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  1. #1
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    Design consideration for XX1?

    I have been thinking about building up a bike with SRAM's new XX1 drivetrain. The bike will probably be a custom ti deal. Does running XX1 open up the possibilities for really short chainstays? What are the other design characteristics?

    Thanks guys.

  2. #2
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    It lets you do things that having a front D would prevent.... mostly for full suspenshion designs.

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    Looking forward too...

    Quote Originally Posted by Fuglio View Post
    It lets you do things that having a front D would prevent.... mostly for full suspenshion designs.
    That's what I thought. I suppose it's too early for any of the builders to design a frame specifically for the drivetrain.

  4. #4
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    Quote Originally Posted by GlazedHam View Post
    That's what I thought. I suppose it's too early for any of the builders to design a frame specifically for the drivetrain.
    I guess you haven't been keeping up with Walt, huh?

  5. #5
    pvd
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    XX1 is silly.

  6. #6
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    Quote Originally Posted by Live Wire View Post
    I guess you haven't been keeping up with Walt, huh?
    Is it better then His 10 speed specific frame?

  7. #7
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    Here are the problems I've run into, taking it as a given that you want to use the group in the first place:
    -The chainline is narrower than what many people are used to (partially in order to allow the use of the 42t cog which sits inboard from the cassette body/driver) at 49mm, but the teeth are also wider than a conventional chainring so it's effectively a ~47mm chainline. This means less room for the chainring for situations where tire/chainstay/chainring clearance is tight.
    -The low Q (156) cranks are very narrow, especially if you are using long or outboard mounted (ie paragon low mount, paragon slider) dropouts. I have needed to use the 168 Q cranks for most of the frames I've done.
    -Many steel derailleur hangers are too thin and you'll need to use a washer/spacer to get the derailleur to shift to the 10t cog

    You can read all the specs here:
    http://cdn.sram.com/cdn/farfuture/Yp...ifications.pdf

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  8. #8
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    Quote Originally Posted by pvd View Post
    XX1 is silly.
    Grown men riding bicycles are silly.

    I mean most of us have taken a adolescent activity and turned it into a colossal waste of time and money.

    That said, I think XX1 is pretty awesome. I see 1x11 or 1x10 at some point in my personal future.

    Short chainstays are great and all but really 420mm to 430mm stays are plenty short. If you look back at what 26er race bikes had most of the top race bikes were in the same range. The chainstays give you wheel placement for weight balance and wheelbase length.

    I think 420mm stays would be fine with XX1 provided you took care to manage the chainline and the tire clearance.
    Mark Farnsworth, Raleigh, NC
    http://farnsworthbikes.com

  9. #9
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    tight

    I'm doing a 420 CS frame right now for XX1 and unfortunately the person wants to run a 32t instead of the 28t. That makes it even tighter and I'm not sure it's going to fit unless I dimple BOTH sides (see picture). It's drawn with a 2.35 Panaracer Rampage and the wider version of the XX1 cranks and the chainstay is one of the new Dedacciai's.

    I would say they are less useful for short-chainstay frames than I thought they'd be but depends on what you call 'short.'

    A 104BCD 3x crank only running a 30, 31 or 32 may still be the winner in what you can use on super short stay 29ers but the chainline sucks.Name:  chainstay-xx1.jpg
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  10. #10
    J_K
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    I'm running XX1 32t 156mm q-factor cranks on my 419mm CS 29er, I'm using the cranks with 10spd cassette and type 2 derailleur. 15mm clearance between the chainstay and the crank arm, I had to dimple the chainstay for the chainring clearance. But keep in mind this is with the chainstays too much outboard on the BB shell, thats because of the miss measuring the cut length.


  11. #11
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    Quote Originally Posted by J_K View Post
    I'm running XX1 32t 156mm q-factor cranks on my 419mm CS 29er, I'm using the cranks with 10spd cassette and type 2 derailleur. 15mm clearance between the chainstay and the crank arm, I had to dimple the chainstay for the chainring clearance. But keep in mind this is with the chainstays too much outboard on the BB shell, thats because of the miss measuring the cut length.

