Dura Ace Rear Derailleur Chain Path

bsharp77

Good morning guys,

I apologise in advance for this being probably the simplest of questions for most of you.....

Ive been getting a bit of noise, especially when in the big ring at the front, so i thought id give the weekend bike a real good clean yesterday and investigate - the sound appears to be coming from the bottom cog of the rear derailleur, and after looking again im thinking the chain path is not correct:



Am I right in thinking the chain should run directly on the bottom cog and not around the outside of that holder??
I have ultegra on another bike and this is what made me wonder, as it is in direct contact with that cog (although the holder is slightly different which made me question maybe this was just a dura ace thing).

I haven't changed the chain since I got the bike, so I assume this is the way it would have came from the shop - surely theres no way it could have slipped or moved out there by accident?....I cant see any way to put it back in without breaking the chain.

Apologies for the ignorance on this, I really am useless at anything mechanical....lucky we have these forums to turn to for help!

ElectronShepherd

That's definitely wrong - the chain should "hug" the jockey wheel all the way round.

sungod

^^^this

the path over the upper wheel also looks wrong - the *only* parts of the rear mech that the chain should touch are the jockey wheels

it's possible the chain running over parts it should not touch may have damaged the rear mech

if it's representative of the expertise of the person who assembled the bike, i'd have a very careful check of everything else to make sure there're no other nasty surprises

bsharp77

Thanks for the very quick and helpful responses guys - my worst fears are confirmed!
I refused to believe it could have been setup so wrong, as it was bought over 6 months ago from a very reputable retailer in SW London who deal in a lot of top quality bikes.
Looks like ill have to drop it down to my trusty LBS who will be able to assess the full extent of the ineptitude.

Thanks a lot for your help guys, much appreciated.

mike1-2

Pretty easy way of sorting that without breaking the chain or taking it into the shop.

The bottom wheel is held in place by one allan key bolt, undo this and remove the wheel, slide the chain underneath the small guide it is currently sat on and refit the bottom wheel as it came off, job done.

bsharp77

The only thing that is weird about this is that the bike has been running silent and smooth for months on end - racking up over 6000 miles with no noises or problems (I guess thats why I never noticed or investigated before now).

Its a very strange one and im absolutely gobsmacked that such a fundamental error was made on such an expensive bike....goes to show the importance of having a mechanic or lbs you can trust (and of course all the helpful advice on here!)

mike1-2

It happens, it shouldn't of caused any issues, and at least your bottom jockey wheel will be in top condition!

bsharp77

Good morning Mike, thanks for the reply - please excuse my ignorance, but removing the jockey wheel wont help me slide the chain to the other side of the little roller (which the chain is running around on the extreme left hand side of the rear derailleur).
Its that little roller which is stopping the chain from resting on the jockey wheel on the left and I can see no way to get the chain to the inside, without breaking it and threading it through the correct path.

xscreamsuk

6000 miles on one chain? Kill two birds with one stone,

drlodge

bsharp77 wrote:

The only thing that is weird about this is that the bike has been running silent and smooth for months on end - racking up over 6000 miles with no noises or problems (I guess thats why I never noticed or investigated before now).

I find it hard to believe the chain has done 6,000 miles especially with it like as shown in the photo. It would surely have worn through the RD cage.

sungod

yep

i'd be wondering who the practical joker is who just did it

bsharp77

Thats whats really bothering me too....which is why im wondering is there any way this could have possibly happened since I got the bike. The only maintenance i've ever done is to clean, and of course change the odd puncture....and its not been to the LBS for a service yet.
(Just had a quick check on strava - sorry its only 2000 miles (I have another bike which accounts for the rest of the mileage!), but still, as you say, surely enough to cause problems before now.)
I also checked the chain with the park tool yesterday and its still well within its lifespan.

Bozman

This has got to be a wind up

ic.

drlodge wrote:

bsharp77 wrote:

The only thing that is weird about this is that the bike has been running silent and smooth for months on end - racking up over 6000 miles with no noises or problems (I guess thats why I never noticed or investigated before now).

I find it hard to believe the chain has done 6,000 miles especially with it like as shown in the photo. It would surely have worn through the RD cage.

Quite

bsharp77

Sorry IC, after checking its only 2000 miles, but still....quite a lot for a chain thats not running where it should.

Bozman - not a wind up i'm afraid - makes me even more angry knowing that the bike has been setup so badly in the first place!

mike1-2

bsharp77 wrote:

Good morning Mike, thanks for the reply - please excuse my ignorance, but removing the jockey wheel wont help me slide the chain to the other side of the little roller (which the chain is running around on the extreme left hand side of the rear derailleur).
Its that little roller which is stopping the chain from resting on the jockey wheel on the left and I can see no way to get the chain to the inside, without breaking it and threading it through the correct path.

Nah, because the bolt that holds the jockey wheel in also holds the two sides of the cage together also, whip that out and you'll be able to get a gap big enough to slide the chain in. Give it a go, you'll be surprised.

bsharp77

Ah thanks a lot Mike, ill give that a try this evening and see how I get on.....many thanks for all the helpful comments.

bsharp77

A huge thanks to everyone who gave help - special mention to Mike - as you suggested, I undone the allen key and was able to put the chain back in its proper place! Now running smooth as butter.

