Wrench question: RD movement when shifting from big ring to small ring

May 23, 17 12:58

Post #1 of 20 (1780 views)

This may be somewhat difficult to explain, but when riding on the trainer I notice when I shift from 53 to 39 my RD upshifts a hair (faster gear). It does not make a complete shift, but the RD moves enough (maybe 1/3 shift) that I get clickedy in the chain. A quick downshift or upshift fixes the issue. I'm not sure what could cause this as I'm not touching the rear shifter so indexing shouldn't change during the shift. I did just replace cables about a month ago. Everything seems in order, spotless, shifting is generally perfect but may require a barrel tweak now and then.

I'm using all factory DA9000 mech parts (ultegra cassette). 53-39 with 11-28. Original RD with maybe 20,000 miles. Original FD, all other parts are newish or recently replaced with new.

Thanks for any tips.

24 Hour World TT Champs-American record holder
Fat Bike Worlds - Race Director
Insta: chris.s.apex

Re: Wrench question: RD movement when shifting from big ring to small ring [cmscat50] [ In reply to ]

May 23, 17 13:16

Post #2 of 20 (1770 views)

Buy a new rear derailleur.

Re: Wrench question: RD movement when shifting from big ring to small ring [cmscat50] [ In reply to ]

May 23, 17 13:29

Post #3 of 20 (1752 views)

cmscat50 wrote:

This may be somewhat difficult to explain, but when riding on the trainer I notice when I shift from 53 to 39 my RD upshifts a hair (faster gear). It does not make a complete shift, but the RD moves enough (maybe 1/3 shift) that I get clickedy in the chain. A quick downshift or upshift fixes the issue.

That sounds really strange... when the RD moves toward an easier gear (cog), it is from an increase in tension in the RD cable. If anything, I would expect it to move toward a harder gear as something causes slack or jiggles the system.

Here's my quick mechanical breakdown of the dynamics. When you go from big to small up front, that increases chain slack. When that happens, the cage spring absorbs the slack by pulling the cage rearward. So, if the derailleur hanger is bent, the cage shift could cause an effective lateral shift in the cog closest to the cassette. This does not explain why an RD upshift/downshift fixes it.

Re: Wrench question: RD movement when shifting from big ring to small ring [exxxviii] [ In reply to ]

May 23, 17 13:35

Post #4 of 20 (1746 views)

I'm sorry if I was unclear. It shifts a hair toward the harder gear. Hanger is perfectly straight. I just checked it.

24 Hour World TT Champs-American record holder
Fat Bike Worlds - Race Director
Insta: chris.s.apex

Re: Wrench question: RD movement when shifting from big ring to small ring [cmscat50] [ In reply to ]

May 23, 17 13:39

Post #5 of 20 (1743 views)

Doh, OK, that totally makes sense. What is happening is that you have a little binding in your RD cable or the RD shifter. When you shift the RD from a harder (smaller/faster) cog to an easier cog, the shifter is designed to go a little past the click and then settle back at the click spot. But, if there is a little friction in the cables or the shifter's internal mechanism is not smooth, then it can stick at that over-shift point rather than settling back at the click spot. The jolt of the FD shift is then triggering the RD/cable/shifter to re-settle at its proper spot.

Re: Wrench question: RD movement when shifting from big ring to small ring [exxxviii] [ In reply to ]

May 23, 17 13:43

Post #6 of 20 (1734 views)

OK thanks. As far as I can tell cables are butter smooth. RD is cleaned very well. I guess I could do it again, but it's never been dirty.

As the first response says maybe it's time for a new RD. This one has a ton of clicks in it!

24 Hour World TT Champs-American record holder
Fat Bike Worlds - Race Director
Insta: chris.s.apex

Re: Wrench question: RD movement when shifting from big ring to small ring [cmscat50] [ In reply to ]

May 23, 17 13:48

Post #7 of 20 (1726 views)

Possibly. But if you you are first noticing it after the cable change, the odds are high it is the cable or shifter.

Re: Wrench question: RD movement when shifting from big ring to small ring [exxxviii] [ In reply to ]

May 23, 17 13:51

Post #8 of 20 (1719 views)

I hope not. When I re-cabled I ran the cable through the housing to assure everything was buttery smooth. It was. Not saying the shifter couldn't be an issue as that's got a ton of clicks in it as well.

24 Hour World TT Champs-American record holder
Fat Bike Worlds - Race Director
Insta: chris.s.apex

Re: Wrench question: RD movement when shifting from big ring to small ring [jimatbeyond] [ In reply to ]

Henrik Noerskov

May 23, 17 14:04

Post #9 of 20 (1706 views)

Infernal cabling? Sounds a lot like cables crossed inside the frame.

As you slacken the fd cable the rd cable would then also loosen which would cause the rear derailleur to crawl ever so slightly outwards. If this is the problem you should also have problems adjusting your rear. When adjusted perfect on the small ring you will have problems going to harder gears on the rear while in the big ring. When adjusted perfect on the big ring you will have problems going to smaller gears when in the small ring.

Disclaimer: I have made a living in bike shops for more than 2 decades, so according to most people on this forum am not at all trust worthy

Re: Wrench question: RD movement when shifting from big ring to small ring [Henrik Noerskov] [ In reply to ]

May 23, 17 14:10

Post #10 of 20 (1701 views)

Yes sir. Internal routing. So what's the best method to guarantee cables aren't crossed? You can't see anything in there and I don't doubt you could be right!

