Chain length
04-16-15, 09:40 AM
#26
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Looking at your latest photos, I'm seeing that you stretched the chain 3 links at the chainwheels, not two!
That chain is really sagging, not what I expected to see. Remember that the fine-tuning of axle position is critically the "last word" on how the limits of "chain tension" are tuned at both extremes of "gear" selection.
You only have to move the axle 1/4" in one direction or the other for an entire 1/2" link to be taken up or added.
That is a great-looking crankset btw!
That chain is really sagging, not what I expected to see. Remember that the fine-tuning of axle position is critically the "last word" on how the limits of "chain tension" are tuned at both extremes of "gear" selection.
You only have to move the axle 1/4" in one direction or the other for an entire 1/2" link to be taken up or added.
That is a great-looking crankset btw!
Last edited by dddd; 04-16-15 at 09:44 AM.
04-16-15, 04:36 PM
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Yes, but that chain was made three links longer for the photos, so has the chain sagging greatly more than with just a 2-link addition!
Look closely, you'll see that the chain cannot possibly be joined at the tested length, without some sort of gender-bending half-link.
Edit: Looking more closely, and at the inner and outer links along the chainring, I see you are right, that it was a two-link addition.
Have you had any luck skooching the axle either way? Right to the limit of where the rear derailer begins losing tension on the small-small combo...
Look closely, you'll see that the chain cannot possibly be joined at the tested length, without some sort of gender-bending half-link.
Edit: Looking more closely, and at the inner and outer links along the chainring, I see you are right, that it was a two-link addition.
Have you had any luck skooching the axle either way? Right to the limit of where the rear derailer begins losing tension on the small-small combo...
Last edited by dddd; 04-16-15 at 04:41 PM. Reason: Mis-judged the photo
04-17-15, 07:25 AM
#29
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04-17-15, 09:08 AM
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Your last photo isn't angled to show the limit of contact with the bottom run of the left dropout's flat surfaces. It may be fine unless the actual gripping surfaces of the axle locknut are running off of the forward edge of the lower half of the dropout.
Remember that the axle gripping surface contact between the axle locknut and the dropout is much more critical than is the gripping surface of the head of the QR lever, since there is free-play between the axle and the QR mechanism.
Remember also that the loadings that might cause an axle end to slip along the dropout tend to be much more critical on the drive side of the axle.
It would be useful at this point to observe and possibly photograph the dropout/axle engagement from below and forward of the dropout. Good photos so far otherwise!
Is your bike one of the Austrian-built bikes? Mine has a very different-looking dropout attachment to the stays (appears to be welded), and btw I was able to use the PC950 model chain (even narrower) on the old Agrati-pattern chainrings.
Remember that the axle gripping surface contact between the axle locknut and the dropout is much more critical than is the gripping surface of the head of the QR lever, since there is free-play between the axle and the QR mechanism.
Remember also that the loadings that might cause an axle end to slip along the dropout tend to be much more critical on the drive side of the axle.
It would be useful at this point to observe and possibly photograph the dropout/axle engagement from below and forward of the dropout. Good photos so far otherwise!
Is your bike one of the Austrian-built bikes? Mine has a very different-looking dropout attachment to the stays (appears to be welded), and btw I was able to use the PC950 model chain (even narrower) on the old Agrati-pattern chainrings.
Last edited by dddd; 04-17-15 at 09:13 AM.
04-17-15, 09:51 AM
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Some useful info from a thread I posted a while ago regarding my Pinarello, but mirrors a lot of what's already been said:
https://www.bikeforums.net/classic-vi...pinarello.html
With better weather finally here, I was actually just working on my own chain length issue (from the above thread) and resolving it based on the info (mainly lengthening the chain). Upon removing the RD I realized that the cage spring hadn't been tensioned correctly and that was what was causing the issue (the chain was also too short but it was the RD that was the main culprit, it wasn't pulling back enough when in small/small and causing the slack in small/small).
