Gear Shifting Issue

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Rhyagelle

Member
Hello,

Last year I crashed my bike and hurt myself pretty bad, though the bike escaped it relatively well (only 1 piece got bent). I left the bike in storage and finally came off of therapy around Oct of 2021 fit. I wanted to get my bike going again, and replaced the piece that was snapped on it (nothing else seemed to be an issue). It was the hanger piece in the back, that holds the rear derailleur to the bike itself. I made sure it was the right piece for my bike, by contacting the place I bought the bike and Polygon. They both confirmed that was it. I replaced it and put it all back together.

My first round of headaches began with a really loud, annoying noise trying to pedal. I fixed that by re-attaching the wheel on. My next headache began with the front derailleur cage. My chain is hitting the bottom of it, and I can't seem to shift the clamp for the cage and further down to improve this. I was pointed out to try shifting so that the bike isn't on both smallest cogs on rear and front, and when I tried to do that, the front gear wouldn't shift. It allows me to "move" it on the shifter by the handles (I see it moving) but it won't actually shift to any gears on the front, so it's stuck.

So those are my 2 current issues. I have no idea what to do. I've watched Park Tool videos on adjusting derailleurs, but it hasn't helped at all. Anyone know what I could be doing wrong? I left a video of the noise it's making and pictures of the chain lying on the cage. Beyond that, I don't know how to capture images/videos of the issue of it not shifting.

(yes, the bike is a bit dirty. I haven't used it since the crash lol)
06Gisrn.jpg

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(I do not live near any bike repair shops, so unfortunately that is out of the question for me)

Thank you for reading~
 

Ajax Bay

Guru
Location
East Devon
:welcome:Sounds as if your front derailleur (FD) has slipped lower on the seat tube in the crash (glad you're back on your bike). Unclamp the cable, loosen the bolt which tightens the band around the tube and slide it up. Manually push the cage across above the large chainring and set and secure the FD band at a vertical position which allows 1-2mm between the bottom of the cage and the teeth of the chainring. Reset the FD in the normal way.
I have not looked at your video so I may not have understood.
https://si.shimano.com/api/publish/storage/pdf/en/si/P-26/SI-P-26-000-00-ENG.pdf
 
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Rhyagelle

Rhyagelle

Member
Hello,

First, let me say thank you Ajax Bay!!!

I had to undo the pinch nut holding the cable, as it wouldn't let me lower the cage until I did, but once I undid the pinch nut, I was able to shift the cage up and down via the clamp on the bike tube. That brought back the ability to shift to Gear 1 on the left hand (front)! That was one of the other issues, and now I can "erase" it with this procedure.

However, I still have the conundrum of the cage height. I did as you suggested and unclamped it and lowered it, which does work! But upon tightening the clamp to keep that corrected height, it causes the cage to lift up again and the chains to rub against the bottom of the cage, which also "disables" Gear 1 on left (front) until I re-adjust it lower again. It takes forever to adjust it so no gear is rubbing on the side of the cage too and when I do finally adjust it, tightening the clamp once again causes it to go up an incredibly amount. Once again bringing back the bottom chain rub.

I'm almost at my wits end. I want to try and force hold it down while I tighten the clamp, but I'm afraid I might damage the FD. 😓
 

cyberknight

As long as I breathe, I attack.
:welcome:Sounds as if your front derailleur (FD) has slipped lower on the seat tube in the crash (glad you're back on your bike). Unclamp the cable, loosen the bolt which tightens the band around the tube and slide it up. Manually push the cage across above the large chainring and set and secure the FD band at a vertical position which allows 1-2mm between the bottom of the cage and the teeth of the chainring. Reset the FD in the normal way.
I have not looked at your video so I may not have understood.
https://si.shimano.com/api/publish/storage/pdf/en/si/P-26/SI-P-26-000-00-ENG.pdf
i might be wrong but looks like its hitting the bottom of the cage which means its to high ? so it needs pushing down ?
1649622551895.png
 
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Rhyagelle

Rhyagelle

Member
I'm not sure how to find the make and model on the bike, but I did find the only text on the FD clamp. It says, "Shimano ACERA" and the RD says, "TourneyTX".

