Advertise on Bikeforums.net



User Tag List

Results 1 to 17 of 17
  1. #1
    cyclist/gearhead/cycli... moxfyre's Avatar
    Join Date
    Oct 2004
    Location
    DC / Maryland suburbs
    My Bikes
    Homebuilt tourer/commuter, modified-beyond-recognition 1990 Trek 1100, reasonably stock 2002-ish Gary Fisher Hoo Koo E Koo
    Posts
    4,182
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Rear derailer way too small :-(

    I finally finished reassembling the Nishiki frankenbike I've been working on. Most of the original components are of a good quality (SunTour, DiaCompe, Sugino), but one problem I've had is that the rear derailer is WAY TOO SMALL.

    With a double crank (50,40 -ish), and a 6 cog freewheel, only 3-4 of the 6 cogs can be used with each chainring, without binding the chain or having the derailer bend back so far it can't wrap it all up. And this is after a couple hours of derailer tweaking/chain resizing, etc.

    Has anyone ever seen a bike designed with such a woefully inadequate R Der? I'm thinking of getting a Shimano Sora 8 speed derailer from Nashbar, anyone know how well that'll work with friction shifters?
    My bikes | Linux and Python stuff | Photo gallery

    Sheldon Brown, I miss you. Thanks for the advice, ideas, humor, and infectious enthusiasm for everything bikes...

  2. #2
    Senior Member kerk's Avatar
    Join Date
    Jul 2003
    Location
    Cincinnati, Ohio
    My Bikes
    2011 Raleigh International, 3 - '73 World Voyageurs, Trek 700
    Posts
    889
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    You sure you have the high and low stop screws far enough out? Your rear der will surely shift to all cogs. Chain slack may be a problem, but I've never seen a rear der not handle a 6 speed freewheel.
    2011 Raleigh International
    '73 World Voyageurs -
    Proud owner of all three colors made! Orange, Blue , Yellow .

  3. #3
    Seņor Member USAZorro's Avatar
    Join Date
    Oct 2004
    Location
    Carlisle, PA
    My Bikes
    1954 Hetchins M.O., 1959 Viking Severn Valley, 1970 Raleigh Pro, 1972 Fuji "The Finest", 1974 Raleigh Superbe&Comp, 1976 Raleigh Team Pro, 1994 Trek 830 MTB, 2000 Bob Jackson Arrowhead, Unicycle
    Posts
    13,034
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by moxfyre
    I finally finished reassembling the Nishiki frankenbike I've been working on. Most of the original components are of a good quality (SunTour, DiaCompe, Sugino), but one problem I've had is that the rear derailer is WAY TOO SMALL.

    With a double crank (50,40 -ish), and a 6 cog freewheel, only 3-4 of the 6 cogs can be used with each chainring, without binding the chain or having the derailer bend back so far it can't wrap it all up. And this is after a couple hours of derailer tweaking/chain resizing, etc.

    Has anyone ever seen a bike designed with such a woefully inadequate R Der? I'm thinking of getting a Shimano Sora 8 speed derailer from Nashbar, anyone know how well that'll work with friction shifters?
    Your derailleur... Sun Tour? Which Model?
    The search for inner peace continues...

  4. #4
    cyclist/gearhead/cycli... moxfyre's Avatar
    Join Date
    Oct 2004
    Location
    DC / Maryland suburbs
    My Bikes
    Homebuilt tourer/commuter, modified-beyond-recognition 1990 Trek 1100, reasonably stock 2002-ish Gary Fisher Hoo Koo E Koo
    Posts
    4,182
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    The derailer is Sun Tour AR, I think it's from the early 80s, but the capacity isn't marked on it...

    And I don't think the limit screws are a problem because it has enough forward-and-backward motion to reach all the cogs. I also adjusted moved the wheel as far back in the dropout as possible (moving the cogs as far above the derailer as possible), and I adjusted the B-tension.
    My bikes | Linux and Python stuff | Photo gallery

    Sheldon Brown, I miss you. Thanks for the advice, ideas, humor, and infectious enthusiasm for everything bikes...

  5. #5
    Senior Member sydney's Avatar
    Join Date
    Jan 2004
    Posts
    9,428
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by kerk
    You sure you have the high and low stop screws far enough out? Your rear der will surely shift to all cogs. Chain slack may be a problem, but I've never seen a rear der not handle a 6 speed freewheel.
    There are plenty that might not handle a 33 or bigger cog that was common on 6 speed freewheels.

  6. #6
    Senior Member sydney's Avatar
    Join Date
    Jan 2004
    Posts
    9,428
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by moxfyre
    I finally finished reassembling the Nishiki frankenbike I've been working on. Most of the original components are of a good quality (SunTour, DiaCompe, Sugino), but one problem I've had is that the rear derailer is WAY TOO SMALL.

    With a double crank (50,40 -ish), and a 6 cog freewheel, only 3-4 of the 6 cogs can be used with each chainring, without binding the chain or having the derailer bend back so far it can't wrap it all up. And this is after a couple hours of derailer tweaking/chain resizing, etc.

