Advertise on Bikeforums.net



User Tag List

Results 1 to 12 of 12
  1. #1
    Klaatu barada nikto cascade168's Avatar
    Join Date
    Sep 2004
    Location
    Southern NH
    Posts
    1,453
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I got a mint 7spd (105 rear hub[126mm] with HG cassette) given to me. It's a mid '80s Japanese bike, I believe. Someone spray painted it "anonymous blue", so the heritage is unknown. But, it's lovely lugged steel and in nearly perfect condition. The only problem with the bike is that the RD took a major hit somewhere along the line and the pivot points are not "solid". Can I just install a new 105 RD(9spd) and have it index properly?

    Does the RD really care about the # of indexed speeds? How do you gauge/measure this capability/capacity? What's the pertinent metric/s?

    Fire away ;-)
    Last edited by cascade168; 11-17-05 at 10:57 PM.
    "Work is the curse of the drinking class."
    - Oscar Wilde

  2. #2
    barnfullagts
    Join Date
    Oct 2005
    Location
    WI
    My Bikes
    GT BI Ti/BI Steel - Edge Ti and Steel Xizang Ti and Psyclone Steel
    Posts
    615
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    yes

  3. #3
    Senior Member (Retired) gmason's Avatar
    Join Date
    Sep 2001
    Location
    Great North Woods
    My Bikes
    Vittorio, Centaur triple; Casati Laser Piu, Chorus Triple.
    Posts
    2,671
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by cascade168
    Does the RD really care about the # of indexed speeds? How do you gauge/measure this capability/capacity? What's the pertinent metric/s?
    The RD is essentially a free travelling parallelogram with an internal spring moving it in one direction and the cable (therefore the shifter) moving it in the other. The "indexing" is a function of how much cable travel occurs based upon the shifter's movement of it.

    So, the shifter determines the travel between cogs, and therefore must be matched to the cassette. The RD is essentially along for the ride and only follows orders.

    The only limitation I can think of would be trying to use a RD intended for a small number of cogs whose travel may be limited too much to travel over the width of a newer standard cassette. In other words, a 126mm RD on a 130mm cassette. I am not sure if that is, in fact, a practical limitation, but probably easily guarded against in any case - use a newer RD on an older cassette.

  4. #4
    Senior Member sydney's Avatar
    Join Date
    Jan 2004
    Posts
    9,428
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by gmason
    The RD is essentially a free travelling parallelogram with an internal spring moving it in one direction and the cable (therefore the shifter) moving it in the other. The "indexing" is a function of how much cable travel occurs based upon the shifter's movement of it.

    So, the shifter determines the travel between cogs, and therefore must be matched to the cassette. The RD is essentially along for the ride and only follows orders.
    Well actually,the RD throw ratio does have to match the shifter, in index systems. Then it can follow orders properly.That's why a sram esp RD is not compatible with simano but a sram mrx RD is.Also the reason for much campy shimano incompatibality.

  5. #5
    Senior Member (Retired) gmason's Avatar
    Join Date
    Sep 2001
    Location
    Great North Woods
    My Bikes
    Vittorio, Centaur triple; Casati Laser Piu, Chorus Triple.
    Posts
    2,671
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by sydney
    Well actually, ...
    I figured I would learn where my mistakes were from you sydney.

  6. #6
    Gone, but not forgotten Sheldon Brown's Avatar
    Join Date
    Jul 2002
    Location
    Newtonville, Massachusetts
    My Bikes
    See: http://sheldonbrown.org/bicycles
    Posts
    2,301
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by sydney
    Well actually,the RD throw ratio does have to match the shifter, in index systems. Then it can follow orders properly.That's why a sram esp RD is not compatible with simano but a sram mrx RD is.Also the reason for much campy shimano incompatibality.
    That's true but not to the point in this issue.

    The rear derailer has to match the brand of shifter.

    Within brands there are a couple of incompatibilities:
    • Pre-1997 Dura-Ace vs. all other Shimano
    • Sram ESP vs. Sram Shimano compatible


    However, within a given system the number of speeds does not matter to the derailer. The O.P. can use any Shimano derailer on his or her bike.

