Minimum Chainring Tooth Difference?
02-27-16, 12:39 PM
#1
Living 'n Dying in ¾-Time
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Minimum Chainring Tooth Difference?
In general, is there a minimum chainring tooth difference for C&V front derailleurs?
Specifically, can a Shimano Dura-Ace FD-7400 shift correctly between a 40T outer chainring and a 34T inner chainring? It would be paired with a Shimano Dura-Ace 7401, which will be shifting (friction) across a 6-speed freewheel (13-21).
Specifically, can a Shimano Dura-Ace FD-7400 shift correctly between a 40T outer chainring and a 34T inner chainring? It would be paired with a Shimano Dura-Ace 7401, which will be shifting (friction) across a 6-speed freewheel (13-21).
02-27-16, 12:53 PM
#2
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Should work great. Probably need to shorten the chain if it's in the original length intended for a 52/40 chain ring combo.
Set it up with the new chain rings and see if the chain looks saggy on the small/small combo. If so, take out a link pair and check it again. Still saggy? Take out another link pair. Even if you rarely use the small/small combo, it should be useable. With such a small difference up front, this should be easy-peasy.
Set it up with the new chain rings and see if the chain looks saggy on the small/small combo. If so, take out a link pair and check it again. Still saggy? Take out another link pair. Even if you rarely use the small/small combo, it should be useable. With such a small difference up front, this should be easy-peasy.
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● 1971 Grandis SL ● 1972 Lambert Grand Prix frankenbike ● 1972 Raleigh Super Course fixie ● 1973 Nishiki Semi-Pro ● 1979 Motobecane Grand Jubile ●1980 Apollo "Legnano" ● 1984 Peugeot Vagabond ● 1985 Shogun Prairie Breaker ● 1986 Merckx Super Corsa ● 1987 Schwinn Tempo ● 1988 Schwinn Voyageur ● 1989 Bottechia Team ADR replica ● 1990 Cannondale ST600 ● 1993 Technium RT600 ● 1996 Kona Lava Dome ●
● 1971 Grandis SL ● 1972 Lambert Grand Prix frankenbike ● 1972 Raleigh Super Course fixie ● 1973 Nishiki Semi-Pro ● 1979 Motobecane Grand Jubile ●1980 Apollo "Legnano" ● 1984 Peugeot Vagabond ● 1985 Shogun Prairie Breaker ● 1986 Merckx Super Corsa ● 1987 Schwinn Tempo ● 1988 Schwinn Voyageur ● 1989 Bottechia Team ADR replica ● 1990 Cannondale ST600 ● 1993 Technium RT600 ● 1996 Kona Lava Dome ●
Last edited by Lascauxcaveman; 02-27-16 at 12:58 PM.
02-27-16, 12:57 PM
#3
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02-27-16, 01:00 PM
#4
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maximum, yes. minimum, no
a 40t big ring is smaller than most of our inner (small) rings. even with a 13t rear cog, that's not a very big gear.
velobase shows your rd has a maximum chain wrap of 28 and max rear cog size of 26:
VeloBase.com - Component: Shimano RD-7401, Dura-Ace (7sp)
a 40t big ring is smaller than most of our inner (small) rings. even with a 13t rear cog, that's not a very big gear.
velobase shows your rd has a maximum chain wrap of 28 and max rear cog size of 26:
VeloBase.com - Component: Shimano RD-7401, Dura-Ace (7sp)
02-27-16, 01:06 PM
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New chains are nice (provided your freewheel/cassette cogs aren't all worn out). It'll probably come with 114 links and need to be shortened. And if you haven't got one already, you can get a cheap but functional chain breaker on the big auction site for $5, or spend a little more for a good one at your LBS.
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● 1971 Grandis SL ● 1972 Lambert Grand Prix frankenbike ● 1972 Raleigh Super Course fixie ● 1973 Nishiki Semi-Pro ● 1979 Motobecane Grand Jubile ●1980 Apollo "Legnano" ● 1984 Peugeot Vagabond ● 1985 Shogun Prairie Breaker ● 1986 Merckx Super Corsa ● 1987 Schwinn Tempo ● 1988 Schwinn Voyageur ● 1989 Bottechia Team ADR replica ● 1990 Cannondale ST600 ● 1993 Technium RT600 ● 1996 Kona Lava Dome ●
● 1971 Grandis SL ● 1972 Lambert Grand Prix frankenbike ● 1972 Raleigh Super Course fixie ● 1973 Nishiki Semi-Pro ● 1979 Motobecane Grand Jubile ●1980 Apollo "Legnano" ● 1984 Peugeot Vagabond ● 1985 Shogun Prairie Breaker ● 1986 Merckx Super Corsa ● 1987 Schwinn Tempo ● 1988 Schwinn Voyageur ● 1989 Bottechia Team ADR replica ● 1990 Cannondale ST600 ● 1993 Technium RT600 ● 1996 Kona Lava Dome ●
Last edited by Lascauxcaveman; 02-27-16 at 01:19 PM.
02-27-16, 01:08 PM
#6
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maximum, yes. minimum, no
a 40t big ring is smaller than most of our inner (small) rings. even with a 13t rear cog, that's not a very big gear.
velobase shows your rd has a maximum chain wrap of 28 and max rear cog size of 26:
VeloBase.com - Component: Shimano RD-7401, Dura-Ace (7sp)
a 40t big ring is smaller than most of our inner (small) rings. even with a 13t rear cog, that's not a very big gear.
velobase shows your rd has a maximum chain wrap of 28 and max rear cog size of 26:
VeloBase.com - Component: Shimano RD-7401, Dura-Ace (7sp)
02-27-16, 01:13 PM
#7
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I show that there will be less than 1/2 inch difference in size between the two chainrings. The inner cage may strike the inner ring before the shift to the large ring can be completed. You may have to raise the derailleur higher than the usual amount to stop this.
02-27-16, 01:13 PM
#8
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The only problem will be a somewhat non-ideal shape for the lower edge of the front derailleur, which is almost always curved to match the 52-tooth default size of the outer ring. However, my Peugeot works great with 45-42 up front and a 13-26 "ultra" 6 speed in back.
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Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069
"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069
02-27-16, 01:48 PM
#9
Living 'n Dying in ¾-Time
Thread Starter
Thank you! I appreciate the first-hand information... and the photo, too.
02-27-16, 01:50 PM
#10
Living 'n Dying in ¾-Time
Thread Starter
Well, forewarned is forearmed.
