How to find out chain wrap capacity?
#1
Junior Member
Thread Starter
Join Date: Sep 2020
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Liked 0 Times
in
0 Posts
How to find out chain wrap capacity?
[EDIT: How to find out rear derailer's MAX chain wrap capacity?]
I want to convert my Raleigh Olympian from 52/40 teeth chainrings to 50/34 teeth chainrings. Poking through this forum taught me that I need to somehow make sure that my rear derailleur will be able to handle the extra 4 teeth chain wrap capacity ((50-34) - (52-40)=4). How do I know if my rear derailleur will be able to handle this difference? Velobase.com has my rear derailleur but the entry for max chain wrap has been left blank. Can you tell me if my conversion will be successful?
Components:
Front deraulier: "SUNTOUR 7" written on it.
Rear derailleur: "SUNTOUR SEVEN" written on it. The exact model is SunTour Seven 1b.
Current chainrings: 52/40
Future intended chainrings: 50/34
Current cogset: 6 cogs 30/14 teeth (yes they are 6 and not 7)
Current chain wrap capacity = 52-40+30-14 = 28
Future intended chain wrap capacity = 50-34+30-14 = 32
2 related but less important questions:
1. Where can I find a 50/34 crankset in vintage-looking grey/silver color? Did vintage bikes even have those? Amazon and Ebay are only showing black colors.
2. When they designed my Raleigh Olympian back in the day (~1984), who was it targeted towards? Did they think that people wouldn't do some serious climbing on it? The reason I want a smaller small chainring is that climbs become grueling sometimes. In my backyard where there is a road called "Old La Honda", the average grade is 7.5% with max grade = 18% inside switchbacks. Those 18% regions have me out of the saddle and if I am touring with large panniers, I can only climb those regions if I am weaving.
I want to convert my Raleigh Olympian from 52/40 teeth chainrings to 50/34 teeth chainrings. Poking through this forum taught me that I need to somehow make sure that my rear derailleur will be able to handle the extra 4 teeth chain wrap capacity ((50-34) - (52-40)=4). How do I know if my rear derailleur will be able to handle this difference? Velobase.com has my rear derailleur but the entry for max chain wrap has been left blank. Can you tell me if my conversion will be successful?
Components:
Front deraulier: "SUNTOUR 7" written on it.
Rear derailleur: "SUNTOUR SEVEN" written on it. The exact model is SunTour Seven 1b.
Current chainrings: 52/40
Future intended chainrings: 50/34
Current cogset: 6 cogs 30/14 teeth (yes they are 6 and not 7)
Current chain wrap capacity = 52-40+30-14 = 28
Future intended chain wrap capacity = 50-34+30-14 = 32
2 related but less important questions:
1. Where can I find a 50/34 crankset in vintage-looking grey/silver color? Did vintage bikes even have those? Amazon and Ebay are only showing black colors.
2. When they designed my Raleigh Olympian back in the day (~1984), who was it targeted towards? Did they think that people wouldn't do some serious climbing on it? The reason I want a smaller small chainring is that climbs become grueling sometimes. In my backyard where there is a road called "Old La Honda", the average grade is 7.5% with max grade = 18% inside switchbacks. Those 18% regions have me out of the saddle and if I am touring with large panniers, I can only climb those regions if I am weaving.
Last edited by kkraoj; 09-08-20 at 09:51 PM.
#2
Senior Member
You can calculate your chain wrap capacity by subtracting the number of teeth on your largest front chainring from the number of teeth on your smallest front chainring, doing the same with the gears on your rear cassette, then adding the two values. So necessary chain wrap capacity on a bike with a 44-tooth big ring, 22-tooth small ring, and 11-34-tooth cassette, would work out like this:
(44-22) + (34-11) = 45
Not my words but it came from this website chain wrap capacity ? CanooterValve
(44-22) + (34-11) = 45
Not my words but it came from this website chain wrap capacity ? CanooterValve
#3
Junior Member
Thread Starter
Join Date: Sep 2020
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Liked 0 Times
in
0 Posts
Thanks for the response! I actually got the terminology wrong. I don't want to calculate chain wrap capacity. I know it for my gears. I only want to know if my rear derailer can handle an additional 4 chain wrap capacity.
#4
Senior Member
https://velobase.com/
#6
Junior Member
Thread Starter
Join Date: Sep 2020
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Liked 0 Times
in
0 Posts
Thanks again for the responses. Velobase.com looks like an amazing resource! I found my rear derailleur on the website. It is actually Suntour seven 1b. But the entry in front of "Max chain wrap" is blank.
#7
Senior Member
Join Date: Jun 2006
Posts: 20,305
Mentioned: 130 Post(s)
Tagged: 0 Thread(s)
Quoted: 3464 Post(s)
Liked 2,829 Times
in
1,995 Posts
The GT series have the long cages, with that, probably not a problem- with a standard cage-
I don’t think so.
I don’t think so.