    Sheldon "Lets Not Make It Seem Harder Than It Is" Brown
    Code:
    +----------------------------------------------------+
    |     A little inaccuracy sometimes saves tons of    |
    |    explanation.  --H.H.Munro ("Saki")(1870-1916)   |
    +----------------------------------------------------+
    [COLOR=blue][CENTER][b]Harris Cyclery, West Newton, Massachusetts[/b]
    Phone 617-244-9772, FAX 617-244-1041
    [URL= http://harriscyclery.com] http://harriscyclery.com[/URL]
    Hard-to-find parts shipped Worldwide
    [URL=http://captainbike.com]http://captainbike.com[/URL]
    Useful articles about bicycles and cycling
    [URL=http://sheldonbrown.com]http://sheldonbrown.com[/URL] [/CENTER] [/COLOR]

  7. #7
    Senior Member sydney's Avatar
    Join Date
    Jan 2004
    Posts
    9,428
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Sheldon Brown
    That's true but not to the point in this issue.

    The rear derailer has to match the brand of shifter.

    Within brands there are a couple of incompatibilities:
    • Pre-1997 Dura-Ace vs. all other Shimano
    • Sram ESP vs. Sram Shimano compatible


    However, within a given system the number of speeds does not matter to the derailer. The O.P. can use any Shimano derailer on his or her bike.

    Sheldon "Lets Not Make It Seem Harder Than It Is" Brown
    Code:
    +----------------------------------------------------+
    |     A little inaccuracy sometimes saves tons of    |
    |    explanation.  --H.H.Munro ("Saki")(1870-1916)   |
    +----------------------------------------------------+
    Shouldn't that be any SIS shimano RD in an index system? My commment wasn't directed to the O.P., as yes was the correct, short, simple answer. Long answers are often needed to clear up misconceptions. Thanks for the imput.'...... sydney "just tellin it like it is" no carpet smoke
    Last edited by sydney; 11-18-05 at 09:46 AM.

  8. #8
    Gone, but not forgotten Sheldon Brown's Avatar
    Join Date
    Jul 2002
    Location
    Newtonville, Massachusetts
    My Bikes
    See: http://sheldonbrown.org/bicycles
    Posts
    2,301
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by sydney
    Shouldn't that be any SIS shimano RD in an index system? My commment wasn't directed to the O.P., as yes was the correct, short, simple answer. Long answers are often needed to clear up misconceptions. Thanks for the imput.'...... sydney "just tellin it like it is" no carpet smoke
    All Shimano rear derailers made since about 1987 are SIS. As to the index issue, this is _only_ an issue with index systems...friction basically works with everything.

    (Yes, I know the old Benelux coil spring derailers from the '50s needed a lever with more travel...) ;-)

    Sheldon "How Far Back Do We Need To Go?" Brown
    Code:
    +-------------------------------------------+
    |   Any smoothly functioning technology     |
    |   will have the appearance of magic.      |
    |                     --Arthur C. Clarke    |
    +-------------------------------------------+
    [COLOR=blue][CENTER][b]Harris Cyclery, West Newton, Massachusetts[/b]
    Phone 617-244-9772, FAX 617-244-1041
    [URL= http://harriscyclery.com] http://harriscyclery.com[/URL]
    Hard-to-find parts shipped Worldwide
    [URL=http://captainbike.com]http://captainbike.com[/URL]
    Useful articles about bicycles and cycling
    [URL=http://sheldonbrown.com]http://sheldonbrown.com[/URL] [/CENTER] [/COLOR]

  9. #9
    Klaatu barada nikto cascade168's Avatar
    Join Date
    Sep 2004
    Location
    Southern NH
    Posts
    1,453
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thank you all for your replies. I see now that I did not mention the shifters I am planning to use. I have some 8spd Ultegra barcons. So, if I understand correctly, I am good to go but I'll have one dead click.

    So, it was apparent to me that for some given amount of pull on the cable (in length) you get a corresponding side-to-side change (in width) on the derailleur parellelogram. Since both of these movements are distance measurements, they can be gauged and the actual ratio can be determined. As I now understand (thank you gmason!), this relationship is linear and is what you are calling "throw ratio".

    Apparently different manufacturers use different throw ratios, but not always. And, some manufacturers may have different throw ratios within their own product line.

    Ok, so last two questions:

    Is there a straightforward way to make the measurements and determine throw ratio? (I am thinking that this is easier said than done).

    Is there some reference where someone has already done the work and it's all recorded? or, do we all have to rely on our good friend Sheldon for the specifics?
    "Work is the curse of the drinking class."
    - Oscar Wilde

  10. #10
    Senior Member sydney's Avatar
    Join Date
    Jan 2004
    Posts
    9,428
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Sheldon Brown
    All Shimano rear derailers made since about 1987 are SIS. As to the index issue, this is _only_ an issue with index systems...friction basically works with everything.

