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  1. #1
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    WTB Sprocket problem?

    Bit of a weird problem with my new WTB 20t sprocket.

    I got it to replace my narrow base cheap-o cog on my new Hope SS hub. I fitted it last night and decided to oil the chain while I was at it. As I back pedaled the bike the chain was catching on the tops of some of the teeth and making a "clunk" noise.

    Compared to the old cog the WTB has quite square cut teeth with little taper at the tip. This might be exaserbated by running the 32:20 gear ratio (hey, its a 29er and its hilly around here!)

    Anyone else had this? Should I just machine a 45deg lead in on the top of each tooth?

    Pictures to follow...

    Thanks,

    Alex
    "Put any one on one of these singlespeed bikes and they could not help but have fun"
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    Otis Guy talking about klunkers c1976

  2. #2
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    Hmmm...I was just about to buy one of these. Be interested to find out more.

  3. #3
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    "As I back pedaled the bike the chain was catching on the tops of some of the teeth and making a "clunk" noise.
    "

    That sounds like the chain is worn. The distance between the pins increases and because of that the chain will ride higher. Something that can be more profound on large teeth.

    Whats the wear of the chain? Maybe an idea to replace that. Also replace the front ring because if the chain is this much worn the front chainring will also be shot.

  4. #4
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    The chain is not worn, still well in the blue on the Park Chain Checker. It did not do it with the old cogs, only the new one and I am pretty sure its down to tooth profile.

    Here is a photo of the old sprocket (top) and the new WTB sprocket (bottom / fitted)

    Link if the photo does not work:
    http://lh6.ggpht.com/_DwSSaopGCuw/Sc...comparison.jpg



    Oh, and a photo of the last ride to show that we do have sunshine and dry trails in the UK (sometimes!)



    Alex
    Last edited by Singlespeedpunk; 03-22-2009 at 06:00 AM.
    "Put any one on one of these singlespeed bikes and they could not help but have fun"
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    Otis Guy talking about klunkers c1976

  5. #5
    meatier showers
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    I don't have any personal experience with WTB's cogs, but they recently took quite a hammering here. Those that owned them were consistently disappointed.

    Sorry.

    --Sparty
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  6. #6
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    Wrong Chain...

    The WTB cogs are for 1/8th inch pitch chains not 3/32nd pitch chains. You need a fatter chain, a BMX chain.

    Cog description here.

    JOEY

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    Sparty, bummer...well it was 8 so no great loss and a lot less than Surly or King on this side of the pond!

    1/8" pitch you sure? The pitch of the chain is the same, its the width that varies...sorry, pet gripe of mine.

    I have seen people in the shop trying to run 3/32" chains on 1/8" cogs* and the chain does not sit down on the tooth bed. This chain (PC850) is sitting on the cog correctly and has some "wiggle room" on the width, just not leaving it smoothly.

    I know my engineering degree was a few years ago but I remember the first lecture was on "Gear Tooth Geometry in Direct and Chain Applications" I am pretty sure it was a test to see if we could stay awake but I am sure the WTB cog is too square on the top and does not allow for the cord curve of the chain...yawn

    I have one thing to try and I'll report back.

    Alex

    *9sp chains on early Surly Stainless rings are another problem I have seen, and again different to this.
    Last edited by Singlespeedpunk; 03-23-2009 at 02:28 AM.
    "Put any one on one of these singlespeed bikes and they could not help but have fun"
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    Otis Guy talking about klunkers c1976

  8. #8
    HHL
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    Chainline

    Maybe the new cog needs a perfect chainline, or a rat tail file application?

  9. #9
    one chain loop
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    we had problems with WTB cogs too as mentioned here.
    everything sucks but my vacuum cleaner.

  10. #10
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    I speak from experience...

    I have two WTB cogs that will work on nothing but 1/8th inch chains. I have seen the same thing you describe above, when folks come in my shop trying to use a 3/32nd chain on there fixies. 3/32nds chain just is not wide enough.

    JOEY

  11. #11
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    Quote Originally Posted by joeywv
    I have two WTB cogs that will work on nothing but 1/8th inch chains. I have seen the same thing you describe above, when folks come in my shop trying to use a 3/32nd chain on there fixies. 3/32nds chain just is not wide enough.

    JOEY
    Well I measured up the old pressed cog and the new WTB one, 2.30mm and 2.42mm wide respectivly. 3/32" = 2.38mm so they are not 1/8" cogs (3.17mm)

    Sounds like bad tooth profile...might drop WTB an email, too bad I binned the packaging. Ah well.