#8
Senior Member
Join Date: Oct 2014
Location: Portland, OR
Posts: 12,905
Bikes: (2) ti TiCycles, 2007 w/ triple and 2011 fixed, 1979 Peter Mooney, ~1983 Trek 420 now fixed and ~1973 Raleigh Carlton Competition gravel grinder
Mentioned: 129 Post(s)
Tagged: 0 Thread(s)
Quoted: 4806 Post(s)
Liked 3,928 Times
in
2,553 Posts
Another approach - try what you've go. Change the chainring. Shift into small-small. Does that work? I'm guessing the derailleur cage will be roughly straight back and unable to get full tenison of the chain. The chain may be hitting itself. But neither of these is a deal breaker if it doesn't bother the matter between your ears. It is a gear that you shouldn't be using very much. Working but meeting nobody's idea of kosher is OK.
If it doesn't, there may be other easy options. First, if you cannot make that derailleur work, it will probably be because it is a medium cage, not a long cage. SunTour cages could be swapped. I'm sure there are tutorials on line and if not, we can help you. I used to tour and race on the same Cyclone, just different cages. Cyclone - a lot lighter and sexier than the 7 and not interchangeable but no different in concept. You may be able to go to a coop and find a 7 with a longer cage. (It can be crashed and have a broken upper body. I used to rebuild my Cyclones after crashes and wear by buying crashed derailleurs from bike shop wrecked parts bins for $5 with the half I needed intact. Kept a Cyclone going for about 20 years and an absurd amount of miles doing that.
Ben
If it doesn't, there may be other easy options. First, if you cannot make that derailleur work, it will probably be because it is a medium cage, not a long cage. SunTour cages could be swapped. I'm sure there are tutorials on line and if not, we can help you. I used to tour and race on the same Cyclone, just different cages. Cyclone - a lot lighter and sexier than the 7 and not interchangeable but no different in concept. You may be able to go to a coop and find a 7 with a longer cage. (It can be crashed and have a broken upper body. I used to rebuild my Cyclones after crashes and wear by buying crashed derailleurs from bike shop wrecked parts bins for $5 with the half I needed intact. Kept a Cyclone going for about 20 years and an absurd amount of miles doing that.
Ben
Likes For 79pmooney:
#9
Senior Member
Join Date: Nov 2011
Location: Port Angeles, WA
Posts: 7,922
Bikes: A green one, "Ragleigh," or something.
Mentioned: 194 Post(s)
Tagged: 0 Thread(s)
Quoted: 1627 Post(s)
Liked 630 Times
in
356 Posts
Another approach - try what you've go. Change the chainring. Shift into small-small. Does that work? I'm guessing the derailleur cage will be roughly straight back and unable to get full tenison of the chain. The chain may be hitting itself. But neither of these is a deal breaker if it doesn't bother the matter between your ears. It is a gear that you shouldn't be using very much. Working but meeting nobody's idea of kosher is OK.
...
Ben
...
Ben
"OK, let's see what this little sucker can handle..."
__________________
● 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 ●
#10
Senior Member
Join Date: May 2013
Location: Pacific Northwest
Posts: 1,990
Bikes: ‘87 Marinoni SLX Sports Tourer, ‘79 Miyata 912 by Gugificazione
Mentioned: 166 Post(s)
Tagged: 0 Thread(s)
Quoted: 500 Post(s)
Liked 466 Times
in
256 Posts
Look for 110 mm BCD cranks, often listed as 110/74 (74mm being the granny ring bolt circle), but you don’t have to put on a granny ring. There are plenty of those in silver. Excellent high quality C&V cranks include Sugino AT (actually the original 110/74), many Shimano models, Specialized “flag”, and lots more. Sugino still makes one as their XD600 model, although that one looks a bit less C&V.
Last edited by Dfrost; 09-09-20 at 01:55 AM.
#11
feros ferio
Join Date: Jul 2000
Location: www.ci.encinitas.ca.us
Posts: 21,796
Bikes: 1959 Capo Modell Campagnolo; 1960 Capo Sieger (2); 1962 Carlton Franco Suisse; 1970 Peugeot UO-8; 1982 Bianchi Campione d'Italia; 1988 Schwinn Project KOM-10;
Mentioned: 44 Post(s)
Tagged: 0 Thread(s)
Quoted: 1392 Post(s)
Liked 1,324 Times
in
836 Posts
"Old La Honda Rd." sounds like a segment of my first century-long (double metric, actually) back in the early 1970s, with my cousin, who lived in Los Altos at the time. I see what you mean about wanting some lower gears.
Any long cage SunTour rear derailleur should have no trouble with your proposed gearing scheme.
Any long cage SunTour rear derailleur should have no trouble with your proposed gearing scheme.
__________________
"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
"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
#12
working on my sandal tan
Join Date: Aug 2011
Location: CID
Posts: 22,629
Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers), All-City Space Horse (hers)
Mentioned: 98 Post(s)
Tagged: 0 Thread(s)
Quoted: 3871 Post(s)
Liked 2,568 Times
in
1,579 Posts
Oh gotcha... Look on velobase and if you can find your derailleur, it should have specs.
VeloBase.com
VeloBase.com