    Has anyone ever seen a bike designed with such a woefully inadequate R Der? I'm thinking of getting a Shimano Sora 8 speed derailer from Nashbar, anyone know how well that'll work with friction shifters?
    What's the tooth count on the biggest and smallest rear cogs, and the tooth count on the big andsmall rings? A sora 8 speed will work with friction, but won't work if your big cog or wrap requirement exceeds it's capacity.sounds to me like you are currently exceeding the wrap capacity of your RD.

  7. #7
    Seņor Member USAZorro's Avatar
    Join Date
    Oct 2004
    Location
    Carlisle, PA
    My Bikes
    1954 Hetchins M.O., 1959 Viking Severn Valley, 1970 Raleigh Pro, 1972 Fuji "The Finest", 1974 Raleigh Superbe&Comp, 1976 Raleigh Team Pro, 1994 Trek 830 MTB, 2000 Bob Jackson Arrowhead, Unicycle
    Posts
    13,034
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by sydney
    What's the tooth count on the biggest and smallest rear cogs, and the tooth count on the big andsmall rings? A sora 8 speed will work with friction, but won't work if your big cog or wrap requirement exceeds it's capacity.sounds to me like you are currently exceeding the wrap capacity of your RD.

    Actually, we ought to ask which cogs it isn't reaching. It could be size, spring tension, dishing, or a bad derailleur. I found a Nishiki 12 speed (Marina) a few weeks ago with the same derailleur. It was way too big for me to extensively test ride, but I noted the rear derailleur wasn't hitting all the gears. I passed it off to just needing adjustment, but maybe that's not it.
    The search for inner peace continues...

  8. #8
    Seņor Member USAZorro's Avatar
    Join Date
    Oct 2004
    Location
    Carlisle, PA
    My Bikes
    1954 Hetchins M.O., 1959 Viking Severn Valley, 1970 Raleigh Pro, 1972 Fuji "The Finest", 1974 Raleigh Superbe&Comp, 1976 Raleigh Team Pro, 1994 Trek 830 MTB, 2000 Bob Jackson Arrowhead, Unicycle
    Posts
    13,034
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I had another though there. Where did you mount the derailleur? Is it behind the axle in the dropout, or below?
    The search for inner peace continues...

  9. #9
    cyclist/gearhead/cycli... moxfyre's Avatar
    Join Date
    Oct 2004
    Location
    DC / Maryland suburbs
    My Bikes
    Homebuilt tourer/commuter, modified-beyond-recognition 1990 Trek 1100, reasonably stock 2002-ish Gary Fisher Hoo Koo E Koo
    Posts
    4,182
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    So, with the large chainring, it hits the 4 smallest gears, but the derailer gets sucked up against the cogs if I try to go to the two largest. With the small chainring, it hits the 4 largest gears, but can't wrap up enough for the two smallest :-( I'll count the teeth when I get home this evening!!
    My bikes | Linux and Python stuff | Photo gallery

    Sheldon Brown, I miss you. Thanks for the advice, ideas, humor, and infectious enthusiasm for everything bikes...

  10. #10
    Senior Member
    Join Date
    Nov 2004
    Posts
    9,998
    Mentioned
    3 Post(s)
    Tagged
    1 Thread(s)
    It is most likely a case of inadequate derailleur capacity, as Sidney suggests. However, it could also be insufficient spring tension for the cage pivot as USAZorro suggests. In the later scenario, I have seen cases where owners have shortened the chain trying to compensate for tension problems, resulting in a binding situation in the large/large combination and slack in the small/small combination. Ideally one should not be riding in these combinations, due to the severe chain angle, however the bicycle, as originally manufactured, would surely have handled these combinations without the chain tension problems you described. If not, there would have been huge potential for lawsuits.

    FYI, the SunTour AR came in long and medium cage combinations. The medium cage (model RD-4200 - should be stamped on back) was rated for a 28T maximum cog and a 30T total capacitiy. The long cage RD-4400 was rated for a 30T maximum cog and 34T toal capacity. Once we know the derailleur model number and the sizes of the chainrings and cogs, we will have a much better idea of the problem and how to solve it.

  11. #11
    feros ferio John E's Avatar
    Join Date
    Jul 2000
    Location
    www.ci.encinitas.ca.us
    My Bikes
    1959 Capo; 1980 Peugeot PKN-10; 1981 Bianchi; 1988 Schwinn KOM-10;
    Posts
    14,357
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by moxfyre
    So, with the large chainring, it hits the 4 smallest gears, but the derailer gets sucked up against the cogs if I try to go to the two largest. With the small chainring, it hits the 4 largest gears, but can't wrap up enough for the two smallest :-( I'll count the teeth when I get home this evening!!
    Yes, please do. If you have a short-cage derailleur, you cannot run more than 24, perhaps 26, teeth on your largest rear cog. The key is the pivot point of the cage. If the pivot point is lined up with the jockey (upper) pulley, you have a wide-range derailleur, which should be able to handle 13-32 or even 34 teeth, even with a 10-tooth drop in front. If the pivot falls between the two pulleys, you have a racing or narrow-range derailleur.

