BCD of Nervar crankset?
06-17-16, 07:50 PM
#1
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BCD of Nervar crankset?
Anybody know offhand what the BCD of my Nervar 1020 crankset would be? (It's on a 1983 Grand Jubile). I know there's a way to calculate it, but I don't trust my math skills! I believe the older Nervar cranks (like the Star) were 128 BCD but I can't find any info on the more recent ones.
06-17-16, 08:34 PM
#2
curmudgineer
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122mm is probable. There is a way to calculate the BCD from the centre to centre distance of adjacent holes, but I don't have it memorized. If you're still stuck by this time tomorrow I'll find it and post it.
06-17-16, 10:57 PM
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Anybody know offhand what the BCD of my Nervar 1020 crankset would be? (It's on a 1983 Grand Jubile). I know there's a way to calculate it, but I don't trust my math skills! I believe the older Nervar cranks (like the Star) were 128 BCD but I can't find any info on the more recent ones.
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06-18-16, 06:38 AM
#4
feros ferio
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128. Odd duck in the BCD world, hard to find chain rings for. ...
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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
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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
06-18-16, 11:41 AM
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Try looking it up on velobase.com.
06-18-16, 05:37 PM
#7
curmudgineer
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The general method is as follows.
- get the angle between the chainring bolts and divide by 2. E.g. the angle between 5 equally spaced bolts is 72 degrees. Half of this is 36 degrees.
- get the sine of this angle. The sine of 36 degrees is approximately 0.588
Measure the distance between the centres of adjacent chainring bolts.
Divide this distance by the sine of the angle between the adjacent bolts. The result is the diameter of the bolt circle.
- get the angle between the chainring bolts and divide by 2. E.g. the angle between 5 equally spaced bolts is 72 degrees. Half of this is 36 degrees.
- get the sine of this angle. The sine of 36 degrees is approximately 0.588
Measure the distance between the centres of adjacent chainring bolts.
Divide this distance by the sine of the angle between the adjacent bolts. The result is the diameter of the bolt circle.
06-18-16, 07:38 PM
#8
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I like an online BCD calculator better. Just need to measure adjacent bolt hole centers (as accurately as possible) and use the proper mulitiplier for however many bolts there are. Obviously, your measurements in the field may be a tiny bit off, so you have to take a look at what known BCDs apply to chainrings available to old crank sets, and see which one you're close to. Of course Sheldon Brown has a crib sheet that calls most of them out by name.
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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; 06-18-16 at 07:45 PM.
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