Converting my old MCR to 29 plus!- Mtbr.com
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  1. #1
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    Converting my old MCR to 29 plus!

    Ever since 29+ bikes appeared, i wanted to try this setup, but replacing my beloved MCR that i had since 2007 is not an option. Neither getting smaller wheels. So I let the idea go, until recently when rims & tires started to appear in all kinds of shapes and sizes. Perhaps i could fit a 2.8 tire upfront and 2.6 rear?

    I started by getting a Panaracer fat b nimble, the most undersized 3.0 tire out there, just to get an idea of what would fit. The fork is wide with plenty of clearance, but in the rear the tire would barely rotate, as expected. I've calculated that I could fit slightly undersized 2.6 tire, and Maxxis rekon seems to be the tire I was looking for.

    As for rims, after careful considerations i've decided to go for Stans Centry rims, 32mm ID. It had identical depth as my original 20mm ID rims, making it possible to just swap the rims without rebuilding the wheels or getting new spokes.

    And here is the result:
    Converting my old MCR to 29 plus!-mcrplus1.jpg
    '
    Converting my old MCR to 29 plus!-mcrplus2.jpg

    Upgrading from 2.1 tires on 20mm ID rims to this makes a huge difference! I love the looks and how it rides, it feels like I have found a great balance between gaining the benefits of big tires and keeping most of the agility of traditional xc tires.

    The front tire measure 2,69 and rear tire 2,56 (after stretching). The chainstay clearance is 2,5mm and seatstay clearance is 3mm. The margins are minimal but I haven't noticed any rubbing yet.
    Converting my old MCR to 29 plus!-marginal1.jpg
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    Converting my old MCR to 29 plus!-marginal2.jpg

  2. #2
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    Nice to know. I have an older SIR and have used Kenda Slant Six 2.35, but am wondering how big I can go. Those tires where mounted on old Crest rims with 21 internal width, so going up to a 30i and maybe a 2.5 is in the future.

  3. #3
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    Quote Originally Posted by offrhodes42 View Post
    Nice to know. I have an older SIR...
    That was my intention with this thread, to show what actually fits, in case someone else has similar upgrade ideas. Older SIR & MCR has the same tire clearance. A true 2.5" tire on 30mm ID rim will fit with good margins.

    Maxxis Rekon 2.6" will also fit since it is a bit undersized. If it was a true 2.6" tire i would probably had to slightly trim the edges on the side knobs to prevent the tire from rubbing against the frame.
    Last edited by Transwave; 08-18-2018 at 08:01 AM.

  4. #4
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    Thanks for compiling this info. I just picked up a used MCR and I'm interested in putting the widest tire possible on it (27.5+/29).

    Do you think a a 27.5x3.0 tire would fit like this combo: https://www.amazon.com/Bridger-Brake...56H8W6C5WA5GEX

    I've seen reports of users installing a 27.5x2.8 on the MCR, but no confirmations of the 3.0.

    EDIT: Additionally, I have a Sun Ringle Charger Comp wheelset with a 28mm internal width. Do you think I could still run a 29x2.6" tire in the back?

  5. #5
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    Quote Originally Posted by JcConnell View Post
    Do you think a a 27.5x3.0 tire would fit like this combo: https://www.amazon.com/Bridger-Brake...56H8W6C5WA5GEX

    I've seen reports of users installing a 27.5x2.8 on the MCR, but no confirmations of the 3.0.
    I am afraid that a 3.0 tire, regardless of wheel size, won't fit in the rear, since it will be almost as wide as the widest point on both seatstays and chainstays. It will probably rotate but without any margins at all.

    Quote Originally Posted by JcConnell View Post
    Additionally, I have a Sun Ringle Charger Comp wheelset with a 28mm internal width. Do you think I could still run a 29x2.6" tire in the back?
    If you are using a slightly undersized 29x2.6" tire, like Maxxis Rekon, it will fit just fine. Mine did so i can recommend getting those. Other 2.6" tires should also fit if you are prepared to trim the edges of the side knobs by 1mm or so.

    I would definitely go for the 29x2.6 option.

  6. #6
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    Thanks! I was just concerned that my wheels might be too skinny. I've found out since the last post that the internal width of my rims are actually 23mm. The outer width is 28mm.

  7. #7
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    Quote Originally Posted by JcConnell View Post
    Thanks! I was just concerned that my wheels might be too skinny. I've found out since the last post that the internal width of my rims are actually 23mm. The outer width is 28mm.
    Ah, too bad, i28 wheels would have been perfect. IMHO 2.4" tire is the absolute maximum that would fit a i23 rim without becoming unstable, specially at lower tire pressures.

  8. #8
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    Any updates. I am thinking of putting Bontrager XR4 2.6 on Stans Flows (think they are 30mm inside)

    Sent from my SM-G892A using Tapatalk
    TREK EX9 27.5

    NINER MCR 9 (Moondust)

    GIANT REVOLT ADVANCED 1

  9. #9
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    Quote Originally Posted by sxr-racer View Post
    Any updates. I am thinking of putting Bontrager XR4 2.6 on Stans Flows (think they are 30mm inside)
    My second season with the 29+ setup is coming to an end and still love it! After some hard riding i realized that i needed a little more clearance for my rekon 2.6, especially in muddy conditions, so i trimmed the edges of the side knobs a little.

    Upfront i am considering getting a chupacabra, it is 100g heavier than fat b nimble but has a larger volume. That never hurts when riding full rigid
    Converting my old MCR to 29 plus!-img_20190715_191416.jpg
    '
    Converting my old MCR to 29 plus!-img_20190918_132754.jpg
    Last edited by Transwave; 09-27-2019 at 12:49 AM.

  10. #10
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    Just popped a Bontrager XR4 3.0 on my Flow Rims and took off my Reba and put the Niner fork back on.
    TREK EX9 27.5

    NINER MCR 9 (Moondust)

    GIANT REVOLT ADVANCED 1

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