5

Last week I realized that when I am on the big ring, crank arm touches front derailleur slightly. If I try to fix that with limit screw, then chain does the same (if I am on rear smallest gear). So it seems that there is not enough space between chain and crank arm for my front derailleur and I can't understand why.

My front derailleur is 1.5-2mm above from big ring and it is quite parallel to it. There is no bent or damage on front derailleur.

My components are;

  • Ultegra r8000 front and rear derailleur
  • Cassette 11-32T (shimano 105)
  • Ultegra chain
  • Ultegra r8000 crank set (52-36)
  • Bike is Canyon Endurace Al (components were ultegra 6800 few months ago)

So if you have any idea about how to fix it or what is the problem here I would like to learn.

By the way I have right arm only Stages Gen 3 power meter on crankset, but it seems irrelevant to me.

enter image description here enter image description here enter image description here enter image description here

FD out most FD outmost 2 Best adjustment possible

Improve this question
7
  • 1
    Either the derailer has gotten twisted on the downtube or the crank arm is bent.
    – Daniel R Hicks
    Mar 30, 2020 at 14:34
  • 2
    (Another possibility is that the horizontal bottom bracket adjustment has crept to the left.)
    – Daniel R Hicks
    Mar 30, 2020 at 14:58
  • How can I understand those things? crank arm is brand new, and very smooth, I dont think it is bent. I would like to learn if there is a way to understand if my horizontal bracket adjustment is correct or not.
    – Ruqki
    Mar 30, 2020 at 15:07
  • 2
    Current generation Shimano cranks are hollow, but they are also very massive. It's difficult to conceive of how one could bend the crank without creating some sort of visible damage. There's also not really a way to adjust the crank's lateral position. So, if the OP had properly adjusted their front derailleur's limit stops, this is very puzzling. I agree that the FD's mount being bent is possible. Far less likely, it seems possible that the entire frame could somehow be out of spec (e.g. they welded the BB asymmetrically and didn't notice this in quality control).
    – Weiwen Ng
    Mar 30, 2020 at 15:34
  • 2
    Could we have a picture of the FD and the ring, down the seat tube with the chain on big ring/small sprocket and the FD as far out as possible?
    – Carel
    Mar 30, 2020 at 18:20

2 Answers 2

Reset to default
1

I have a similar issue with my Shimano 5700 50-34 crankset and band-on derailleur, see telltale scratches in photo below from before I noticed and solved the problem. I don't know the provenance of my derailleur, it came second hand with the frame years ago, so I'm not sure why it should happen, but can share what I did.

Normal adjustments of the front derailleur weren't helping; with the derailleur aligned straight ahead, the outer plate would always catch the crank. If the high limit was tight enough to prevent this contact, it was too tight to allow the derailleur movement to the big ring.

So I struck a balance between high limit position and derailleur alignment. The tail of the derailleur is tucked just slightly inboard than I would normally align the FD, while the high limit is set so that the outer plate just doesn't contact the crank. I worked iteratively, angling the derailleur slightly, then checking the cable tension and the high limit vs rubbing the crank, then starting all over again if it wasn't right (patience). This was a few years ago and the derailleur operates fine in either direction, it is only skewed inboard a little bit.

Hopefully you can set up your derailleur with a little care and a little creativity to try something similar. Remember to have the rear derailleur set up correctly (limits included) before working on the front. Yours would be slightly more involved than mine because you have the newer design with the support screw and is a braze on. Then again, using the support screw to your advantage might allow you to be pretty precise in your adjustments.

enter image description here

No cables on the bike at the mo unfortunately, but you might see how the alignment is just slightly skewed in this photo - it is subtle!

enter image description here

Improve this answer
2
  • 1
    Your answer has solved my problem properly. Support screw let me adjust my FD properly, now there is enough space for both chain and crank clearance. Thank you.
    – Ruqki
    Apr 9, 2020 at 7:55
  • Hooray, well done, thanks for lettiing me know
    – Swifty
    Apr 9, 2020 at 8:00
2

Pic 1 shows that the outside plate of the FD is unnecessarily far out. It should just be a hair away from the chain when in big front and rear small. You'll have to adjust the limit screw quarter turn by quarter turn, so that the chain climbs on the big ring and does not rub against the outer plate. Also the outer plate should be parallel to the big ring.

On some bikes this adjustment can be a fiddly process requiring lots of patience. Also on YouTube check the videos from several pages like GCN or Park Tool.

Improve this answer
3
  • Actually picture 1 is a litte deceptive to understand position of chain. Picture 2 and 1 are same for chain perspective, it actualy touches to the chain. Picture 1 shows how close my crank arm to the derailleur, and 2 shows the chain without changing anything other than position of crank arm for better view of chain rubbing.
    – Ruqki
    Mar 30, 2020 at 15:02
  • Does the chainring remain in the same plane and not have a sideways motion when looking from the top like a wheel out of true, in other words,. does it stay at the same distance from the seat tube
    – Carel
    Mar 30, 2020 at 18:16
  • I just checked it and it seems that rotational movement of chainring is quite stable and it stays at the same distance from seat tube all the time.
    – Ruqki
    Mar 31, 2020 at 7:10

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.