If it helps any, I have this bike but I guess the first 2021 revision model, as mine was green (called "2021 Polygon Cascade 4.0 - 27.5 inch Mountain Bike - Size: S" in my order page).

https://www.bikesonline.com/2021-polygon-cascade-4-black-27.5inch-mountain-bik

Sorry for post delays. I need moderator approval for them to appear. I made another post above with details on the situation that hasn't been approved yet.
 
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Rhyagelle

Rhyagelle

Member
Hello,

Thank you for the PDF. I just quickly glanced through it (gonna DL to phone) and try to it out. Hopefully this will help me figure out why it (the clamp) won't stay shifted down.

As for a LBS/BS, I do not have any near me. The closest is a couple counties away, and I do not possess a car. 😓
 
D

Deleted member 1258

Guest
Hello,

Thank you for the PDF. I just quickly glanced through it (gonna DL to phone) and try to it out. Hopefully this will help me figure out why it (the clamp) won't stay shifted down.

As for a LBS/BS, I do not have any near me. The closest is a couple counties away, and I do not possess a car. 😓

Have a look at this guide, normally with a double chainset and the chain on the inner chain ring I'll adjust the height so I can just get a 2 pence piece edgeways between the outer chain ring and the bottom of the front changer.

https://www.parktool.com/blog/repair-help/front-derailleur-adjustment#article-section-2
 
If you crashed on the righthand side and broke the mech hanger then it sounds like you've also bent the front derailleur a fraction as it worked before the crash and doesn't work now.
A quick check, the chain moves down 2mm per tooth difference.
You have an 18 tooth difference between big and small chainrings.
So the chain will drop 36mm shifting from big to the small chainring.
If you think the derailleur is in the right place then put the chain on the big chainring and measure the gap between the chain and the bottom of the cage.
As the derailleur can cope with a 20 tooth difference then it should be +40mm gap.
If it's less then the derailleur may well be a bit twisted somewhere.

Luck ......... ^_^
 
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Rhyagelle

Rhyagelle

Member
Have a look at this guide, normally with a double chainset and the chain on the inner chain ring I'll adjust the height so I can just get a 2 pence piece edgeways between the outer chain ring and the bottom of the front changer.

https://www.parktool.com/blog/repair-help/front-derailleur-adjustment#article-section-2

I'll have a look now, thank you! I've got it on my phone and will run over to my bike after this post has been posted.

If you crashed on the righthand side and broke the mech hanger then it sounds like you've also bent the front derailleur a fraction as it worked before the crash and doesn't work now.
A quick check, the chain moves down 2mm per tooth difference.
You have an 18 tooth difference between big and small chainrings.
So the chain will drop 36mm shifting from big to the small chainring.
If you think the derailleur is in the right place then put the chain on the big chainring and measure the gap between the chain and the bottom of the cage.
As the derailleur can cope with a 20 tooth difference then it should be +40mm gap.
If it's less then the derailleur may well be a bit twisted somewhere.

Luck ......... ^_^

When I crashed, it was more of a skid and it was on the left hand side. I don't think the FD looks bent or anything, but it sure would suck if that was the case. I have no idea how to replace them nor how much they cost. I'm really, really hoping I didn't break it in the crash.

I'll go try what you suggested, too! Fingers crossed!

EDIT

Okay, I can adjust it finally for height, but no matter what I do, one gear is always grinding the sides. I also noticed that even if I tighten the clamp, I can change the angle of the cage very easily just by bumping it. It's absolutely frustrating. I try to keep it still, and tightening just completely changes the height and angle and there's no way to stop it. So I don't know, maybe it is broken.

If this clamp piece IS broken, where can I get a replacement? Does it HAVE to be the same Shimano ACERA?
 