    Nice! Can you show a closeup on the chainring/tire/chainstay clearance area where you dimpled? I am curious how it looks there since I'm going to be doing the same thing soon. How does it shift with the 10 in back and with what chain? Sorry for hijack...

  12. #12
    J_K
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    Quote Originally Posted by Meriwether View Post
    Nice! Can you show a closeup on the chainring/tire/chainstay clearance area where you dimpled? I am curious how it looks there since I'm going to be doing the same thing soon. How does it shift with the 10 in back and with what chain? Sorry for hijack...
    No closeups, but still something. Tire is 59.5mm wide and diameter is 747mm, there's 7mm clearance to the chainstays. I would have needed to dimple the chainstays for the tire clearance if the chainstays had been done correctly, but done this way I only had to dimple for the chainring clearance.
    Shifting is perfert with shimano 10spd chain, I have no reasons to go to full XX1 drivetrain.

    I'll try to take better pics of the clearance if needed. 32t chainring is bigggest I would fit this frame, too much dimpling needed for bigger ring.


  13. #13
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    Quote Originally Posted by pvd View Post
    XX1 is silly.
    Could you elaborate a bit on why, Pete?

    Truls

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    Quote Originally Posted by Walt View Post
    ....but the teeth are also wider than a conventional chainring so it's effectively a ~47mm chainline.
    -Walt
    great info Walt.... good to hear from another full-time framebuilder here!

    I'm building a frame right now for 27.5"/650B, 2.25 Nobby Nics, 54mm wide at the knobs. There is loads of room for this combination, with an estimated 3mm of clearance from a 32 tooth chainring to the chainstay. With Columbus Zona S-bend chainstays, I estimate about 4mm clearance between the crankarms and the chainstays with the narrower Q156 cranks.

    Having ridden a series of bikes with all the gears available sequentially (Rohloff hub bikes) I can't wait to try XX1. Being able to wind up and down through the gears using only one hand puts a big grin on your face after using front derailleurs for 31 years....!

  15. #15
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    I'm getting ready to build a 29er with XX1 and was considering using an 83mm BB shell to help with chainring and tire clearance issues. Anybody have any comments as to positive or negative?

  16. #16
    DWF
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    At the risk of repeating myself, for you guys that are having a hard time coming up with an economical/simple means of wrapping a 29er tire with short stays, look at using unicrown fork blades as chainstays. I've done it many times in the past, it works, it's fairly light (especially relative to a lot of these plate style yokes I've been seeing). Yes, you will probably have to crimp them, but that's about the easiest thing about building any short stay bike.
    A man must have enemies and places he is not welcome. In the end we are not only defined by our friends but those against us.

  17. #17
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    Well, there is no XX1 crank for an 83mm shell, but you could run a non-XX1 crank + the rest of the XX1 drivetrain and offset to the driveside to fix the chainline, I guess.

    If you use the MRP bling rings, you get a few extra mm for the chainring.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
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  18. #18
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    Quote Originally Posted by DWF View Post
    At the risk of repeating myself, for you guys that are having a hard time coming up with an economical/simple means of wrapping a 29er tire with short stays, look at using unicrown fork blades as chainstays. I've done it many times in the past, it works, it's fairly light (especially relative to a lot of these plate style yokes I've been seeing). Yes, you will probably have to crimp them, but that's about the easiest thing about building any short stay bike.
    I totally agree. Chainstays/Fork blades as Tapered items are surprisingly similar in wall thickness and dameters and can be inter-changed. I have done this and will continue to do so where and when the need arises. The key with using the unicrown is in the oval section immediately after the bend, it is nice and narrow, plus, I have found fork blades to be more amenable to a bit of bending further along its length than round 4130.

    Eric
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