    (Yes, I know the old Benelux coil spring derailers from the '50s needed a lever with more travel...) ;-)

    Sheldon "How Far Back Do We Need To Go?" Brown
    Code:
    +-------------------------------------------+
    |   Any smoothly functioning technology     |
    |   will have the appearance of magic.      |
    |                     --Arthur C. Clarke    |
    +-------------------------------------------+
    Probably nit picking,but I was thinking 1985. sydney "got a box full of old pre index shimano RD that wouldn't work" the pack rat .

  11. #11
    Gone, but not forgotten Sheldon Brown's Avatar
    Join Date
    Jul 2002
    Location
    Newtonville, Massachusetts
    My Bikes
    See: http://sheldonbrown.org/bicycles
    Posts
    2,301
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by cascade168
    Thank you all for your replies. I see now that I did not mention the shifters I am planning to use. I have some 8spd Ultegra barcons. So, if I understand correctly, I am good to go but I'll have one dead click.
    In Shimano setups, the spacing is slightly different between 7- and 8-speed cassettes, but generally it's close enough to let you use 8-speed shifters with a 7-speed system.

    There won't be any extra click if the derailer's limit screws are adjusted properly.


    Quote Originally Posted by cascade168
    So, it was apparent to me that for some given amount of pull on the cable (in length) you get a corresponding side-to-side change (in width) on the derailleur parellelogram. Since both of these movements are distance measurements, they can be gauged and the actual ratio can be determined. As I now understand (thank you gmason!), this relationship is linear and is what you are calling "throw ratio".

    Apparently different manufacturers use different throw ratios, but not always. And, some manufacturers may have different throw ratios within their own product line.

    Ok, so last two questions:

    Is there a straightforward way to make the measurements and determine throw ratio? (I am thinking that this is easier said than done).
    It's not that easy to measure, but there is generally no need to measure it in practice, just match the brand of derailer to the brand of shifter, and the number of shifter clicks to the number of sprockets on the cluster.


    Quote Originally Posted by cascade168
    Is there some reference where someone has already done the work and it's all recorded? or, do we all have to rely on our good friend Sheldon for the specifics?
    See my latest article: http://sheldonbrown.com/speeds

    Sheldon "Numbers" Brown
    Code:
    +--------------------------------------------------------+
    |  As far as the laws of mathematics refer to reality,   |
    |  they are not certain; and as far as they are certain, |
    |  they do not refer to reality.      --Albert Einstein  |
    +--------------------------------------------------------+
    [COLOR=blue][CENTER][b]Harris Cyclery, West Newton, Massachusetts[/b]
    Phone 617-244-9772, FAX 617-244-1041
    [URL= http://harriscyclery.com] http://harriscyclery.com[/URL]
    Hard-to-find parts shipped Worldwide
    [URL=http://captainbike.com]http://captainbike.com[/URL]
    Useful articles about bicycles and cycling
    [URL=http://sheldonbrown.com]http://sheldonbrown.com[/URL] [/CENTER] [/COLOR]

  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 cascade168
    Thank you all for your replies. I see now that I did not mention the shifters I am planning to use. I have some 8spd Ultegra barcons. So, if I understand correctly, I am good to go but I'll have one dead click.

    So, it was apparent to me that for some given amount of pull on the cable (in length) you get a corresponding side-to-side change (in width) on the derailleur parellelogram. Since both of these movements are distance measurements, they can be gauged and the actual ratio can be determined. As I now understand (thank you gmason!), this relationship is linear and is what you are calling "throw ratio".

    Apparently different manufacturers use different throw ratios, but not always. And, some manufacturers may have different throw ratios within their own product line.

    Ok, so last two questions:

    Is there a straightforward way to make the measurements and determine throw ratio? (I am thinking that this is easier said than done).

    Is there some reference where someone has already done the work and it's all recorded? or, do we all have to rely on our good friend Sheldon for the specifics?
    The simple answer is that the 8 speed ultegra barcons are compatible with a '9 speed' 105 RD with respect to the mechanics involved. Shimano 7 speed cog spacing is 5mm and 8 is 4.8mm. That is close enough that what you propose to do usually works.I've done it. Others say is doesn't work well enough for them.YMMV.

Posting Permissions

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