Chain length and RD tension?
02-14-22, 08:32 PM
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Chain length and RD tension?
I switch from a mid-compact 52-36 to a compact 50-34 and expected to see the chain sag and pulley cage tipped back in the 34-11 but I see neither--there appears to be decent downward tension on the cage (pulled below horizontal). In the 50-30, the cage is vertical. I neglected to check the two cage positions before swapping the chainrings. Perhaps the chain was a tad on the short end with the 52-36? Or, there's not enough diff in teeth or diameter in the old/new rings to affect the RD cage's angle? I'm guess going to keep the chain length as it unless it's reco'd to shorten a link. How much RD cage angle do you folks like in the big-big combo? Thoughts?
02-14-22, 08:48 PM
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How does the system shift now? It sounds like there's no problem. Andy
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AndrewRStewart
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02-14-22, 09:04 PM
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Dropping two teeth on the chainring isn't going to meaningfully change anything. Always check chain length if you go bigger, of course.
Sometimes I will leave the chain one link longer than absolutely necessary so the rear derailer cage isn't pulled taught. I'm not sure if this is actually "nicer" to the RD, but it feels that way.
Sometimes I will leave the chain one link longer than absolutely necessary so the rear derailer cage isn't pulled taught. I'm not sure if this is actually "nicer" to the RD, but it feels that way.
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02-15-22, 01:03 AM
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Since the chain was likely sized to the big/big combo, you'd only see sag on the small/small side of it if you were already at the absolute limits of the RD's chainwrap capacity.
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Last edited by urbanknight; 02-15-22 at 02:16 AM.
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02-15-22, 01:59 AM
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It's perfect--which is what made me wonder, lol. It's the easiest mod I've ever done--pull crank, swap rings, slide FD down a couple mm to smaller diameter of the big ring--that was it--no cable adjustment, nothing more!
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02-15-22, 09:16 AM
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If the front shifter is an indexed type and if the cable is not routed with full length casing then lowering the ft der will have the effect of loosening the ft der index adjustment. If there is enough barrel adjuster range a simple cable tension adjustment likely will be needed. If the cable is looser than the original and if the original cable adjustment was good the cage travel during shifting won't otherwise be the same. Andy
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02-16-22, 06:46 PM
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If the front shifter is an indexed type and if the cable is not routed with full length casing then lowering the ft der will have the effect of loosening the ft der index adjustment. If there is enough barrel adjuster range a simple cable tension adjustment likely will be needed. If the cable is looser than the original and if the original cable adjustment was good the cage travel during shifting won't otherwise be the same. Andy
