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  1. #1
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    650b with 47mm compatibility

    I went on a gravel ride the other day and looked over at people that were demo'ing the Open Ups and wished I was them. While I like the Open Up frameset, it's a bit on the pricier side and I'm hoping I can still get away with one bike that functions as both a CX and gravel bike. So this kinda begs the question, how do I know if a bike will fit 650b rims with 45-47mm tires? Many CX frames come with 40mm tire clearance on a 700c rim these days. This is also the max tire size of the Open Up. Does this mean the 650 setup will fit? I noticed the Open has a dropped stay on the right side. It seems like this isn't a requirement per se, but used by Open to keep the seat stays short.

    Anyone have experience with this and care to chime in with their setup?

  2. #2
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    The droopy chainstay isn't about tires as much as crankset and BB clearance....which becomes a real problem with 700x40mm tires combined with racy-short 420mm stays. 1X is less of a problem than roadie 2x which is

    Generally...the only way you "know" is if you have a review of someone riding that specific tire combination who posts photos. Generally "clearance" declared by a maker is the "you'd better never have a spoke break or a rock stuck to your tire" figure. The caveat with 650B conversions, is that you are lowering the ground clearance. E.g. the BB drop (WRT the axles) remains constant, however the BB height WRT the ground is reduced. Now Open says they created that frame with 650B in mind, which is good as it will handle the way they intended--whereas 700C might feel a bit like a turtle-on-stilts.


    OpenUP claims a 650Bx53mm tire will clear the back end

    These days "CX" and "Gravel" can mean two very different geometries-or the same geometry. The OpenUP is a fairly slack geometry with a lower BB than traditional aggressive CX angles and 65mm BB.
    "Refreshingly Unconcerned With The Vulgar Exigencies Of Veracity "

  3. #3
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    Quote Originally Posted by Marc View Post
    The caveat with 650B conversions, is that you are lowering the ground clearance. E.g. the BB drop (WRT the axles) remains constant, however the BB height WRT the ground is reduced.
    From my understanding 650b with a 45mm tire will have the same BB drop (WRT to ground) as a 700x35

  4. #4
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    I regretted the last time I posted a picture of one of my bikes on this site. I'm hoping it doesn't happen here.

    Here is my Norco Search XR (60.5cm frame for reference).


    In the first picture, it's shown with some 2.2" MTB tires I threw on for a particularly muddy charity ride I did recently. The ByWays have no tread on the center bead and can get squirmy in the mud, so I put these on at the last minute. This is about as wide as you can get on the back and still clear the chainstays without concerns of a rub. I'm not really sure why would want wider tires on a bike like this anyway.



    These two are the standard gravel/dirt road setup with Boyd 650b's and 47mm WTB ByWay's





    I've got about 100 miles on the bike so far. Most of it on the ByWays on paved trails, and about 30 miles of mostly mud and a little asphalt. I can't wait to get it out on gravel.

    For what it's worth, I was pretty pleasantly surprised with how well this bike rolls on these wheels/tires. It's a great ride. I had a little more pressure than I needed for the first rides (28f/30r). I went a little lower on the MTB tires (26f/28r). I need to experiment with it a little more before I settle on a pressure.
    I have some 700c wheels I'll eventually put on to compare, but that won't likely happen until the cold/dark/wet season ends (Spring).

    If anyone has any questions about the bike, or the wheels and tires, let me know.

    Edit: And I should point out that yes, that is a dropper seatpost. It's activated by the left shifter. It was part of the stock build. I will be removing it for a standard (non-dropper) seatpost at some point before the summer riding season hits. Reasons?

    1. I have zero need for a dropper seatpost - I don't do the type of technical riding that warrants such a thing - and
    2. I need a seatpost with 20mm or so of setback in order to get the fit dialed in the way I want it. I'm not sure if there is such a thing as a dropper with 20mm of setback, but I won't be buying one (see Reason 1).

    Also, the cockpit is far from final. I do love the Easton carbon bars with that flare on them (came with the bike). I'm currently demo'ing a RedShift ShockStop 120mm -6 degree stem (mixed feelings about it so far), and I am considering replacing the SRAM 1x setup with an XT Di2 setup, so I haven't re-wrapped the bars (the orange is just a temporary overwrap).

    And lastly, the Portland Origami fenders were loaned to me for the muddy charity ride. They did a nice job of keeping the tires from slinging mud all over me, but they have been removed and returned to their rightful owner. Not something I'd use for gravel riding.
    Last edited by Migen21; 01-27-2018 at 12:55 AM.

  5. #5
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    WTB shows the frames their 650b x 47 tires will fit:

    https://www.wtb.com/pages/road-plus
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



  6. #6
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    Quote Originally Posted by alxrmrs View Post
    From my understanding 650b with a 45mm tire will have the same BB drop (WRT to ground) as a 700x35
    According to this article, a 650b x 47 is roughly the same diameter as a 700c x 30:

    WTB Byway 650B X 47 Tires: Getting Rolling -
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



  7. #7
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    Quote Originally Posted by Lombard View Post
    WTB shows the frames their 650b x 47 tires will fit:

    https://www.wtb.com/pages/road-plus
    This list is obviously incomplete. The Norco Search XR in the post just before yours easily fits 47mm tires (probably up to 52) and isn't listed.

  8. #8
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    Quote Originally Posted by Finx View Post
    This list is obviously incomplete. The Norco Search XR in the post just before yours easily fits 47mm tires (probably up to 52) and isn't listed.
    Interesting. Apparently WTB missed that one.
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



  9. #9
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    Quote Originally Posted by Lombard View Post
    WTB shows the frames their 650b x 47 tires will fit:

    https://www.wtb.com/pages/road-plus
    Thanks for the link. I'm guessing this isn't a comprehensive list though.

  10. #10
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    Quote Originally Posted by alxrmrs View Post
    Thanks for the link. I'm guessing this isn't a comprehensive list though.
    They apparently missed some. It's nice to see my gravel bike is on there. I definitely want to try this setup.
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



  11. #11
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    Quote Originally Posted by Finx View Post
    This list is obviously incomplete. The Norco Search XR in the post just before yours easily fits 47mm tires (probably up to 52) and isn't listed.
    Yup, in fact, the two lower pictures in that post have 47mm WTB ByWays installed. The top pictures has 2.2" MTB tires I installed for a particularly muddy charity ride. The 2.2" fit without rubbing, but it was pretty tight. Not something I'd suggest unless you are confident your wheels aren't going to flex much.

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