Campy SR Issue, How Best To Resolve?
08-24-09, 05:46 PM
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Campy SR Issue, How Best To Resolve?
I posted this in the mechanics section, but did not get a lot of response. So I thought I'd try here. Looking for suggestions, information, and experience. I have a full 7 speed Super Record Merckx and when I am in high gear I get chain rub against the inside of the outer face of the FD when pedaling hard at the very top of the stroke on the drive side (from 12:00 o'clock to 3:00 o'clock). When pedaling very hard in high gear, I can look down and see the chain move slightly to the right during this quadrant of the pedal stroke. It only occurs during extremely hard pedaling, but that is rather normal for me and I don't want to change my pedal stroke to accommodate the bike. The FD has been adjusted out as far as it can go without coming into contact with the inside of the crank arm and there is still a little rubbing in high gear. Is this likely being caused by crank flex or frame flex or is there some other issue that could be a factor? Is this a bit of a Super Record design problem? I was thinking of trying a narrower chain (9 speed) to see if this might resolve the issue, but I was concerned that a narrower chain might not work so well with the Sachs freewheel. But even if that does resolve the issue, should these clearances normally be this tight? Thanks for any input!
08-24-09, 06:28 PM
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Flex in the drivetrain is not uncommon; probably a little frame, a little crank. You could try spinning the front derailler to optimize clearance.
08-24-09, 06:53 PM
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FWW, I found the same problem on my Rossin.
I have to very carefully adjust it to eliminate the problem, but it can be eliminated.
Check and see if you are as low as you can go on the FD in the braze on. Check the angle that it sits in relation to the crank.
My experience has been that you can eliminate the rub, but the tolerances are extremely small.
You could also probably buff out the small part of the inner crank that rubs. If done right, no one would even notice.
I have to very carefully adjust it to eliminate the problem, but it can be eliminated.
Check and see if you are as low as you can go on the FD in the braze on. Check the angle that it sits in relation to the crank.
My experience has been that you can eliminate the rub, but the tolerances are extremely small.
You could also probably buff out the small part of the inner crank that rubs. If done right, no one would even notice.
08-24-09, 06:58 PM
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The Super Record front derailleur is pretty narrow, and scraping is not uncommon.
08-24-09, 09:35 PM
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I posted this in the mechanics section, but did not get a lot of response. So I thought I'd try here. Looking for suggestions, information, and experience. I have a full 7 speed Super Record Merckx and when I am in high gear I get chain rub against the inside of the outer face of the FD when pedaling hard at the very top of the stroke on the drive side (from 12:00 o'clock to 3:00 o'clock). When pedaling very hard in high gear, I can look down and see the chain move slightly to the right during this quadrant of the pedal stroke. It only occurs during extremely hard pedaling, but that is rather normal for me and I don't want to change my pedal stroke to accommodate the bike. The FD has been adjusted out as far as it can go without coming into contact with the inside of the crank arm and there is still a little rubbing in high gear. Is this likely being caused by crank flex or frame flex or is there some other issue that could be a factor? Is this a bit of a Super Record design problem? I was thinking of trying a narrower chain (9 speed) to see if this might resolve the issue, but I was concerned that a narrower chain might not work so well with the Sachs freewheel. But even if that does resolve the issue, should these clearances normally be this tight? Thanks for any input!
I suspect it's frame flex rather than crank or spindle flex. I'd suggest lowering the derailler to around 1 mm clearance if you can, get it rotationaly aligned right, then if the problem persists open up the limit screw just a bit at a time. The shifting should tolerate a little bit of outward setting without tending to throw the chain into the pedal. If your saddle position could be adjusted to smooth out your stroke a little, that might help, too. You might be mashing just a bit. I have this problem on my Masi sometimes. I don't think it's really your Super Record.
I use a SRAM 951 9-speed chain on bikes with Sachs freewheels regularly, and friction shifting setups. It works beautifully. I don't know if it will help with your problem. I'd get teh FD sorted out as well as possible, first.
Last edited by Road Fan; 08-24-09 at 09:39 PM.
08-25-09, 07:23 AM
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OldSchool
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I suspect it's frame flex rather than crank or spindle flex. I'd suggest lowering the derailler to around 1 mm clearance if you can, get it rotationaly aligned right, then if the problem persists open up the limit screw just a bit at a time. The shifting should tolerate a little bit of outward setting without tending to throw the chain into the pedal. If your saddle position could be adjusted to smooth out your stroke a little, that might help, too. You might be mashing just a bit. I have this problem on my Masi sometimes. I don't think it's really your Super Record.
I use a SRAM 951 9-speed chain on bikes with Sachs freewheels regularly, and friction shifting setups. It works beautifully. I don't know if it will help with your problem. I'd get teh FD sorted out as well as possible, first.
