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  1. #1
    Sir Fallalot wroomwroomoops's Avatar
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    Which track sprockets (cogs) have ISO, and which have english threading?

    I ask this, 'cause I have sprockets from various manufacturers, and have become aware, recently, thatthere is a very slight difference between ISO and english threading, on these sprockets, and that it is NOT advised to go back and forth with different-threaded sprockets on a track hub. I.E., if you put an ISO-threaded sprocket on the hub, then replace it only with an ISO threaded sprocket. And viceversa, for english threaded track sprocket.

    I only know for certain that Surly sprockets have ISO threading. But what about EAI? Milwaukee? Shimano? Cobra? Phil Wood? (OK, I don't have any Phil Wood sprockets, but bear with me...) What about those "German" sprockets?

    There must be someone who made a little database of sprockets.


    P.S. I call them sprockets, because that's what they, technicallly, are. Cogs engage other toothed wheels, while sprockets engage chains.

  2. #2
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    Sheldon Brown is the authority on fixed gear and similar bikes so he is the likely candidate to have this info.

    I BELIEVE that ISO (aka Italian) threading has a 55 thread angle while English is 60 but the diameter and thread pitch are otherwise identical.

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    ISO (International Standards Organization) is not Italian threading. For track cogs and freewheels, there is no difference between ISO and British threading. From Sheldon's site:

    Most ISO standards are compatible with British standards. These standards include:

    1" x 24 tpi headset thread
    1" (25.4 mm) handlebar/stem clamp diameter
    1.375" x 24 tpi bottom bracket thread (left-hand on the fixed cup)
    1.375" x 24 tpi freewheel thread
    56 TPI spoke thread
    1 mm axle thread
    Last edited by Trakhak; 01-28-07 at 08:38 AM.

  4. #4
    Sir Fallalot wroomwroomoops's Avatar
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    HillRider, you are quite right, Sheldon, if anyone, might have this information.
    Last edited by wroomwroomoops; 01-28-07 at 12:30 PM.

  5. #5
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    You're confusing Italian threading with ISO threading (as did Hillrider in his post above). For track cog or freewheel threading, the ISO standard is not just compatible with British threading: ISO adopted British threading dimensions for their rear hub threading standard. "Compatible" in this case means identical. There is no difference between ISO freewheel/track cog threading and and British freewheel/track cog threading.
    Last edited by Trakhak; 01-28-07 at 11:31 AM.

  6. #6
    Gone, but not forgotten Sheldon Brown's Avatar
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    Quote Originally Posted by Trakhak
    You're confusing Italian threading with ISO threading (as did Hillrider in his post above). For track cog or freewheel threading, the ISO standard is not just compatible with British threading: ISO adopted British threading dimensions for their rear hub threading standard. "Compatible" in this case means identical. There is no difference between ISO freewheel/track cog threading and and British freewheel/track cog threading.
    That's basically correct. There is theoretically a 5/1,000" difference in diameter, too small to matter in practice.

    This bit of misinformation came from Surly...The early versions of Surly's track sprockets had insufficient thread depth, and they wrecked some hubs. Surly initially came up with this theory about a threading difference to explain the problem.

    Ultimately, Surly revised the design of their sprockets to provide adequate threading, and the problem disappeared.

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  7. #7
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    Quote Originally Posted by Trakhak
    ISO (International Standards Organization) is not Italian threading. For track cogs and freewheels, there is no difference between ISO and British threading. From Sheldon's site:

    Most ISO standards are compatible with British standards.
    Good catch and sorry about the misinformation. I was thinking of the dimensions of square taper bottom brackets where ISO is the same as Campy (i.e. Italian) and the alternate standard is JIS.

  8. #8
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    so is 1.37x24tpi compatible with 1.375x24 tpi?
    or is that 2 different things?

  9. #9
    Old fart JohnDThompson's Avatar
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    I suspect the OP may mean lockring threading rather than cog threading. Campy and Miche use 1.32" x 24 TPI left hand thread; ISO lockrings are 1.29" x 24TPI left hand thread.

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