24 Hour World TT Champs-American record holder
Fat Bike Worlds - Race Director
Insta: chris.s.apex

Re: Wrench question: RD movement when shifting from big ring to small ring [cmscat50] [ In reply to ]

PoorLBSEmployee

May 23, 17 14:18

Post #11 of 20 (1689 views)

If you have an internally routed frame, you can cross the shift cables inside the frame and this happens sometimes.

Re: Wrench question: RD movement when shifting from big ring to small ring [PoorLBSEmployee] [ In reply to ]

May 23, 17 14:19

Post #12 of 20 (1684 views)

How do I assure they are not crossed? It's impossible to see in there? Any tricks?

24 Hour World TT Champs-American record holder
Fat Bike Worlds - Race Director
Insta: chris.s.apex

Re: Wrench question: RD movement when shifting from big ring to small ring [cmscat50] [ In reply to ]

May 23, 17 14:22

Post #13 of 20 (1677 views)

Most frames with internal cable routing have separate tubes for each cable so there is no chance of touching each other.

Re: Wrench question: RD movement when shifting from big ring to small ring [jimatbeyond] [ In reply to ]

May 23, 17 14:25

Post #14 of 20 (1672 views)

This a 2014 Madone. It's got a fitting on the top end of the downtube. It has a bottom bracket cable guide on the bottom. I'm pretty certain it's just dead air in between. As in the cables could just wind around each other when fishing through....lol. Maybe I'm giving away my lack of mech skills here, but honestly I'm a pretty handy guy!!!

24 Hour World TT Champs-American record holder
Fat Bike Worlds - Race Director
Insta: chris.s.apex

Re: Wrench question: RD movement when shifting from big ring to small ring [cmscat50] [ In reply to ]

PoorLBSEmployee

May 23, 17 14:25

Post #15 of 20 (1672 views)

If they're cut and crimped, you're basically out of luck, and get to redo the cabling. You can try to undo the bolts and pull one cable and try and feel for movement in the other, but it can be hard to tell for sure.

When you set up the cables, you want to pull them tight out of the bottom before you install the guide. Pull them to their respective sides, making sure they're straight, then put the guide on and continue.

Re: Wrench question: RD movement when shifting from big ring to small ring [cmscat50] [ In reply to ]

Henrik Noerskov

May 23, 17 14:28

Post #16 of 20 (1671 views)

Have the wires hang loose at the bottom bracket. Hold one wire lightly with one hand, while pulling on the other in zaps. if you feel the one you are holding moving they are crossed. Then you twist them one rotation clockwise. If it gets better do on more if it gets worse you go counter clockwise instead. It can sometimes be a bit hard to tell, so take your time until you feel no movement, in the wire you are holding while pulling on the other.

Disclaimer: I have made a living in bike shops for more than 2 decades, so according to most people on this forum am not at all trust worthy

Re: Wrench question: RD movement when shifting from big ring to small ring [jimatbeyond] [ In reply to ]

Henrik Noerskov

May 23, 17 14:34

Post #17 of 20 (1664 views)

I am pretty sure i have seen more frames without separate tubes than i have seen with them. But in any case i am sure we can agree that frames do exist without them....

Disclaimer: I have made a living in bike shops for more than 2 decades, so according to most people on this forum am not at all trust worthy

Re: Wrench question: RD movement when shifting from big ring to small ring [cmscat50] [ In reply to ]

May 23, 17 19:36

Post #18 of 20 (1611 views)

cmscat50 wrote:

This a 2014 Madone. It's got a fitting on the top end of the downtube. It has a bottom bracket cable guide on the bottom. I'm pretty certain it's just dead air in between

Correct. There is nothing in your down tube to stop the cables from wrapping around each other.

Easiest way to get them to run straight is to run a bit of liner up the down tube. They are a bit stiffer than a cable so should run straight. 9 times out of 10 that works.

Failing that remove your cranks and BB and run a piece of housing up trough the BB and use that to chase the cable back down. You'll only need to do it for one of the cables and I prefer to chase the FD cable. Leave your RD cable installed and shift down a few gears so that there is tension on the cable, helping it stay straight. Then chase a length of housing up through the BB and use that to feed the FD shift cable back down. Hey presto, no tangles.

Also check your chain length and B-Tension.

Re: Wrench question: RD movement when shifting from big ring to small ring [jimatbeyond] [ In reply to ]

May 24, 17 4:04

Post #19 of 20 (1542 views)

jimatbeyond wrote:

Most frames with internal cable routing have separate tubes for each cable so there is no chance of touching each other.

Very rare for bikes to have internal separation or any type of guides internally.

The best way to re-cable is to push some of the teflon liner from a gear casing up the old cable and then remove the old cable.
New cable is simply run down the teflon tube and then the tube removed.
It is handy to tape the teflon tube to the outside of the frame at both ends as soon as you can to stop it being dropped inside by accident.

That is how all new bike frames come as standard.
And yes you have most certainly crossed them to cause your symptoms.

Re: Wrench question: RD movement when shifting from big ring to small ring [Henrik Noerskov] [ In reply to ]

May 26, 17 14:07

Post #20 of 20 (1445 views)

Wanted to update this so others are more careful. As hard as it is to see in the frame the cables definitely appeared to be crossed!

We unhooked both cables at the derailleurs. We were able to fish the entire FD cable and cable end through the BB cable guide. Doing that we were also able to slacken the RD cable enough to loosen the BB cable guide and wrap the FD cable around the RD cable using a bore scope (yes). So we unwrapped it correctly and re-installed. It was only crossed once.

The difference is not huge, but it's enough that I notice it. Should be good to go now with no micro shifting. Thanks for the tips guys!!!!!!!!!!!!

24 Hour World TT Champs-American record holder
Fat Bike Worlds - Race Director
Insta: chris.s.apex

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