I use a SRAM 951 9-speed chain on bikes with Sachs freewheels regularly, and friction shifting setups. It works beautifully. I don't know if it will help with your problem. I'd get teh FD sorted out as well as possible, first.
I don't believe we inspected the height of the derailleur though. What is gained by just barely clearing the upper limit of the chain with the FD? Is the derailleur a little wider there than lower down and therefore you gain a little lateral clearance because the FD doesn't have to travel as far to the right to move the chain? The FD was contacting the crank arm about 2/3 of the way down the outer derailleur plate, towards the trailing end. These tolerances are all extremely small so perhaps the outer derailleur plate could be adjusted (carefully bent) just a little bit inward at the lower part to provide a little more clearance without creating a problem.
Concerning the use of a narrower chain, since the chain is what is actually coming into contact with the inside of the derailleur, I would think that a little less chain width would provide some additional clearance. We are going to try that later today. However, I was concerned about using the narrower chain with the old SR FD and whether there might be any issues with the FD having to move a little further to take the narrower chain from one ring to the other. Do you find that that is a non issue with your SRAM?
With the most extreme adjustment that we made, the chain did come off once or twice when moving from the low ring to the high ring, but I think I can carefully manage that if I need to. I spend 95% of my time in the top three gears. Is this a bad idea that's going to wind up causing an accident? I know it will require some careful attention when I am moving from low gears to high gears. Is this something I should not compromise on because of safety?
As far as mashing goes, I am sure I do that to some extent. I've been riding for 50 years and I like to push myself in terms of strength and working out. Other than pushing the bike to its limits, is mashing a bad thing, something to be avoided? I'm a little late in the game to find that out.
Your suggestion about seating postiion is interesting also. I would imagine that if the seat is somewhat rearward, that would contribute to the torque being applied sideways to the crank as opposed to a more "over the crank" position where the force is slightly more downward rather than downward and forward. Am I analyzing that properly?
And finally, perhaps another approach to this problem would be to put next generation drive components on the bike. I believe Chorus or Record late 80's early 90's 7 or 8 speed design provided for more clearance at the crank arm (I believe the crank arm was moved slightly farther out from the crank) and probably a bit less flex. I have late 80's 7 speed Chorus on a Bianchi Specialissimo and I have none of these issues with that bike. And I have similar issues on an early 80's SLX Battaglin with SR on it. Seems like more that a coincidence.
I'd be very interested to hear your take on all this. Thanks for posting!
08-25-09, 08:33 AM
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I was at my bike shop owner's house on Sunday and we worked on this with a trial and error approach for about 2 hours. We were doing exactly what you have suggested. We were ever so slightly increasing the outer limit and we almost eliminated the rubbing entirely. The problem is that just when we got to the point where we got complete clearance, the FD started to come into contact with the crank arm because the FD was adjusted out so far.
I lowered the FD mainly on general principles, to ensure I was in-line with Campy's instructions, which can be found on line at their site. It did improve shifting "promptness," implying that overshifting was less necessary. Campy literature also shows that the outer plate should be parallel to the plane of the outer chainline. This will allow you to position the FD cage outward by the maximum amount.
I don't believe we inspected the height of the derailleur though. What is gained by just barely clearing the upper limit of the chain with the FD? Is the derailleur a little wider there than lower down and therefore you gain a little lateral clearance because the FD doesn't have to travel as far to the right to move the chain? The FD was contacting the crank arm about 2/3 of the way down the outer derailleur plate, towards the trailing end. These tolerances are all extremely small so perhaps the outer derailleur plate could be adjusted (carefully bent) just a little bit inward at the lower part to provide a little more clearance without creating a problem.
If this is the case you do not have the derailleur outer plate parallel with the plane of the large chainring. Rotate the FC on the seat tube or in the braze-on tab. On my Mondonico I needed to bend the tab.
Concerning the use of a narrower chain, since the chain is what is actually coming into contact with the inside of the derailleur, I would think that a little less chain width would provide some additional clearance. We are going to try that later today. However, I was concerned about using the narrower chain with the old SR FD and whether there might be any issues with the FD having to move a little further to take the narrower chain from one ring to the other. Do you find that that is a non issue with your SRAM?
I don't find it to be an issue.
With the most extreme adjustment that we made, the chain did come off once or twice when moving from the low ring to the high ring, but I think I can carefully manage that if I need to. I spend 95% of my time in the top three gears. Is this a bad idea that's going to wind up causing an accident? I know it will require some careful attention when I am moving from low gears to high gears. Is this something I should not compromise on because of safety?
I would not compromise on it. One's foot could slip, the chain could cock in the cage and twist it while you try to shift it back onto the sprocket, you could be deprived of propulsion when you really need it, and I hate inconsistent operation.
As far as mashing goes, I am sure I do that to some extent. I've been riding for 50 years and I like to push myself in terms of strength and working out. Other than pushing the bike to its limits, is mashing a bad thing, something to be avoided? I'm a little late in the game to find that out.
The frame flex I'm talking about is caused by the downward force on a pedal tending to flex the BB back and forth, to the left as the right pedal goes down and to the right as the left pedal goes down. If you push harder, due to a pounding pedal stroke or too low a cadence, the degree of deflection is enhanced. Think of the frame as a big stiff spring. Because the BB housing is attached to the seat tube, it pivots side to side. The top of the chainring is therefore moving from side to side, perhaps making the chain touch the cage with every drive side pedal stroke. The pounding is mashing. Spinning is 1) having a smoother stroke that uses more of the rotation to deliver useful power, and 2) using a faster cadence to get the same power with less force on the pedal, and hence frame twist. I'm 56, have ridden a bike most of my life since 5 years old, and I'm improving as I learn more, put all the pieces together in my head, and try to apply it as I ride. You can, too.
Your suggestion about seating postiion is interesting also. I would imagine that if the seat is somewhat rearward, that would contribute to the torque being applied sideways to the crank as opposed to a more "over the crank" position where the force is slightly more downward rather than downward and forward. Am I analyzing that properly?
Here I reach the limits of my analytical ability, so far. I find that small changes in saddle height affect my ability to spin fast and smooth, with a millimeter or three lower being better. The best spin position I've had has been with my knee at KOPS and with my knee angle set at 30 degrees by a professional fitter.
And finally, perhaps another approach to this problem would be to put next generation drive components on the bike. I believe Chorus or Record late 80's early 90's 7 or 8 speed design provided for more clearance at the crank arm (I believe the crank arm was moved slightly farther out from the crank) and probably a bit less flex. I have late 80's 7 speed Chorus on a Bianchi Specialissimo and I have none of these issues with that bike. And I have similar issues on an early 80's SLX Battaglin with SR on it. Seems like more that a coincidence.
If the problem is based on your system setup, that is in common between all three bikes. If the problem is based on frame flex, that can easily be different between the three bikes. If the Merkcx and the Batt both have SLX or SL seat tubes, those are fairly flexy tubesets, compared to an OS tubeset. I'm not familiar with how that Bianchi is made or of what. The Chorus MIGHT have a little more clearance between the crank arm and the chainring than the SR, but you'd need to do some precision measurements to verify that. If you can experiment by moving your Chorus crank over to the Merkcx and then try to set up the SR FD, you'll learn something. But make only one change at a time, so you learn something concrete. Otherwise at the end of the oddyssey you'll just have "well, it worked," or "dang, it didn't." You won't have any new insight.
I'd be very interested to hear your take on all this. Thanks for posting!
I lowered the FD mainly on general principles, to ensure I was in-line with Campy's instructions, which can be found on line at their site. It did improve shifting "promptness," implying that overshifting was less necessary. Campy literature also shows that the outer plate should be parallel to the plane of the outer chainline. This will allow you to position the FD cage outward by the maximum amount.
I don't believe we inspected the height of the derailleur though. What is gained by just barely clearing the upper limit of the chain with the FD? Is the derailleur a little wider there than lower down and therefore you gain a little lateral clearance because the FD doesn't have to travel as far to the right to move the chain? The FD was contacting the crank arm about 2/3 of the way down the outer derailleur plate, towards the trailing end. These tolerances are all extremely small so perhaps the outer derailleur plate could be adjusted (carefully bent) just a little bit inward at the lower part to provide a little more clearance without creating a problem.
If this is the case you do not have the derailleur outer plate parallel with the plane of the large chainring. Rotate the FC on the seat tube or in the braze-on tab. On my Mondonico I needed to bend the tab.
Concerning the use of a narrower chain, since the chain is what is actually coming into contact with the inside of the derailleur, I would think that a little less chain width would provide some additional clearance. We are going to try that later today. However, I was concerned about using the narrower chain with the old SR FD and whether there might be any issues with the FD having to move a little further to take the narrower chain from one ring to the other. Do you find that that is a non issue with your SRAM?
I don't find it to be an issue.
With the most extreme adjustment that we made, the chain did come off once or twice when moving from the low ring to the high ring, but I think I can carefully manage that if I need to. I spend 95% of my time in the top three gears. Is this a bad idea that's going to wind up causing an accident? I know it will require some careful attention when I am moving from low gears to high gears. Is this something I should not compromise on because of safety?
