cause of chain gliding over small chainring
03-14-15, 09:51 PM
#1
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cause of chain gliding over small chainring
I went for my first ride on my winter restoration project. Campy Record crankset (1980s). As shown in this blurry pic, a few times the chain just wouldn't catch and glided over the small chain ring. Once I literally had to stop, get off the bike, and guide the chain on with my hand. The front derailleur stops appear to be good. The chain is a brand new KMC 6/7 speed. Any ideas?
03-14-15, 10:00 PM
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Your chain is too narrow for the gap between the rings. That allows the tips of the teeth to snag it between the plates, while it's supported by the inside face of the outer ring. If the gap were narrower, or more logically, the chain were wider it would push over and the teeth would drop into the chain.
FYI - 7/6s chains are made around the spacing of 7s and ultra 6s sprockets. For this older bike, you want a chain that says 6s or 6s/5s to get the added width needed.
FYI - 7/6s chains are made around the spacing of 7s and ultra 6s sprockets. For this older bike, you want a chain that says 6s or 6s/5s to get the added width needed.
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Just because I'm tired of arguing, doesn't mean you're right.
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WARNING, I'm from New York. Thin skinned people should maintain safe distance.
Last edited by FBinNY; 03-14-15 at 10:03 PM.
03-14-15, 10:21 PM
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You are shifting it too slowly..or not all the way. Try pushing the shifter all the way down at once and then bring back to trim it.
03-15-15, 05:46 AM
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Besides the above suggestions, maybe your low limit screw is not adjusted as well as you think. I set it up by shifting into small front, large rear and setting the stop for a fraction of a millimeter of cage clearance at the tightest point; you don't need much.
03-15-15, 07:12 AM
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Your chain is too narrow for the gap between the rings. That allows the tips of the teeth to snag it between the plates, while it's supported by the inside face of the outer ring. If the gap were narrower, or more logically, the chain were wider it would push over and the teeth would drop into the chain.
FYI - 7/6s chains are made around the spacing of 7s and ultra 6s sprockets. For this older bike, you want a chain that says 6s or 6s/5s to get the added width needed.
FYI - 7/6s chains are made around the spacing of 7s and ultra 6s sprockets. For this older bike, you want a chain that says 6s or 6s/5s to get the added width needed.
03-15-15, 10:36 AM
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just a thought...
if the chainrings were removed, you might want to check that they were re-installed properly. but before doing that i would remove the chain, spin the crank and peer down from above looking for anything suspicious, like the gap between the large and small chain varying by an abnormal amount.
if the chainrings were removed, you might want to check that they were re-installed properly. but before doing that i would remove the chain, spin the crank and peer down from above looking for anything suspicious, like the gap between the large and small chain varying by an abnormal amount.
03-15-15, 03:11 PM
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03-16-15, 10:41 PM
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Your chain is too narrow for the gap between the rings. That allows the tips of the teeth to snag it between the plates, while it's supported by the inside face of the outer ring. If the gap were narrower, or more logically, the chain were wider it would push over and the teeth would drop into the chain.
FYI - 7/6s chains are made around the spacing of 7s and ultra 6s sprockets. For this older bike, you want a chain that says 6s or 6s/5s to get the added width needed.
FYI - 7/6s chains are made around the spacing of 7s and ultra 6s sprockets. For this older bike, you want a chain that says 6s or 6s/5s to get the added width needed.
But this is kind of messed up. Are you saying my Campy Record 42/52 crankset is not compatible if I want to run a 7-speed freewheel in the back??
03-16-15, 10:57 PM
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No, But with the wider spacing of the rings, to allow for the older and wider chains, there will be a greater likelihood of the chain riding the tops of the teeth. More so with slow shifting, less ft der cage inward movement, cross chaining, shifting under power of at slow rpms. The photo shows that the inner ring is correctly mounted but I can't tell about the large ring. Andy.
03-16-15, 11:11 PM
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Odds are your crankset dates back to the 5s/6s era, which is why the separation is wide for a 7s/8s chain. If you have access to a belt sander you can remove the inner ring and remove some material from the inner (toward the other ring) surface working the ring in overlapping zones so it stays uniform. No great precision is needed, or you can use a caliper to keep it uniformly thick. You want to remove about 3/4mm to bring the tips of the teeth closer to the outer ring. I've done this and it's fast and easy, simply laying the ring flat and pRessing. WARNING -- IT GETS HOT FAST.
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FB
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An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