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Ajax Bay

Guru
Location
East Devon
An Acera FD is inexpensive. But they are robust so this really sounds like you just need to unclamp the cable, half remove (loosen band clamp bolt) refit it at the right height to clear the large ring, secure band, and clamp cable so there's just tension in the cable when the chain is on small ring (to large sprocket) and the lower limit screw allows <1mm of clearance between the cage side and the chain.
https://www.tredz.co.uk/.Shimano-Acera-M3000-Triple-Front-Derailleur-Top-Swing_92573.htm
If you cannot get to an LBS, then surely there must be a rider local to you with this basic competence.
 
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Rhyagelle

Rhyagelle

Member
An Acera FD is inexpensive. But they are robust so this really sounds like you just need to unclamp the cable, half remove (loosen band clamp bolt) refit it at the right height to clear the large ring, secure band, and clamp cable so there's just tension in the cable when the chain is on small ring (to large sprocket) and the lower limit screw allows <1mm of clearance between the cage side and the chain.
https://www.tredz.co.uk/.Shimano-Acera-M3000-Triple-Front-Derailleur-Top-Swing_92573.htm
If you cannot get to an LBS, then surely there must be a rider local to you with this basic competence.

Oh thank god, it is pretty inexpensive! Thank you so much for including the link! If I needed to replace this, is there a guide I read/watch about how to remove the old one from the bike? I'm assuming I have to take chainring off near the pedals for it, but being a newb, I'm not sure.

As for the clamp, the problem is that it shifts the angle and height of the cage even when fully tightened very easily when the nut is being tightened or if I accidentally bump it. Basically, it's extremely easy for this thing to shift angle/height even when fully tightened. And when I can finally adjust to the proper looking height (trying the penny on the ring trick thingy), gear 2 or gear 1 is rubbing heavily on the side of the cage but angling it so it doesn't rub on gear 2/1 then causes gear 3 to rub on the left-hand side. I'll keep messing with it, hopefully it's just a really frustrating job to do and it's supposed to be this way...

I don't know any people who rides bikes, live atop a mountain full of very, very old people. I'm not sure how I could go about checking, but I guess I could ask the local car shop if they know anyone.
 

Ajax Bay

Guru
Location
East Devon
I have already shared (post #7 above) the Technical Sheet (TS) which gives one instructions (which you can use to set up your current one btw).
No, the chainset does not have to come off.
If the height/angle of the cage is shifting "very easily" you have not tightened the band-on bolt sufficiently. Fully fully tighten it, once it is the correct height and the cage is aligned with the chainrings (again TS makes clear with 'easy to understand diagrams'). And, yes, take care while tightening NOT to allow any vertical or rotational movement.
Don't "accidentally bump it" when it's not fully secure.
"I live atop a mountain full of very, very old people." I suspect that many of the posters on here (including me) you'd likely describe as 'really old people': just guessing ;).
 
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Rhyagelle

Rhyagelle

Member
I have already shared (post #7 above) the Technical Sheet (TS) which gives one instructions (which you can use to set up your current one btw).
No, the chainset does not have to come off.
If the height/angle of the cage is shifting "very easily" you have not tightened the band-on bolt sufficiently. Fully fully tighten it, once it is the correct height and the cage is aligned with the chainrings (again TS makes clear with 'easy to understand diagrams'). And, yes, take care while tightening NOT to allow any vertical or rotational movement.
Don't "accidentally bump it" when it's not fully secure.
"I live atop a mountain full of very, very old people." I suspect that many of the posters on here (including me) you'd likely describe as 'really old people': just guessing ;).

Yea, I saw it too late. Made the last post and then went over to the bike with the phone on hand and saw it. Sorry about that!

I think it might be the nut itself preventing me from tightening it completely. I just noticed it doesn't go in all of the way, sorta loose, so clamping to full force is not possible. It's almost like it's threaded wrong, but if I take the FD off completely, the nut goes into its position just fine. Just won't do it when it's actually attached to the bike pipe. I also noticed two pieces on the inner part of the clamp that keeps moving up and down, and are held down by 1 little piece of white double-sided tape and it's just not holding it down well at all.

Well, by old I mean people over their seventies and eighties. Some of my neighbors even fought in WW2. :sweat:

EDIT

here are some pics of the piece unattached to the bike. A separate plastic piece that goes on the inside falls off easily because of a single 1 sided piece of tape.

 
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