    I have a tight-range SunTour Cyclone II on my PKN-10. It handles my 48-45-34 / 13-15-17-19-21-23 half-step-plus-Grannie combination nicely, but it's near its wrap limit.
    "Early to bed, early to rise. Work like hell, and advertise." -- George Stahlman
    Capo [dschaw'-poe]: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger, S/N 42624
    Peugeot: 1970 UO-8, S/N 0010468
    Bianchi: 1981 Campione d'Italia, S/N 1.M9914
    Schwinn: 1988 Project KOM-10, S/N F804069

  12. #12
    Senior Member sydney's Avatar
    Join Date
    Jan 2004
    Posts
    9,428
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by USAZorro
    Actually, we ought to ask which cogs it isn't reaching. It could be size, spring tension, dishing, or a bad derailleur. I found a Nishiki 12 speed (Marina) a few weeks ago with the same derailleur. It was way too big for me to extensively test ride, but I noted the rear derailleur wasn't hitting all the gears. I passed it off to just needing adjustment, but maybe that's not it.
    No the question cannot be answered without knowing the chainring and cog sizes! Now if we knew the RD and chainset/freewheel were all original to the bike,we could THEN assume it was not a component compatibility issue.

  13. #13
    Senior Member sydney's Avatar
    Join Date
    Jan 2004
    Posts
    9,428
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by John E
    Yes, please do. If you have a short-cage derailleur, you cannot run more than 24, perhaps 26, teeth on your largest rear cog.
    that is just not always true either.

  14. #14
    Senior Member sydney's Avatar
    Join Date
    Jan 2004
    Posts
    9,428
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by John E
    Yes, please do. If you have a short-cage derailleur, you cannot run more than 24, perhaps 26, teeth on your largest rear cog. The key is the pivot point of the cage. If the pivot point is lined up with the jockey (upper) pulley, you have a wide-range derailleur, which should be able to handle 13-32 or even 34 teeth, even with a 10-tooth drop in front. If the pivot falls between the two pulleys, you have a racing or narrow-range deerailer.
    I think this depends on the make and vintage of derailer.It works for some old suntour stuff I have but doesn't apply to a newer shimano stuff. There is more to it than cage length too,as that is mostly about wrap. Parallelogram geometry is a serious part of ability to shift a big cog.

  15. #15
    cyclist/gearhead/cycli... moxfyre's Avatar
    Join Date
    Oct 2004
    Location
    DC / Maryland suburbs
    My Bikes
    Homebuilt tourer/commuter, modified-beyond-recognition 1990 Trek 1100, reasonably stock 2002-ish Gary Fisher Hoo Koo E Koo
    Posts
    4,182
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    John E, Sydney, thanks for your help. It was in fact the medium cage model and I think I had set the spring tension too low when I cleaned the derailer. So to save time (I'm giving this to my gf tonight), I slapped an Altus long cage rder on there, out of the parts box. Doesn't quite match the other chrome components, but it shifts quite well...

    Here's a photo of the finished Frankenbike, including Baby Blue paint job, which doesn't look half bad considering how I butchered it. I need to get matching handlebar tape eventually too. I think the Sugino cranks look real awesome, would love to find another set for my own use.
    My bikes | Linux and Python stuff | Photo gallery

    Sheldon Brown, I miss you. Thanks for the advice, ideas, humor, and infectious enthusiasm for everything bikes...

  16. #16
    Seņor Member USAZorro's Avatar
    Join Date
    Oct 2004
    Location
    Carlisle, PA
    My Bikes
    1954 Hetchins M.O., 1959 Viking Severn Valley, 1970 Raleigh Pro, 1972 Fuji "The Finest", 1974 Raleigh Superbe&Comp, 1976 Raleigh Team Pro, 1994 Trek 830 MTB, 2000 Bob Jackson Arrowhead, Unicycle
    Posts
    13,034
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Very well done Moxfire. The Nishiki I rescued has the exact same derailleur, and a 13-27 six speed Suntour freewheel. If I had the larger one, I would have offered you a trade. If you're interested in the freewheel, let me know - I doubt I'll be using it.
    The search for inner peace continues...

  17. #17
    cyclist/gearhead/cycli... moxfyre's Avatar
    Join Date
    Oct 2004
    Location
    DC / Maryland suburbs
    My Bikes
    Homebuilt tourer/commuter, modified-beyond-recognition 1990 Trek 1100, reasonably stock 2002-ish Gary Fisher Hoo Koo E Koo
    Posts
    4,182
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Hey, thanks! My girlfriend is gonna be riding it and I don't think she cares too much about gear ratios
    My bikes | Linux and Python stuff | Photo gallery

    Sheldon Brown, I miss you. Thanks for the advice, ideas, humor, and infectious enthusiasm for everything bikes...

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •