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  1. #1
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    New question here. Fitting smaller tires on a plus-bike?

    Hello!

    Just bought my first trail bike, a used Rocky Mountain Pipeline 770 MSL, and it is so much fun!!! But, since my first bike is a plus bike I wanted to test out what more normal wheel size would feel like. So, I went online and ordered Maxxis Minion DHF 2.5 WT front and a Minion DHR 2.4 WT aft. Found these on sale, and people seem to like them.

    But, I just realized that it might drop bottom bracket height too much...

    I have read that outer diameter of plus sized wheels are about the size of normal 29'ers. So, would changing tires as I plan just mess up everything??

    I am an amateur, and pedal strikes happens all the time with my stock Rekon+ 2.8 tires.... But I am on a learning curve

    Since the tires I have ordered are still in the mail (online shopping) I can still return them free of charge. AND, since I work offshore, I am not at home and able to measure the diameter of my stock tires.

    So, is the outer diameter of the Minion DHF 2.5 WT and DHR 2.4 WT tires I ordered much smaller than the Rekon+ 2,8 tires fitted on a 27.5 rim (35 mm internal) ? Other aspects I am missing here??

    Help much appreciated

  2. #2
    mtbpete
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    Depending on the knob height the tires could be as much as .4 inches shorter. The biggest negative of a lower bb height is hitting more rocks and roots with the pedals. Give it a try. You may want to increase the shock preload to reduce the sag, but then you won't get as much travel.

  3. #3
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    You will be fine. Your bike has the bottom bracket about 25mm below the axles (bottom bracket drop).
    That's similar to numerous bikes that come with 2.5" or smaller tires.

  4. #4
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    Quote Originally Posted by ac1000 View Post
    You will be fine. Your bike has the bottom bracket about 25mm below the axles (bottom bracket drop).
    That's similar to numerous bikes that come with 2.5" or smaller tires.
    Not pertinent to the question - yes, the BB drop will be the same in relation to the axles, but the axles will be closer to the ground, therefore so will the pedals.
    How much lower is the question.

    Most people when putting non-plus tires on a frame designed for plus tires go to a bigger wheel size to compensate; ie for a 27.5+ bike, you'd go with 29" wheels for 'skinny' tires.
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  5. #5
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    Very pertinent. A new Santa Cruz 5010, a bike that comes with 2.3" tires and similar travel, has a BBD of 24mm in the low setting. So a bike with 25mm and 2.5/2.4" tires will not be out of the norm. It will be low, yes, but not stupid low.

    Anyways to directly answer OP's height concern this quote is from the the pinkbike review of the Mojo 3:

    The Mojo 3 is pictured here with 2.8'' wide tires from Schwalbe, and that's also the configuration that I spent most of my time on, but Ibis' Scot Nicol does stress that the new bike is far from being a plus-only machine. ''We’ve found that the [width] numbers printed on tire sidewalls mean very little when it comes to their height,'' Nicol explained after experimenting with just how much of a difference there is in diameter between plus and standard 27.5'' tires. ''The Schwalbe and Maxxis 2.8s are only 0.15” taller in section height than a 2.3'' tire, whereas 3.0'' tires are 0.4” taller.

  6. #6
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    Wink

    Lots of good answers here

    Tires are not the most expensive parts on a bike, so I will give it a try when I get home.

    Rocky Mountain also have the Ride-9 chip "thingy" to help me as well. Some positions give higher bottom bracket height.

    Meanwile I have been on google: Since I am kinda running a low pressure in the Rekon tires, I am thinking the bottom bracket height might not change that much... Those plus tires are kind of squishy... The whole point of lots of grip with plus tires, right?

    So, for me, it will be fun to try some other tires. So, I get to know more about pros and cons of tire sizes.

    To the changing with 29er wheels: according to some review I read, the first Pipeline series can not fit 29 inch wheels. Wonder if the newer plus bike models that can fit both 27.5 and 29 wheels can use smaller 27.5 tires like the one I will try to fit.

    Anyway, thanks!!! Awesome!

  7. #7
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    Quote Originally Posted by ac1000 View Post
    Very pertinent. A new Santa Cruz 5010, a bike that comes with 2.3" tires and similar travel, has a BBD of 24mm in the low setting. So a bike with 25mm and 2.5/2.4" tires will not be out of the norm. It will be low, yes, but not stupid low.[/I]
    And that answers the other question on my last post as well

  8. #8
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    You might need to consider the width of your rims as well. A 2.4 on a 40mm rim, for example, may not work so well. 40mm rims usually have 2.6 or larger tires. What is the inner width of the rim?

  9. #9
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    35mm, so they should be fine for Maxxis WT tires.

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