Results 1 to 27 of 27
  1. #1
    mtbr member
    Reputation:
    Join Date
    Sep 2010
    Posts
    774

    stainless steel 39 tooth rear cogs - interested ?

    I have come across a machinist who sells 4 bolt 20 tooth chainrings (64mm bcd) on ebay. He would be willing to produce 5-10 cogs at a cost of $30-40 each. I don't know how many people on this forum would be interested in ultra low gearing but it's worth a shot. I can't afford 300-400 dollars for the project and thought it would be easier to garner some interest from other riders. I am sure folks here are aware of the offerings from Action-Tec. I have an Action-Tec 39 tooth cog made of titanium. It works great and is fairly durable, but the 89 dollar cost is prohibitive. If anyone wants to contact this person directly here is a link to his chainrings for sale.

    eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices

    It would be great if enough people are interested so that we can make this happen.

  2. #2
    mtbr member
    Reputation: mikeridesabike's Avatar
    Join Date
    Feb 2009
    Posts
    1,866
    Wow - a 20 x 39 - now that would be what I call a granny gear!
    Friends don let friends ride road bikes.
    http://www.facebook.com/mikebmiller

  3. #3
    www.derbyrims.com
    Reputation: derby's Avatar
    Join Date
    Jan 2004
    Posts
    6,764
    Do Sram and Shimano derailleurs shift into a 39 cog OK? Has it been done it yet?

  4. #4
    mtbr member
    Reputation:
    Join Date
    Sep 2010
    Posts
    774
    I use both Sram and Shimano derailleurs on 38/39/40 tooth cogs. I use a number of different gear ratios on my various bikes

    26"- 20/39 & 20/38
    27.5" - 18/40
    29" - 18/40

    I've been riding the 39 tooth Action-Tec cog on my 26" mavic/xtr wheel for a couple of years now with no issues.

  5. #5
    mtbr member
    Reputation:
    Join Date
    Oct 2006
    Posts
    167
    my goal is to conquer this hillclimb and im goin need really low gearing.. my Trance has a 22 front
    can a 39T cog be installed on my 9speed cassette instead of the 34?

    BCI at Fargo Street 3/16/03

  6. #6
    Recovering couch patato
    Reputation: Cloxxki's Avatar
    Join Date
    Jan 2004
    Posts
    14,017
    Custom derailer hanger is all you need.

  7. #7
    Bite Me.
    Reputation: cutthroat's Avatar
    Join Date
    Mar 2004
    Posts
    4,531
    Quote Originally Posted by frank6262 View Post
    my goal is to conquer this hillclimb and im goin need really low gearing.. my Trance has a 22 front
    can a 39T cog be installed on my 9speed cassette instead of the 34?

    BCI at Fargo Street 3/16/03
    Pull off one of small loose cogs (the #2 cog is usually the better option so you keep the smallest one with the attached spacer and knurled surface for the lock ring), put the new cog behind the 34 with a spacer if necessary and re-mount the cassette. My worry would be if the freehub body could take the torque - since the new cog isn't pinned or on a spider it will dig into the freehub if it's not steel.
    When I see an adult on a bicycle, I do not despair for the future of the human race. ~H.G. Wells

  8. #8
    mtbr member
    Reputation:
    Join Date
    Sep 2010
    Posts
    774
    I've been using my 38/39/40 tooth cogs on Shimano/Sram hub bodies for a couple years with no issues.

  9. #9
    Bite Me.
    Reputation: cutthroat's Avatar
    Join Date
    Mar 2004
    Posts
    4,531
    Quote Originally Posted by phoenixbikes View Post
    I've been using my 38/39/40 tooth cogs on Shimano/Sram hub bodies for a couple years with no issues.
    Good to hear - some hubs are better than others. Most of the Shimano stuff is steel, but the lighter high-end stuff is aluminum and can cause problems. King and WTB/American Classic had some issues. I think American Classic now incorporates a steel spline on their aluminum free hubs to prevent gouging. If the cog gouges far enough it can make it impossible to remove. Just figured I'd give the OP a heads up on that.
    Attached Thumbnails Attached Thumbnails stainless steel 39 tooth rear cogs - interested ?-wtb_freehub_body_.jpg  

    When I see an adult on a bicycle, I do not despair for the future of the human race. ~H.G. Wells

  10. #10
    mtbr member
    Reputation:
    Join Date
    Oct 2006
    Posts
    167
    ok count me in for one 39T steel cog...
    also where do get the custom derailer hanger for my Giant Trance !?

