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-   -   Chain keeps falling off brand new Kona Rove (Shimano Sora) (https://www.bikeforums.net/bicycle-mechanics/1202521-chain-keeps-falling-off-brand-new-kona-rove-shimano-sora.html)

NYNJrider 05-24-20 07:49 PM

Chain keeps falling off brand new Kona Rove (Shimano Sora)
 
chain keeps falling off when shifting from the small to big chainring and falls off on the crank side. i've also been having a lot of difficulty shifiting in general from big to small - i have to press the shifter multiple times, sometimes it wont shift unless i shift down almost all the way on the cassette, sometimes it doesn't shift at all.

i watched the Park Tools video.

it appears the FD is set properly in term of height and alignment.

i messed around with the limit screws as well, didn't seem to be much help.

any thoughts?

NYNJrider 05-24-20 07:51 PM

bunch of photos here:

https://imgur.com/a/aXbPIzV

Andrew R Stewart 05-24-20 09:05 PM

I suspect there may be a few different things going on. The big ring chain drop is often an adjustment issue. Ft der twist, height and outward limit. But the shift to the small ring can sometimes be technique. Why would a shift lever release to the small ring act any different after a few times? Because the rider is also changing their pedal pressures. The classic is an attempt to shift down to the small ring with no result (but grinding) because the chain is too taught, too much pedal pressure. Rider moves lever back to large ring to stop grinding and tries again. But now their cadence is slowing and to keep momentum they push harder on the pedals (after all the reason to down shift is usually because of a hill or headwind). Attempt two does no better with the slower cadence (and that the shift gate takes longer to align with the even more tensioned chain). At some point of repeating this the rider, whether knowingly or not. shifts when the chain is relaxed enough to allow the der's return spring to overcome the chain tension, and the chain gets moved over enough to cause a shift.

Of course other issues contribute to these things. Like a well worn chain that now has a lot of lateral flex. Or a messed up shifter that won't release or move up as it should. Then there's the cable routing thing about the anchor bolt and it's tab's guide stub. Any thought about this? Andy

Andrew R Stewart 05-24-20 09:06 PM

In should have asked if the purchased from shop can duplicate the problems on their test rides? Andy

Miele Man 05-24-20 09:26 PM

Overshifting to between the big chainring and crankarm can be cured usually be adjusting the high limit bolt on the front derailleur. If shifitng has changed only a short time after buying a new bike or any bike with cables and housings it could be that the cable housings are bedding in and becoming a bit shorted and thus the amount of cable is now slightly different but still enough to throw shifting off.

Cheers

oldbobcat 05-24-20 09:40 PM

If the cage angle is correct (outer plate parallel to the chain rings) and the cage height is correct (1-2mm above the tallest teeth on the big ring), the reason for overshifting the big ring is nearly always because the cage is pushing the chain too far. To remedy that, tighten release a smidge of tension on the cable and tighten the high limit screw a smidge. Ideally, when the chain is on small in back, big in front, it should clear the outer plat of the front derailleur by about a millimeter. The unit should "kiss" the limit screw just as maximum cable tension is reached. Too loose and you overshift. Too tight and there's too much cable tension to allow trim and downshifts, and eventually you'll break the shifter.

cpach 05-24-20 09:45 PM

https://www.parktool.com/blog/repair...eur-adjustment

Do every stop, beginning to end.

If your adjustment of the limits can be plausibly described as "messing around", then you really should just try again.

NYNJrider 05-28-20 06:13 PM


Originally Posted by cpach (Post 21495380)
https://www.parktool.com/blog/repair...eur-adjustment

Do every stop, beginning to end.

If your adjustment of the limits can be plausibly described as "messing around", then you really should just try again.

messing around in the sense that i'm a complete noob but following the Park Tools video.

to me, it appears the cage is angled correctly and at the right height (do my photos shed any light on this?).

i am thinking it MUST be the limits. the limit screw closest to the frame seems to be quite loose in that it appears less "screwed in" than the other. if i am understanding the Sora instruction manual correctly, the screw closest to the frame is the L and the screw closest to the crank is the H: https://si.shimano.com/pdfs/dm/DM-RBFD001-01-ENG.pdf

i turned both of these a bit. maybe 1 or 1.5 full rotations. strangely it certainly looks like the space between the the chain and the cage is more than 1mm even after a rotation. is it possible a few more rotations are needed?

ultimately, at this point, the chain still falls off towards the crank/pedal side and i'm still having occasional difficulty shifting from the large to small chainring.

NYNJrider 05-28-20 06:14 PM


Originally Posted by Andrew R Stewart (Post 21495333)
In should have asked if the purchased from shop can duplicate the problems on their test rides? Andy

i have yet to try them. i called and they told me there's at least a 10-day lag (due to COVID) and i should attempt to fix it myself.

TiHabanero 05-28-20 06:23 PM

Front derailleur adjustment is a bit of a black art. Same can be said when using a front derailleur. Shimano has tried a few things to eliminate the 6th sense needed to successfully adjust them, but up until the newest 8100 ft der, it has not helped much. I suggest getting someone with experience involved in this and learn from them.

Andrew R Stewart 05-28-20 08:39 PM

"i have yet to try them. i called and they told me there's at least a 10-day lag (due to COVID) and i should attempt to fix it myself." We're 20 days backlogged so I understand their situation. However we do try to accommodate our new bike customers best possible and rarely suggest they do their own repairs when the bike is still under a service warranty period.

"Front derailleur adjustment is a bit of a black art." Not sure i completely agree. However the variables with ft der adjustments are many and effect each other so i can understand why many feel this way. Perhaps it's more like playing chess. A good player understands the cause and effect of various moves better then novices do and can reach a final point faster, but can still not guaranty the outcome. Andy (reaching for a better metaphor)

cb400 05-28-20 09:18 PM

I think I spent about 4 hours figuring it out the first time I adjusted a triple derailleur. I then spent another 3 hours on the next triple. I'm a slow learner until I get it then I've really got it.

The park video should work for a double if you follow the steps and make sure you are turning the correct limit screw. It also seems like you are not considering the cable tension, which is equally important to all the other adjustments, especially on an indexing system.

woodcraft 05-28-20 10:06 PM

In the last batch of pics, with the chain is in the big ring, and likely in next to smallest cog,

the outside of the der. cage looks close to the chain at the front, but with a big gap at the back.

This could explain the issue, and rotating the der. so the outside of the cage is evenly close to the chain would help.

You can tell which limit screw is which because it is the one touching something when the der. is in or out.

Keep at it!

NYNJrider 05-29-20 05:46 AM

thanks all. im going to take another crack at it today. as an aside, how much should one be turning a limit screw? in the Park Tools video it seems he turns it very little, however is there a chance it might need a couple rotations or more to adjust?

my issue is complicated a bit by not having a stand - i feel that would help.

at any rate, i'll be sure to come back and post more pics if the issue remains.

alcjphil 05-29-20 05:50 AM


Originally Posted by NYNJrider (Post 21503644)
thanks all. im going to take another crack at it today. as an aside, how much should one be turning a limit screw? in the Park Tools video it seems he turns it very little, however is there a chance it might need a couple rotations or more to adjust?

my issue is complicated a bit by not having a stand - i feel that would help.

at any rate, i'll be sure to come back and post more pics if the issue remains.

When in doubt, make small adjustments. A full turn of a limit screw is a large adjustment

NYNJrider 05-30-20 02:24 PM

an update.

after fiddling around with it for the better part of two hours yesterday, i got the cage to where it would shift cleanly onto the big chainring but not at all to the lower.

i got fed up and called my shop. brought it in this morning. apparently the FD cage was bent which was leading to the overshifting/chain falling off towards the crank. strangely, i don't recall doing anything that could have led to this but regardless, it seemed to be a relatively simple fix and i was out the door in about 10 minutes.

that said, i do still have chain rub but at least the bike shifts properly from small to large and vice versa.


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