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Thread: Round MTB Stays

  1. #1
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    Round MTB Stays

    I'm thinking about 7/8" round 4130 MTB chainstays. Are any of you using similar stays? Would you use .035" for most applications?

    I'm considering getting batch made by the bender who makes my LD stems. UI tried to bend some myself and was unable to keep it from crimping. Would any of you be interested in ordering a some with me? I'm estimating $40/pair. You'd be responsible for flattening/forming the stays for desired tire and chainring clearance. The crank pictured is a XT FC-M785.

    Round MTB Stays-mtb.jpg
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    Hey Joel, why don't you give me a day or so to monkey around in my shop a little bit before you pull the trigger on that order.
    I've bent my own handlebars out of 7/8"x .049 with good success.
    I also picked something up the other day that might make a sweet crimping punch for this application.

    jake

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    Quote Originally Posted by j-ro View Post
    Hey Joel, why don't you give me a day or so to monkey around in my shop a little bit before you pull the trigger on that order.
    I've bent my own handlebars out of 7/8"x .049 with good success.
    I also picked something up the other day that might make a sweet crimping punch for this application.

    jake

    Thanks, Jake. Let's see if folks prefer .035" or .049" and then we can start experimenting.
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    Sounds good, you have my curiosity up now though, I'm going to finish my sandwich and hit the shop.
    i'll keep you posted.

  5. #5
    pvd
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    0.035" is more than enough, especially for 7/8". At FCC we did 3/4" 0.035" chainstays.

    The thing is, why? At those old companies, there wasn't much to choose from which drove the decision, but now there are much better alternatives. I would't use round if my life depended on it.

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    What centerline radius and stay bend angle are you shooting for?

  7. #7
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    Quote Originally Posted by pvd View Post
    0.035" is more than enough, especially for 7/8". At FCC we did 3/4" 0.035" chainstays.

    The thing is, why? At those old companies, there wasn't much to choose from which drove the decision, but now there are much better alternatives. I would't use round if my life depended on it.
    It'll interface nicely with a 12mm through-axle dropout I'm making, lateral stiffness, and it looks super cool. Here's Frank The Welder's:



    Quote Originally Posted by stuntnuts View Post
    What centerline radius and stay bend angle are you shooting for?
    I'm at 8* right now and it'll be 3" clr if my bender makes it. I'm not sure what die Jake has.

    -Joel
    Last edited by Clockwork Bikes; 12-26-2011 at 06:03 PM.
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    So heres a quickie S-bend I just made.

    looks like my bending rig will bend it without ripples but it leaves a little dip where the the dies starts out. That may go away if I use the other bending arm.

    Once you crimp it for clearance the dip pretty much goes away so If you just wanted single bend it would be no problem.
    Crimping it with a 2.5# weight plate also adds to the radius as you bend it.

    This is a deda zero tre on top of what I just bent for comparison;

    Untitled by Huckleberry cycles, on Flickr


    Untitled by Huckleberry cycles, on Flickr


    Untitled by Huckleberry cycles, on Flickr

    this is a 700x35c tire;

    Untitled by Huckleberry cycles, on Flickr

    heres the dip, I don't think it would show up but you can feel it with your finger, again, it might go away with the other arm;

    Untitled by Huckleberry cycles, on Flickr

    Oh, one more thing, This was done with .049, seems really heavy and would indeed be very stiff. I didn't have any .035.

    BTW, are you tig welding now Joel?
    Last edited by j-ro; 12-26-2011 at 05:34 PM.

  9. #9
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    .750 will do a 3" CLR up to about 45 degrees in a rotary draw bender if you know the technique. I'd imagine .875 should do 8-10 degrees around a 3" CLR easy without a mark, at .035 thickness. .045 is way beyond necessary, just adding extra weight with no real benefit (IMO).

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    Joel,

    Yes, you can bend your own stays in house...as mentioned many times before on the forums, the trick is to fully encapsulate the tubing to prevent any deformity during the process.

    I've got four different bending options in house...an enerpac press, a JD2 bender, an Anvil Mr. Bendy, and a Diacro. Each serves a different shaping need.

    Attached is a photo of two stays; black on left is a .750x.035 4130, silver or right is a .875x.035 4130, both bent at 12 degrees with no dimpling or deformity.

    The stay on the left was made on the Enerpac press, the one on the right was made with an Anvil Mr. Bendy.

    You can see that the shape of the bends are quite different, the left is a bit more acute and the right is a constant radius...the final look of the part drives which bender I use for the task.

    As you already know, it's worth investing in the right equipment.

    cheers,

    rody
    Attached Thumbnails Attached Thumbnails Round MTB Stays-bend-radius.jpg  

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  11. #11
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    I use .750 x .035 4130 for the SS/CS and make the bends with a JD2 with pretty good
    Results about every 5th one or so I get dimple that's noticeable.
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  12. #12
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    I'm with everyone else. 0.035 is fine. I use that for CS almost exclusively for trials bikes. Sometimes I go to 0.49 for some extra 'dent' protection but haven't really seem any difference so I would think for XC...non issue.

    I have to bend to get tire clearance as the tires are 63-64MM widths and the CS are completely slammed. Bending .049 no issues up to 40 degrees and I can sometimes go that much with .035 without any real noticeable deformation. Protools bender 3 CLR.

