cage is bent and it's ok. I've changed the cassette on the rear wheel to see if that helped, but it didn't. The chain shifts up and down most of the cassette ok, but will not shift onto the smallest sproket at all. It struggles to shift onto the second smallest sprocket when you shift the chain down the cassette.
What I do notice with the chain though, is that there is a fair amount of chain slack regardless of how much adjusting of the rear derailleur you do. This occurs when the chain is on the small front chainring and you shift the chain onto the smaller sprockets of the cassette. The derailleur doesn't seem to want to pull the chain taut when it's in its relaxed position. You can see the chain sagging down towards the gound. I did think the chain was worn but it's ok as I checked it with a chain wear tool. The chain was sagging before I replaced the cable, as I thought perhaps the cable run was sticking a little but it wasn't. So I'm thinking perhaps the rear deailleur is knackered and it needs to be replaced.
So after a bit of a long explanation, could I replace the old 10 speed 7800 rear deailleur and use an 11 speed one instead? The reason for an 11 speed one, is the option of fitting something like a 32 or 34 tooth cassette which I would like to do.
2004 Trek 5500 OCLV
2014 Cervelo R3 Black/Blue
2018 Cervelo R3 Disc Navy/Red
2018 Trek Domane SL 5 Disc Grey
2020 Trek Domane SL 5 Disc Matte Navy
2014 Cervelo R3 Black/Blue
2018 Cervelo R3 Disc Navy/Red
2018 Trek Domane SL 5 Disc Grey
2020 Trek Domane SL 5 Disc Matte Navy
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Comments
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Most likely you've installed it wrong.
Pictures help.I don't do smileys.
There is no secret ingredient - Kung Fu Panda
London Calling on Facebook
Parktools0 -
I had an issue similar to this, couldn't figure out the problem, eventually I stripped down the upper knuckle. It was somewhat rusty. I cleaned it and applied WD40 and then some oil and reassembled, a bit awkward to get the spring back correctly but not too difficult either.
It worked perfectly after this0 -
The only compatible rear derailleur in Shimano's current line up is the Sora.
Shimano changed pull ratio for 11 speed and the change has trickled down to tiagra.
On the up side they are compatible with 32/34 teeth cassettes.0 -
Thanks for your comments. Thought I'd post some pictures as recommended by cooldad. The chain shows what is occuring with the chain sagging and it was sagging in the same way before I tried to sort it.
In the picture below I'm pushing the cage rearwards which stops the chain from sagging.
When I release my finger the chain sags again.
I'm thinking now about doing what OnTheRopes mentioned and taking it apart to clean and lub the inner mechanism.2004 Trek 5500 OCLV
2014 Cervelo R3 Black/Blue
2018 Cervelo R3 Disc Navy/Red
2018 Trek Domane SL 5 Disc Grey
2020 Trek Domane SL 5 Disc Matte Navy0 -
Pivot or the spring in the rear derailleur stiff or bust.0
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Looks to me like the b screw isn't up against the stop on the hanger. But can't see clearly.
Looks like it's just dangling.I don't do smileys.
There is no secret ingredient - Kung Fu Panda
London Calling on Facebook
Parktools0 -
Looks like the pivots need proper servicing. You can find You Tube demos for how to do this.....FFS! Harden up and grow a pair
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If it was working before changing cables, there's no reason it's suddenly not working except for setup.I don't do smileys.
There is no secret ingredient - Kung Fu Panda
London Calling on Facebook
Parktools0 -
My rear mech on my winter bike was working fine the last time I rode it. However despite having cleaned it and lubed it when I rode it 2 weeks later the pivot was completely immovable. I wasn’t too heartbroken as it was about 15 years old.0
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Top pivot can't be right. Strip and clean. You can reassemble wrong though and it won't work properly.http://www.thecycleclinic.co.uk -wheel building and other stuff.0
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Managed to sort the problem, I can't believe I didn't notice it earlier. When I stood back and looked at my other bikes I suddenly realised that the derailleur wasn't folding in on itself. The jockey cage should have sprung back into the mechanism, but it was jammed. The parts had seized up. So I removed the derailleur from the bike and took the jockey cage off the mechanism. All the parts were rusty on the insde as shown below.
I've cleaned all the parts up and lubricated them as well, reassembled the derailleur and refitted it. It's all adjusted and shifting quite nicely now. I can now see why adjusting all the screws at the start had no effect whatsoever when I tried intially to sort it out. Didn't take long to set the derailleur up using the screws on it when it was refitted to the bike.
Thanks for all the further comments and advice.
2004 Trek 5500 OCLV
2014 Cervelo R3 Black/Blue
2018 Cervelo R3 Disc Navy/Red
2018 Trek Domane SL 5 Disc Grey
2020 Trek Domane SL 5 Disc Matte Navy0 -
That does look a bit better...I don't do smileys.
There is no secret ingredient - Kung Fu Panda
London Calling on Facebook
Parktools0 -
nice job, this is not unusual if you've ridden on salty roads.0
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Good job! The upper pivot will probably be in a similar condition and can also be stripped. Also re-lube with grease (rather than oil) giving the springs a good coat too.
Park tools has a comprehensive guide http://www.parktool.com/blog/repair-help/rear-derailleur-overhaul.0 -
Thanks jermas for the comment and the link, that's really useful. I did look at the top pivot and thought about stripping it too, but it was moving very freely without any problems so decided to leave it alone.
I did as you've commented though and smeared all the components with grease when I had it disassembled, as I thought it would be better instead of some oil. I was surprised though to see the rust on the components, as I thought there would be some grease or something in there as a protective coating.
I did get a feeling of satisfaction from getting it back to a serviceable condition and saving myself the pain and expense of sourcing and purchasing a replacement. 2004 Trek 5500 OCLV
2014 Cervelo R3 Black/Blue
2018 Cervelo R3 Disc Navy/Red
2018 Trek Domane SL 5 Disc Grey
2020 Trek Domane SL 5 Disc Matte Navy0 -
Clu wrote:Thanks jermas for the comment and the link, that's really useful. I did look at the top pivot and thought about stripping it too, but it was moving very freely without any problems so decided to leave it alone.
I did as you've commented though and smeared all the components with grease when I had it disassembled, as I thought it would be better instead of some oil. I was surprised though to see the rust on the components, as I thought there would be some grease or something in there as a protective coating.
I did get a feeling of satisfaction from getting it back to a serviceable condition and saving myself the pain and expense of sourcing and purchasing a replacement.
Ha its great fun getting stuck in and fixing stuff.. Nicely done
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