Thinking about it all the way home this evening, theres no way it was built like this. Thinking back, I do remember being out on a saturday run a few weeks ago and changing gears only to hear a horrendous clattering sound followed by what sounded like something falling off....!!
I forgot about it at the time as everything appeared ok....but perhaps somehow the chain managed to get out (it was a quite horrible sound). It seems the most plausible explanation, as I don't think the chain would have survived 2000 miles out there! (not to mention the fact I couldn't believe it was built like this on purpose, or the fact I never noticed it before now).

Either way, i'm all sorted again thanks to the kind support of everyone on here - apologies if it seemed like a wind up or a trivial matter - I am quite useless at the mechanical side of things, but determined to become more knowledgeable this winter season when the dark evenings arrive!

Thanks again.

mike1-2

Glad it helped, saved some cash and faffing with taking the chain off.

mamba80

bsharp77 wrote:

Thinking about it all the way home this evening, theres no way it was built like this. Thinking back, I do remember being out on a saturday run a few weeks ago and changing gears only to hear a horrendous clattering sound followed by what sounded like something falling off....!!
I forgot about it at the time as everything appeared ok....but perhaps somehow the chain managed to get out (it was a quite horrible sound). It seems the most plausible explanation, as I don't think the chain would have survived 2000 miles out there! (not to mention the fact I couldn't believe it was built like this on purpose, or the fact I never noticed it before now).

Either way, i'm all sorted again thanks to the kind support of everyone on here - apologies if it seemed like a wind up or a trivial matter - I am quite useless at the mechanical side of things, but determined to become more knowledgeable this winter season when the dark evenings arrive!.

I wouldn't bother

Old_Timer

Deleted content, not sure about this one, at all.

rolf_f

bsharp77 wrote:

I forgot about it at the time as everything appeared ok....but perhaps somehow the chain managed to get out (it was a quite horrible sound). It seems the most plausible explanation, as I don't think the chain would have survived 2000 miles out there! (not to mention the fact I couldn't believe it was built like this on purpose, or the fact I never noticed it before now).

That isn't actually a remotely plausible explanation! It's about as plausible as me outsprinting Andre Greipel. Infact, the only plausible explanation for what you described that I can think of is as sungod has already suggested - someone tampered with your bike.

ic.

bsharp77 wrote:

Thinking about it all the way home this evening, theres no way it was built like this. Thinking back, I do remember being out on a saturday run a few weeks ago and changing gears only to hear a horrendous clattering sound followed by what sounded like something falling off....!!
I forgot about it at the time as everything appeared ok....but perhaps somehow the chain managed to get out (it was a quite horrible sound). It seems the most plausible explanation, as I don't think the chain would have survived 2000 miles out there! (not to mention the fact I couldn't believe it was built like this on purpose, or the fact I never noticed it before now).

Given what you had to do to get the chain back to where it should be, do you really think this is possible? Did the noise, as horrible as it was, sound like a chain ripping through metal then firing up a magical blow torch/welding rig in order to repair the messed up metal on the mech cage so you wouldn't notice it's happened?

Either you've taken the chain off yourself then put it back incorrectly, or someone has done it for you. Not sure which I think more likely at this point

bsharp77

How would I know whats possible? Im a mechanical novice, thats the reason im on here in the first place...for some help....which I have got from some very courteous forum members.

But as usual on here some people have to go out of their way to make sure they get a dig in to make you feel stupid.

mamba80

Some support for you buddy!
the plates on my RD 7900 mech can be sprung apart and being CF they wouldnt bend or break very easily. the pin is only attached to the inside cage plate.... so it is feasible that a stone could have jammed in against the jockey wheel and forced the plate apart and the chain rode up and over the pin, using the stone as a jemmy.... its highly unlikely BUT not entirely impossible.
the scenario that some one did this as a practical joke seems improbable and the OP "seems" genuine in his denials that he may have done this himself and there is no way the alloy pin would have lasted 2k miles if it was from new.... so I maybe we should accept this on face value.
But tbh who really cares ?

Matthewfalle

I blame Wiggle.

bsharp77

Ha ha! Cheers Mamba, I guess we'll never get to the bottom of this one, but I can assure you its genuine - and to be fair, I can understand some of the scepticism...but it was the peculiar nature of the issue that made me post in the first place! As you say, the problem has been resolved thanks to some great help on here and the bike is running great - just back from a 50km loop to make sure its all ok. Thanks all.

rolf_f

bsharp77 wrote:

How would I know whats possible? Im a mechanical novice, thats the reason im on here in the first place...for some help....which I have got from some very courteous forum members.<br abp="877"><br abp="878">But as usual on here some people have to go out of their way to make sure they get a dig in to make you feel stupid.

Not sure anyone is having a dig. I certainly wasn't. It's great that you are up and running again but it is important to find out what happened if possible to avoid it happening again. If Mamba is correct then there is a simple solution - avoid Dura Ace rear mechs due to shockingly bad engineering! But I'd be still concerned that someone might be playing silly buggers with your bike. It does happen. Someone on here irrc had their headset loosened - obviously quite a dangerous thing to do.