Might be worth looking into -- either an incorrectly installed spring, a slipped one, or just a gummed up one in the RD. Miamijim's post with the pics in my thread was helpful to show what it should look like in the small/small (pulleys pretty much horizontal), and if it can't do that it could be the RD and the spring. (Though I could be wrong about this particular derailleur, as it's older than mine.)
https://www.bikeforums.net/classic-vi...pinarello.html
With better weather finally here, I was actually just working on my own chain length issue (from the above thread) and resolving it based on the info (mainly lengthening the chain). Upon removing the RD I realized that the cage spring hadn't been tensioned correctly and that was what was causing the issue (the chain was also too short but it was the RD that was the main culprit, it wasn't pulling back enough when in small/small and causing the slack in small/small).
Might be worth looking into -- either an incorrectly installed spring, a slipped one, or just a gummed up one in the RD. Miamijim's post with the pics in my thread was helpful to show what it should look like in the small/small (pulleys pretty much horizontal), and if it can't do that it could be the RD and the spring. (Though I could be wrong about this particular derailleur, as it's older than mine.)
04-17-15, 09:53 AM
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It would be useful at this point to observe and possibly photograph the dropout/axle engagement from below and forward of the dropout. Good photos so far otherwise!
Is your bike one of the Austrian-built bikes? Mine has a very different-looking dropout attachment to the stays (appears to be welded), and btw I was able to use the PC950 model chain (even narrower) on the old Agrati-pattern chainrings.
Is your bike one of the Austrian-built bikes? Mine has a very different-looking dropout attachment to the stays (appears to be welded), and btw I was able to use the PC950 model chain (even narrower) on the old Agrati-pattern chainrings.
Yes, Austrian built Sears badged bike.
04-17-15, 10:10 AM
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Some useful info from a thread I posted a while ago regarding my Pinarello, but mirrors a lot of what's already been said:
https://www.bikeforums.net/classic-vi...pinarello.html
With better weather finally here, I was actually just working on my own chain length issue (from the above thread) and resolving it based on the info (mainly lengthening the chain). Upon removing the RD I realized that the cage spring hadn't been tensioned correctly and that was what was causing the issue (the chain was also too short but it was the RD that was the main culprit, it wasn't pulling back enough when in small/small and causing the slack in small/small).
Might be worth looking into -- either an incorrectly installed spring, a slipped one, or just a gummed up one in the RD. Miamijim's post with the pics in my thread was helpful to show what it should look like in the small/small (pulleys pretty much horizontal), and if it can't do that it could be the RD and the spring. (Though I could be wrong about this particular derailleur, as it's older than mine.)
https://www.bikeforums.net/classic-vi...pinarello.html
With better weather finally here, I was actually just working on my own chain length issue (from the above thread) and resolving it based on the info (mainly lengthening the chain). Upon removing the RD I realized that the cage spring hadn't been tensioned correctly and that was what was causing the issue (the chain was also too short but it was the RD that was the main culprit, it wasn't pulling back enough when in small/small and causing the slack in small/small).
Might be worth looking into -- either an incorrectly installed spring, a slipped one, or just a gummed up one in the RD. Miamijim's post with the pics in my thread was helpful to show what it should look like in the small/small (pulleys pretty much horizontal), and if it can't do that it could be the RD and the spring. (Though I could be wrong about this particular derailleur, as it's older than mine.)
Good info on that link, all of this is making my brain hurt.
04-17-15, 10:16 AM
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I did.
I cheated and rode this into work today (@9 miles). Took the 'scootch' out, went with the length I had it. Not to disregard everybody's advice, I just wanted to ride the darn bike!
So I'll put it back up on the stand and go over it this weekend, there may be something I'm missing or a tweak I can do to the RD that will help. I may have it adjusted goofy, I dunno.
Earlier in the thread I mentioned I find I ride mostly on the big ring up front, today I found I was on the small one the entire time. So this may be a choice of where I'm living in the gears.
I cheated and rode this into work today (@9 miles). Took the 'scootch' out, went with the length I had it. Not to disregard everybody's advice, I just wanted to ride the darn bike!
So I'll put it back up on the stand and go over it this weekend, there may be something I'm missing or a tweak I can do to the RD that will help. I may have it adjusted goofy, I dunno.
Earlier in the thread I mentioned I find I ride mostly on the big ring up front, today I found I was on the small one the entire time. So this may be a choice of where I'm living in the gears.