    frank

  11. #11
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    273
    In the 70's custom builder Ron Boi imported 130 mm axles from Campagnolo. He used these to build dishless wheels with Suntour 6 cog freewheels. He found out there was room for another cog as long as it was 34 teeth so he welded them directly to the next cog on the freewheel. With a 39 tooth cog there is actually room for 2 additional cogs. You can find my setup by doing a google search. I removed the 1mm spacer behind the cassette filed the splines deeper so the cog fits 2mm closer to the spokes and used a dished cog so my setup is 4mm closer to the spokes than stock. What the cog makers need to do is build dished cogs like Ritchey did on 2 by 9 setup or build 2 cog pairs.

  12. #12
    NedwannaB
    Reputation: JMac47's Avatar
    Join Date
    Apr 2004
    Posts
    11,538
    Hate to come late to the party, but wtf would you be riding up to need a 39t rr cog? Thought it was a typo originally but realized not the case. Just curious.
    Wait whuuut, who did he tell you that!?!?....

  13. #13
    Uncle
    Reputation: Entrenador's Avatar
    Join Date
    Oct 2004
    Posts
    4,115
    1x9 set up, 39x11 rear, 34t up front? Sounds good to me.

  14. #14
    NedwannaB
    Reputation: JMac47's Avatar
    Join Date
    Apr 2004
    Posts
    11,538
    E tu Brute~?......
    Wait whuuut, who did he tell you that!?!?....

  15. #15
    dirtbag
    Reputation: ranier's Avatar
    Join Date
    Sep 2003
    Posts
    1,443
    Quote Originally Posted by Entrenador View Post
    1x9 set up, 39x11 rear, 34t up front? Sounds good to me.
    uhh... read post title again.

    39t rear cog, NOT a 39t chainring.
    Amolan

  16. #16
    NedwannaB
    Reputation: JMac47's Avatar
    Join Date
    Apr 2004
    Posts
    11,538

    Maybe YOU should

    Quote Originally Posted by ranier View Post
    uhh... read post title again.

    39t rear cog, NOT a 39t chainring.
    "Entrenador

    1x9 set up, 39x11 rear, 34t up front? Sounds good to me."


    Looks like that's exactly what he said to me!
    Wait whuuut, who did he tell you that!?!?....

  17. #17
    mtbr member
    Reputation:
    Join Date
    May 2005
    Posts
    2,190
    These huge rear cogs certainly open up some interesting possibilities provided you have the proper steel or TI freehub body. Do we really need 18-30 speeds when 9 or 10 might work with a 11-39 cog spread? I don't race so perhaps you do in that case? Maybe manufacturers should have a look at this possibility. My wish...Sram would develop a 2nd generation lightweight Hammerschmidt with an assortment of gearing choices. One may end up on my new Dakar B2 anyway.
    2016 Trek Remedy 8 29er
    2013 Banshee Spitfire V2 650b SOLD

  18. #18
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    273
    There are 3 reasons I built the 39 tooth rear cog. The first is chain grab. This is when a worn chain refuses to release from the chainring jamming the gears and damaging the chainstays. The larger the front gear is the harder it is to do this. The second is cogs and chains wear as the cube of the size so going from say a 20 front to 24 front and increasing the rear proportionally will increase the life of the chain by a factor of 1.7 With the larger gears you can choose to use more aluminum gears I will change to an aluminum 39 when I can make one. The third is ergonomics on the 39 rear I shift to the lower front at 7 kph and to the higher rear at 9 kph this is a difference of 1.29. so the ideal spacing is a 30 39 this is what I have. in the higher gears I go from 30 kph to 35 kph while using the 13 tooth back this is a difference of 1.16 so the ideal spacing is 13 15 this is also what I have. With optimal gearing I lose a cog this allows me to build dishless wheels.

  19. #19
    Uncle
    Reputation: Entrenador's Avatar
    Join Date
    Oct 2004
    Posts
    4,115
    Quote Originally Posted by zerodish View Post
    With optimal gearing I lose a cog this allows me to build dishless wheels.
    zerodish, good stuff. Always interesting to read about the refinement and problem solving processes when customizing stock parts. Wondering off topic a bit, but there's a long thread somewhere on here about using SS specific hubs to get similar results. With nothing but stock parts, I managed to get just 5 cogs onto my SS hub, but others had luck with as many as 8 IIRC. Any experience with the SS specific hubs, and if so, how did it go?

