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Chain sits on top of chainring when shifting up
#1
Hey guys,

First post here. I've tried searching, but I don't know what you call this.

I have a vintage Schwinn Passage that I picked up a few months ago. At first it worked well, but recently it's been giving me trouble.

When I shift, the chain pops into the higher (larger) gear, but then sits on top of the chain ring. What ends up happening is that the chainring will keep turning, and eventually the chain will pop into place or pop right off.

[Image: 5f9NtSN.jpg]

I have replaced the rear derailleur, adjusted the F&R derailleurs, and just replaced the Chain because the last one was right at the edge of needing replacement. The problem still persists. I assume the fault has to be in the front derailleur or the chain ring.

Any idea of what is happening?

Mike
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#2
what are the specs of the chain you put on?
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
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#3
(02-18-2014, 11:27 PM)painkiller Wrote:  what are the specs of the chain you put on?

I got a SRAM PC 850 P-Link Bicycle Chain meant for 6,7, and 8 speed bikes. I have a 6 cog cassette.

The old chain acted the same way. This one is much smoother, but that's also because it came well greased.
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#4
First double check that the FD was not bumped, and rotated slightly on the seat post.

If not, then I believe the FD needs a slight (less than ¼ turn) adjustment to allow it to push the chain further.

FYI: chains need to be wiped down with a rag, lubricated with a light oil, run through all the gears, then wiped off chain. You want the oil to get to the inside, and remove any left on the outside. All the stuff on the outside does is attract dirt. This should be done about once per month, more if you ride in harsh conditions.
Nigel
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#5
Your photo left out the most important part of the issue - the front derailleur. If the same happened on 2 chains it has to be either chainwheel or derailleurs. If it does not happen at the same point on the chainwheel (from a bent/damaged tooth) then it has to be the derailleur. What is happening is that the chain side plates are riding on the teeth instead of the rollers as a result of not enough side movement to complete a shift. Google "adjust front derailleur" and start from the beginning, including correct position. Sheldonbrown.com and parktool.com/blog are the first results to check out.
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#6
So, since I have friction shifters, this could be due to me not using enough force to shift?

I'll take a pic of the front derailleur tonight!
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#7
NO - don't know how you could reach that conclusion from any of the posts above. The derailleur moves out to the outer stop when you pull on the lever - does not matter how hard you push, won't go further. If you sift too slowly you MAY not get as good a shift.

Although a pic that included the derailleur might have helped some initially, at this point it will not help as much as you going through the derailleur adjustment process. Also, when looking at a problem one needs to approach it methodically/logically. The chainring receives the chain from the top of the rear cogs, and the rear derailleur feeds the chain onto the bottom of the cogs, so it it not possible for the rear derailleur to have anything to do with your problem.
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#8
I replaced the rear derailleur because it was bent and lacked the adjustability of a new unit.

I have adjusted both the front and rear derailleurs to shift though all of the gears, but not far enough where they can push the chain off the chainring or cassette.

I'll play with the positioning of the front derailleur.
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#9
(02-19-2014, 04:38 PM)so2002 Wrote:  .....
I'll play with the positioning of the front derailleur.

By "play" you hopefully mean carefully measure and adjust; or you will just end up paying someone to fix it.
Nigel
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#10
(02-19-2014, 04:38 PM)so2002 Wrote:  I'll play with the positioning of the front derailleur.
Unless you can confirm that you followed, from start to finish, instructions for derailleur positioning and adjustment we have no reference point when you say you adjusted the derailleur and you will "play" with the positioning. Mechanical systems require a methodical approach, and standard procedures, especially when trying to diagnose remotely.
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#11
(02-20-2014, 09:11 AM)cny-man Wrote:  
(02-19-2014, 04:38 PM)so2002 Wrote:  I'll play with the positioning of the front derailleur.
Unless you can confirm that you followed, from start to finish, instructions for derailleur positioning and adjustment we have no reference point when you say you adjusted the derailleur and you will "play" with the positioning. Mechanical systems require a methodical approach, and standard procedures, especially when trying to diagnose remotely.

I followed Alton Brown's steps, having adjusted the rear derailleur first. I then position the front derailleur such that it is straight, and 2-3mm from the biggest chainring.
[Image: 5r9kDW0l.jpg]

Here's what it looks like from above:
[Image: 0fIS6hwl.jpg]

And the side:
[Image: bE0DsLyl.jpg]

I think my Chainring looks okay:
[Image: FPqpMlGl.jpg]

But it still keeps doing this:
[Image: lF2aCrfl.jpg]

And writing that strangely felt like a buzzfeed post. Any suggestions would be appreciated.

Mike
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#12
Hi Mike;

Your FD needs to push the chain another 0.1mm or so to the right during shifting.

The PC 850 chain's width is 0.7mm narrower than a 6 speed chain.

From: http://en.wikipedia.org/wiki/Bicycle_chain#Width

6 speed - 7.8mm (all brands)
7 speed - 7.3mm (all brands)
8 speed - 7.1mm (all brands)
9 speed - 6.6 to 6.8mm (all brands)
10 speed - 6.2mm (Shimano, Campagnolo)
10 speed(Narrow) - 5.88mm (Campagnolo, KMC)
10 speed(Narrow, Direction) - 5.88mm (Shimano CN-5700,CN-6700,CN-7900)
11 speed - 5.5mm (Campagnolo, KMC, Shimano CN-9000)

Based on the above information; your FD needs to push the chain 0.35mm (= (7.8-7.1)/2) further to the right when up shifting than it would for a six speed chain. Same on down shifting.
Nigel
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#13
Does that mean I have the wrong Chain? Putting a lot of pressure on the FD does not help, and I have tried setting it so that it can put the chain far enough that it starts binding on the other side.
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#14
(02-24-2014, 07:24 PM)so2002 Wrote:  Does that mean I have the wrong Chain? Putting a lot of pressure on the FD does not help, and I have tried setting it so that it can put the chain far enough that it starts binding on the other side.

The chain is fine. You need to adjust the H limit screw so that the cage can travel a little bit further. It has nothing to do with putting a lot of pressure on it.

If you go to far with the H limit screw, the chain will fall off on the outside (right side) of the chain ring.

When shifting, you have to put it a little past the nominal set point, then bring it back a fraction.
Nigel
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#15
So, it's normal working condition, I just have to be more rough with it?
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#16
(02-25-2014, 05:00 PM)so2002 Wrote:  So, it's normal working condition, I just have to be more rough with it?
NO !!!

You need to adjust the H limit screw so that the cage can travel a little bit further. It has nothing to do with putting a lot of pressure on it.

Please READ.
Nigel
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#17
I understand about the limit screw, I've currently got mine set to the point that it just barely wont push the chain off the chainring.

I say rough, because unless I put extra pressure on it, the chain takes 1/2 a revolution (where it sits on top) to fall into place.
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#18
It seems very odd that the first couple links feed on but then the following ones don't. The chainwheel teeth look pretty worn, even chewed up, but something else is probably being missed. Why not seek some in-person assistance - bike co-op, knowledgeable friend, etc?
The chainwheel teeth look pretty worn, even chewed up, but something else is probably being missed. Why not seek some in-person assistance - bike co-op, knowledgeable friend, etc? I'm betting the right set of eyes and hands on the bike could figure this out in short order.
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