I would not compromise on it. One's foot could slip, the chain could cock in the cage and twist it while you try to shift it back onto the sprocket, you could be deprived of propulsion when you really need it, and I hate inconsistent operation.
As far as mashing goes, I am sure I do that to some extent. I've been riding for 50 years and I like to push myself in terms of strength and working out. Other than pushing the bike to its limits, is mashing a bad thing, something to be avoided? I'm a little late in the game to find that out.
The frame flex I'm talking about is caused by the downward force on a pedal tending to flex the BB back and forth, to the left as the right pedal goes down and to the right as the left pedal goes down. If you push harder, due to a pounding pedal stroke or too low a cadence, the degree of deflection is enhanced. Think of the frame as a big stiff spring. Because the BB housing is attached to the seat tube, it pivots side to side. The top of the chainring is therefore moving from side to side, perhaps making the chain touch the cage with every drive side pedal stroke. The pounding is mashing. Spinning is 1) having a smoother stroke that uses more of the rotation to deliver useful power, and 2) using a faster cadence to get the same power with less force on the pedal, and hence frame twist. I'm 56, have ridden a bike most of my life since 5 years old, and I'm improving as I learn more, put all the pieces together in my head, and try to apply it as I ride. You can, too.
Your suggestion about seating postiion is interesting also. I would imagine that if the seat is somewhat rearward, that would contribute to the torque being applied sideways to the crank as opposed to a more "over the crank" position where the force is slightly more downward rather than downward and forward. Am I analyzing that properly?
Here I reach the limits of my analytical ability, so far. I find that small changes in saddle height affect my ability to spin fast and smooth, with a millimeter or three lower being better. The best spin position I've had has been with my knee at KOPS and with my knee angle set at 30 degrees by a professional fitter.
And finally, perhaps another approach to this problem would be to put next generation drive components on the bike. I believe Chorus or Record late 80's early 90's 7 or 8 speed design provided for more clearance at the crank arm (I believe the crank arm was moved slightly farther out from the crank) and probably a bit less flex. I have late 80's 7 speed Chorus on a Bianchi Specialissimo and I have none of these issues with that bike. And I have similar issues on an early 80's SLX Battaglin with SR on it. Seems like more that a coincidence.
If the problem is based on your system setup, that is in common between all three bikes. If the problem is based on frame flex, that can easily be different between the three bikes. If the Merkcx and the Batt both have SLX or SL seat tubes, those are fairly flexy tubesets, compared to an OS tubeset. I'm not familiar with how that Bianchi is made or of what. The Chorus MIGHT have a little more clearance between the crank arm and the chainring than the SR, but you'd need to do some precision measurements to verify that. If you can experiment by moving your Chorus crank over to the Merkcx and then try to set up the SR FD, you'll learn something. But make only one change at a time, so you learn something concrete. Otherwise at the end of the oddyssey you'll just have "well, it worked," or "dang, it didn't." You won't have any new insight.
I'd be very interested to hear your take on all this. Thanks for posting!
08-25-09, 08:58 AM
#8
OldSchool
Thread Starter
If the problem is based on your system setup, that is in common between all three bikes. If the problem is based on frame flex, that can easily be different between the three bikes. If the Merkcx and the Batt both have SLX or SL seat tubes, those are fairly flexy tubesets, compared to an OS tubeset. I'm not familiar with how that Bianchi is made or of what. The Chorus MIGHT have a little more clearance between the crank arm and the chainring than the SR, but you'd need to do some precision measurements to verify that. If you can experiment by moving your Chorus crank over to the Merkcx and then try to set up the SR FD, you'll learn something. But make only one change at a time, so you learn something concrete. Otherwise at the end of the oddyssey you'll just have "well, it worked," or "dang, it didn't." You won't have any new insight.
Glad to help! PM me if you think this is all getting too long.
Glad to help! PM me if you think this is all getting too long.
First, I will definitely eliminate the possibility of the chain coming off the large ring. That's really a no brainer once I started to think about it a little.
Second, I will more closely analyze the parallel positioning of the FD and make any adjustments necessary to achieve the maximum clearance while maintaining the shifting integrity onto the large ring.
Third, the Bianchi I have is late 80's and it is also SLX. The Merckx is SL and the Batt is SLX, so the comparisons are fairly apples to apples as far as frame material is concerned.
I agree on making only one change at a time and then reviewing. The same approach applies to resolving computer problems which is what I do for a living. You try to simplify things as much as possible, then change one thing at a time and note any effect brought about by that change. My plan would be to put a different crank and then perhaps a different bottom bracket on the frame and see what happens after each change. I think that may tell me quite a bit about the source of the problem. Thanks again for taking such an interest.