    -E

    ps- Chain Grab, or chain suck:
    I've had some success delaying the occurrence of CS by using 24t steel granny rings that are often dirt cheap on Ebay. The tiny alloy 22t rings are terribly prone to wear and are useless when the suck starts. I also prefer the 24t because the drop down isn't as drastic, so I can keep the bike moving immediately after a downshift.
    Last edited by Entrenador; 04-05-2012 at 11:33 AM.

  20. #20
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    273
    hxxp://share.ovi.com/album/currentresident.bicycle it's all right here download it the site will be discontinued may 30 and I will try to move everything to flicker. I sand down Shimano cassettes to 29mm and use 8 gears with 9 gear spacing. Shimano 7 cog cassettes are not very strong so I'm carefull to keep down the torque.

  21. #21
    mtbr member
    Reputation:
    Join Date
    May 2011
    Posts
    2
    I just bought 39T cog Action Tec, I have Shimano XT M772 9-spd rear derailleur, I don't have problem shifting up to 39T, but it won't shift down from 39T. What is the model of your Shimano?

  22. #22
    mtbr member
    Reputation:
    Join Date
    May 2011
    Posts
    2
    Quote Originally Posted by phoenixbikes View Post
    I use both Sram and Shimano derailleurs on 38/39/40 tooth cogs. I use a number of different gear ratios on my various bikes

    26"- 20/39 & 20/38
    27.5" - 18/40
    29" - 18/40

    I've been riding the 39 tooth Action-Tec cog on my 26" mavic/xtr wheel for a couple of years now with no issues.
    I just bought 39T cog Action Tec, I have Shimano XT M772 9-spd rear derailleur, I don't have problem shifting up to 39T, but it won't shift down from 39T. What is the model of your Shimano?

  23. #23
    mtbr member
    Reputation:
    Join Date
    Aug 2010
    Posts
    1,797
    Quote Originally Posted by mikeridesabike View Post
    Wow - a 20 x 39 - now that would be what I call a granny gear!
    I like a nice low granny gear, but at that point you may as well walk.

    The 39t cog would be nice for a 1x9 or 1x10 setup, though.

  24. #24
    mtbr member
    Reputation: Morpheous's Avatar
    Join Date
    Mar 2006
    Posts
    497
    1X is the current movement for TR/EN//AM/OM. Allows chain retention guide use in the front and Short cage rear Der. for the DH side of the ride. 38T should be plenty in the back. Run a 32F - 11-38 rear cogset. Why 39T is the question, is that a limitation of cog design for this tooth count range?
    Last edited by Morpheous; 05-11-2012 at 11:49 AM.

  25. #25
    mtbr member
    Reputation:
    Join Date
    Sep 2010
    Posts
    774
    Quote Originally Posted by jabrabu View Post
    at that point you may as well walk.


    Some people live at high elevation......

    I live at 7,000 ft and the mountains here go up to 12,000 feet. Further north, they go up to 14,000 feet. Not sure if riding for hours at extremely high elevation is something you do much, but in the rockies it's nice to have a bailout gear when you hit a wall at 10,000 feet and you're not exactly fresh anyway.

    And some of us prefer to actually RIDE our bikes.

    If I might as well walk, I might as well sell my mtn bikes and start hiking........

  26. #26
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    273
    The tourney TX works on the 39 I estimate it's limit at 40 teeth. It has a bit of play and does not work well with index shifters.

  27. #27
    mtbr member
    Reputation:
    Join Date
    Sep 2005
    Posts
    1,142
    Need to make aluminum spiders that hold chainrings and gives a wide surface interface with the cassette driver. A spider that holds a 39, 34, and 30,tooth gears,ect ect all the gear sizes that you need have already been made, unfortunately the bolt patterns are all over the place. It might be possible to make a spider that holds gears of all different bolt patterns, but the best would be to have gears that share common hole patterns so chainring bolts could be used to hold it together, custom gears would need to be made.Hardcoating them would be a nice finnishing touch, starting to sound really incredibly expensive. Fantasy cog stack might be 39,35,31 on one spider 28,25,22 on the next, then 19,17,15 ,13 as interlocking singles 1x10 with a 35 up front would work for me.

Similar Threads

  1. stainless steel 39 tooth rear cogs - interested ?
    By phoenixbikes in forum 29er Bikes
    Replies: 2
    Last Post: 01-11-2012, 08:55 PM

Members who have read this thread: 0

Posting Permissions

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

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2019 VerticalScope Inc. All rights reserved.