  13. #13
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    If you haven't made a 29er with fully round 22.2mm chainstays, you don't know what you're missing. You think regular chainstays have okay torsional stiffness out of the saddle, and then you make a frame with 22.2 constant diameter stays..............night and day. Well worth doing Joel.
    No longer member of the bike industry nor society, so don't hassle me.

  14. #14
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    In the 1990s Marin made steel frames with 0.75" OD seatstays and chainstays. They were straight gauge 0.035" wall thickness 4130 tubing. They called them Afterburner stays. They used very beautiful rear dropouts.
    Attached Thumbnails Attached Thumbnails Round MTB Stays-marin_rear_dropout_575.jpg  


  15. #15
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    Quote Originally Posted by forwardcomponents View Post
    In the 1990s Marin made steel frames with 0.75" OD seatstays and chainstays. They were straight gauge 0.035" wall thickness 4130 tubing. They called them Afterburner stays. They used very beautiful rear dropouts.
    I have a couple of those dropouts, in case anyone ever needs one for a repair or something.

  16. #16
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    Quote Originally Posted by j-ro View Post
    So heres a quickie S-bend I just made.

    looks like my bending rig will bend it without ripples but it leaves a little dip where the the dies starts out. That may go away if I use the other bending arm.

    Once you crimp it for clearance the dip pretty much goes away so If you just wanted single bend it would be no problem.
    Crimping it with a 2.5# weight plate also adds to the radius as you bend it.

    This is a deda zero tre on top of what I just bent for comparison;

    Untitled by Huckleberry cycles, on Flickr


    Untitled by Huckleberry cycles, on Flickr


    Untitled by Huckleberry cycles, on Flickr

    this is a 700x35c tire;

    Untitled by Huckleberry cycles, on Flickr

    heres the dip, I don't think it would show up but you can feel it with your finger, again, it might go away with the other arm;

    Untitled by Huckleberry cycles, on Flickr

    Oh, one more thing, This was done with .049, seems really heavy and would indeed be very stiff. I didn't have any .035.

    BTW, are you tig welding now Joel?
    In the pic with the 2.5lb plate is the reciever block of wood radiused channel or does it just have a
    straight channel cut thru it?
    Last edited by todwil; 01-11-2012 at 02:09 PM.
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  17. #17
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    7/8" chainstays yes, but now with the overwhelming superiority of disc brakes, even 3/4" seat stays don't make much sense on a hardtail MTB that's not more FR or jump oriented. 5/8" seat stays ride better. IMHO, ymmv.
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    Quote Originally Posted by todwil View Post
    In the pic with the 2.5lb plate is the reciever block of wood radiused channel or does it just have a
    straight channel cut thru it?
    Its just an open tube block in 7/8. If I were to do more of them I would make it deeper to contain the sides better.

    If you meant was the channel concave to help form the radius the answers is no but that would work well I would think.

  19. #19
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    Quote Originally Posted by j-ro View Post
    Its just an open tube block in 7/8. If I were to do more of them I would make it deeper to contain the sides better.

    If you meant was the channel concave to help form the radius the answers is no but that would work well I would think.
    So just straight across but maybe a litle deeper like 3/4 of the width to support more of the tubing I have the 2.5 lb weight so I need to make wood block. Did you use a hole saw
    Or a rotter?
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    Quote Originally Posted by todwil View Post
    So just straight across but maybe a litle deeper like 3/4 of the width to support more of the tubing I have the 2.5 lb weight so I need to make wood block. Did you use a hole saw
    Or a rotter?
    Forstner bit, the deeper the better I would think.

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    3/4 VS 7/8 chainstays

    Honnestly, for those who have used both 7/8 and 3/4 x0.35 round chainstays, have you seen a huge difference or not.

    On paper, 7/8 is definitely stiffer but in the real world how does it show?

    I'm just asking because I'd like to avoid or minimise any dimpling for tire clearance.
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  22. #22
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    If you're going to crimp the crap out of them, make them thick.

    People seem to forget how crimped stays fail over time.
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    Playing the Devil's advocate again...

    How is a mega-crimped round chainstay any different than one that started out oval?

    IMHO traditional hardtail rear ends are super stiff and worrying a lot about lateral flex (or trying to create vertical flex) is a waste of time. Pick stays that won't break, will fit the tires you want, and will keep you from whacking your heels on them, and you're basically good.

    -Walt
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  24. #24
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    To add to the discussion, a practical thought.

    In repairing and aligning rear triangles, cold setting them in other words, round are hard to pull out. Oval are hard to pull as well, but indented ones bend easy.......what does that tell you?

    I'm with Walt on this one, I know it is topical at present to make your own, and why not, but there are limits and off the shelf is easy, but time proven.

    My 2 cents worth.

    Eric
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  25. #25
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    Quote Originally Posted by D.F.L. View Post
    If you're going to crimp the crap out of them, make them thick.

    People seem to forget how crimped stays fail over time.
    I totally agree - I see some extreme crimping going on by some builders that I'm sure is going to fail within a few years.
    - Steve Garro, Coconino Cycles.
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