    SSP
    "Put any one on one of these singlespeed bikes and they could not help but have fun"
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    Otis Guy talking about klunkers c1976

  12. #12
    Misfit Psycles
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    Quote Originally Posted by Singlespeedpunk
    Well I measured up the old pressed cog and the new WTB one, 2.30mm and 2.42mm wide respectivly. 3/32" = 2.38mm so they are not 1/8" cogs (3.17mm)

    Sounds like bad tooth profile...might drop WTB an email, too bad I binned the packaging. Ah well.

    SSP
    despite your measurements (possibly your measurements demonstrate the inconsistency) WTB themselves say they are for 1/8" chains.
    RIGHT HERE
    when i used WTB wheels for builds i swapped out the cogs, it was easier then testing each one particularly since the rejection rate was >50% anyway...
    Expert of the Internet.
    BECAUSE I SAID SO

  13. #13
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    I know what they say but to be that far out on the width of the cog? Seems hard to swallow. Just to reitterate, it it not a problem with seating (tooth width) but tooth height and profile. I have a friend running one with a PC850 chain on his NS dirt bike with no issues and he is pretty hard on kit.

    Ill swap it out and see what WTB say. Guess I will save up for a Surly cog.

    SSP
    "Put any one on one of these singlespeed bikes and they could not help but have fun"
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    Otis Guy talking about klunkers c1976

  14. #14
    SSolo
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    Quote Originally Posted by Singlespeedpunk
    1/8" pitch you sure? The pitch of the chain is the same, its the width that varies...sorry, pet gripe of mine...
    Thanks for correcting the terminology...helps clarify and keep us all on the same page!

    Quote Originally Posted by Singlespeedpunk
    ...I know my enfineering degree was a few years ago but I remember the first lecture was on "Gear Tooth Geometry in Direct and Chain Applications" I am pretty sure it was a test to see if we could stay awake but I am sure the WTB cog is too square on the top and does not allow for the cord curve of the chain...
    I believe you are correct with this statement....iirc! Those are some way too square lookin teeth on the WTB cogs!!!!

    Quote Originally Posted by Singlespeedpunk
    ...*9sp chains on early Surly Stainless rings are another problem I have seen, and again different to this.
    Surly's site specifically says to use only 8-speed chains, NOT 9-speed chains with their cogs.
    Fat, drunk, and stupid is no way to go through life son...

  15. #15
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    Quote Originally Posted by Natedogz
    Surly's site specifically says to use only 8-speed chains, NOT 9-speed chains with their cogs.
    I was talking about the chainrings, not sprockets, sorry, I should have been clearer about it.

    I'll change the cog out today when I fettle the forks at work.

    Alex
    "Put any one on one of these singlespeed bikes and they could not help but have fun"
    -
    Otis Guy talking about klunkers c1976

  16. #16
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    same thing happened to me when swapped to a wtb cog. clicked for maybe a week or 4 rides then has been fine ever since. i am running an x9 chain with all surly cogs now...
    if you can stand the clicking run it for a few rides and the teath will get ever so slightly worn as well as the chain stretching.

  17. #17
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    something is not right with my WTB cogs

    Quote Originally Posted by Natedogz
    Thanks for correcting the terminology...helps clarify and keep us all on the same page!



    I believe you are correct with this statement....iirc! Those are some way too square lookin teeth on the WTB cogs!!!!

    I have 2 brand new WTB 20 T cogs and neither will work on 1/8" or 3/32",,,,,,,the squared off tooth profile is the problem IMO.........I have other WTB cogs and the teeth are not the same,,,,,hoping WTB will swap them out,will be contacting them this week

    Surly's site specifically says to use only 8-speed chains, NOT 9-speed chains with their cogs.
    see my reply above............

  18. #18
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    Quote Originally Posted by elrancho66
    see my reply above............
    Your reply above....where? No previous reply from you in this thread....
    Fat, drunk, and stupid is no way to go through life son...

  19. #19
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    sorry, my reply was inserted incorrectly

    Quote Originally Posted by Natedogz
    Your reply above....where? No previous reply from you in this thread....
    My reply ended up in between the quoted section,,,,,,,starts off " I have 2 WTB............."
    darn computer's!

  20. #20
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    Quote Originally Posted by elrancho66
    My reply ended up in between the quoted section,,,,,,,starts off " I have 2 WTB............."
    darn computer's!
    OK, now I understand....thanks for the clarification.
    Fat, drunk, and stupid is no way to go through life son...

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